WATER QUALITY IMPROVEMENT AND METHANE EMISSIONS

FROM TROPICAL AND TEMPERATE WETLANDS

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the

Graduate School of The Ohio State University

By

Amanda M. Nahlik, B.A., M.S.

Environmental Science Graduate Program

The Ohio State University

2009

Dissertation Committee:

Dr. William J. Mitsch, Advisor

Dr. Nicholas T. Basta

Dr. Richard P. Dick

Dr. Jay F. Martin

Copyright by

Amanda M. Nahlik

2009

ABSTRACT

Wetlands are important ecosystems in our landscape because of the broad array of ecosystem services they provide to humans and the environment. Wetlands have unique biotic and abiotic chemical interactions among soil, water, and vegetation that, combined with long retention times that are characteristic of wetlands, allow for nutrients, metals, and organic pollutants to be removed from the water column, resulting in cleaner water.

The same characteristics that make wetlands so efficient at improving water quality also provide anaerobic conditions and organic substrate that is optimal for methanogenesis,

the microbial production of the greenhouse gas (GHG) methane (CH4). The objective of this dissertation is to investigate the biogeochemistry, specifically water quality

improvement and CH4 emissions, of natural and created wetlands in tropical and temperate climates.

Five tropical treatment wetlands dominated by floating aquatic plants and constructed to deal with a variety of wastewaters were compared for their effectiveness in treating organic matter and nutrients in the Parismina River Basin in eastern Costa Rica.

Wastewaters were from a dairy farm, a dairy processing plant, a banana paper plant, and a landfill. Four of the five wetland systems were effective in reducing nutrient levels of effluents before water was discharged into rivers. Ammonia nitrogen (N) levels in water entering most wetlands were considerably higher than ambient (i.e., riverine) levels;

ii concentrations were reduced by as much as 92% in the wetlands, which retained, at a

−2 −1 maximum, more than 166 g NH4-N m y . Nitrate N removal occurred in low concentrations in the inflows (less than 1 mg-N L−1). Phosphate phosphorus (P) was effectively reduced through the wetlands (92 and 45% reductions through dairy farm wetlands, 83% reduction through banana paper wetlands, and 80% reduction through dairy processing wetlands). Retention of phosphate ranged from 0.1 to 10.7 g-P m−2 year−1 in the treatment wetlands. Dissolved oxygen in the wetland outflows were ≤2 mg

L−1 in three of the sampled wetlands, most likely a result of the abundant free-floating macrophytes that sheltered the water from diffusion and shaded aquatic productivity.

The efficacy of these created wetlands to treat effluents from different sources varied, and modified wetland designs or active management may be necessary to further improve water quality. Recommendations on tropical wetland design and management are presented, as are suggestions for implementing an ecological engineering approach with farmers in Central America.

Wetlands are one of the largest natural sources of the greenhouse gas CH4 released to the atmosphere. Despite the fact that a large percentage of wetlands occur in

tropical latitudes, CH4 emissions from natural tropical wetlands are not well understood.

The objective this research was to compare wetland CH4 emissions from three natural tropical wetlands located in different climatic and ecological areas of Costa Rica. There were three distinct tropical wetland ecosystems: 1) a humid flow-through wetland slough with high mean annual temperatures (25.9 ºC) and precipitation (3700 mm yr-1); 2) a stagnant rainforest wetland with high mean annual temperatures (24.9 ºC) and precipitation (4400 mm yr-1); and 3) a seasonally wet riverine wetland with very high

iii mean annual temperatures (28.2 ºC) and lower mean annual precipitation (1800 mm yr-1).

CH4 emission rates measured from sequential gas samples using non-steady state plastic chambers during 6 sampling periods over a 29-month period from 2006-2009 were higher than most rates previously reported for tropical wetlands. Means (medians) were 356

-2 -1 (116), 906 (145), and 1004 (371) mg CH4-C m d for the three sites, with highest rates

(p = 0.000) occurring at the seasonally flooded wetland site compared to the humid sites.

Highest CH4 emissions occurred when water levels were between 30 and 50 cm. We

-1 estimate that Costa Rican wetlands produce about 1.3 Tg yr of CH4, or approximately 1

percent of global tropical wetland emissions. Elevated CH4 emissions at the seasonally wet/warmer wetland site suggests that some humid tropical wetlands of Central America

may emit more CH4 if temperatures increase and precipitation decreases with climate change.

There have been few studies of CH4 emissions in created and restored wetlands.

We measured seasonal and spatial patterns of CH4 emissions over a two-year period

(2006-08) from two 12 to 14-year-old created wetlands in central Ohio, one initially planted and the other allowed to self-colonize, to determine how season, hydrology, and the original wetland creation approach influence those emissions. Median (mean)

spring/summer CH4 emissions for the planted and self-colonized wetlands were 56 (84)

-2 -1 and 111 (287) mg CH4-C m d for Wetland 1 and Wetland 2 respectively, while autumn

-2 -1 and winter emissions were considerably lower (11 (28) and 24 (66) CH4-C m d , respectively). Overall, the two created wetlands were different with respect to CH4 emissions, with the plant self-colonized wetland emitting higher annual CH4 emissions

-2 -1 (median and mean emissions of 19 and 68 g CH4-C m y , respectively) than the planted iv -2 -1 wetland (median and mean emissions were 6 and 17 g CH4-C m y , respectively). Since hydrology and soil/water temperature were identical for the two wetlands, we hypothesize that differences in carbon accumulation due to higher net primary

productivity in the self-colonized wetland may be causing higher CH4 emissions in that wetland. Net primary productivity in the self-colonized wetland was higher 7 out of 11

years prior to the study. Mean CH4 emissions from the two created wetlands were 21 and

-2 -1 83 % of the CH4 emission of 82 g CH4-C m y measured in a natural wetland in Ohio with similar hydrologic patterns. Annual CH4 emissions increased at a higher rate in the planted wetland than in the self-colonized wetland over a four-year period with increases

-2 -1 of 4 and 16 g CH4-C m y in the planted and self-colonized wetland, respectively. CH4 emissions from created wetlands in their early decades may depend as much or more on the methods used to create the wetlands (e.g. planting vs. natural colonization) as on the hydrogeomorphic conditions of the wetlands.

v

DEDICATION

To my parents, without whom I would never have had so many opportunities to get this

far, Siobhan Fennessy, who opened the great door of Wetland Ecology to me, and Eric

Emerson, who has been by my side from the start of my Ph.D., even through cold and

rainy field work and amidst tears of frustration, cheering me on all the way to the end.

vi

ACKNOWLEDGMENTS

The research conducted for this dissertation would not have been possible without the help of my mentors, colleagues, friends, and family. The generosity of the community around me to lend a hand in the field, read over a manuscript, or help in the lab was constant throughout my graduate tenure at The Ohio State University.

First and foremost, I would like to acknowledge my advisor, Dr. William Mitsch, for all his insight and help during my Ph.D. I am honored to have received two degrees under Bill, and have enjoyed getting to know Bill during my time at OSU. Never have I seen the contagious enthusiasm that Bill has when it comes to wetlands. I fondly remember following Bill, machetes in hand, into the wild Reserva wetland at EARTH

University when we first learned of its existence. After the unpleasant tick-extraction that resulted from that tropical exploration, I have been more careful about my curious tendencies, but Bill, I would still follow you into [almost] any wetland! Thanks so much for all the knowledge and experience you have imparted upon me. It has been a pleasure working with you and I look forward to collaborating in the future!

My dissertation committee, Dr. Nick Basta, Dr. Richard Dick, and Dr. Jay Martin have also been helpful in providing comments on my dissertation and manuscripts and input into the initial projects. I truly enjoyed the challenges I received in both their classes and in my oral exams for my candidacy and defense.

vii Blanca Bernal has become one of my closest friends and most trusted field-mate since starting my dissertation. Blanca may have given as much blood to my project as I have, and she has been nothing less than amazing in the wetlands swarming with crocodiles, ant-infested cabins, and jungles teeming with pit vipers and spiders. Even in

Ohio, Blanca has been by my side more than anyone else in the field. Blancs, thanks for all your help, company, and friendship.

Dr. Anne Altor, friend and colleague, has been especially helpful and taught me much of what I needed to know to run the gas chromatograph and sample for methane.

Her wisdom and encouragement continued even after she finished her doctorate, and it has been greatly appreciated. Like a good friend, Anne was almost always able to convince me to step away and take a break, for a caipirinha or a climb, which is probably why I still have my sanity!

Eric Emerson often helped me in the field on those early mornings when I could not convince others to get out of bed and on the cold winter days on Lake Erie. I am thankful for all his help in the field and at home, keeping things running smoothly when I was tied to work.

Other friends and colleagues that have helped in numerous ways throughout the years in the field and lab in both Ohio and Costa Rica include Angela Adams, Dr. Herbert

Arrieta, Jackie Batson, Dr. Marlon Breve, Emily Castellanos, Marinela Castro, Andrew

Cerrato, Kyle Chambers, Chris Cooley, Eric Emerson, Dr. Dan Fink, Dr. Siobhan

Fennessy, Paul Hartzog, Dr. Carlos Hernández, Dr. Maria Hernández, Chen Huang, Kurt

Keljo, Dr. Bert Kohlmann, Matt McCaw, Lukas Moe, Maria Muñoz, Monica Noon,

Denis Odokonyro, Abby Rokosch, Bryan Smith, Dr. Keunyea Song, Kay Stefanik, Dr.

viii Julio Tejada, Evan Waletzko, Dr. Jane Yoemans, Ryan Young, Charissa Younge, and Dr.

Li Zhang.

Lynn McCreedy was a huge help during the final stages of my dissertation. As the lab manager, Lynn helped keep the gas chromatograph (and all the equipment) running, standards and gases stocked, and supplies organized. Lynn really went above and beyond when it came to my crunch-time, and freed me from running water samples so I could write this dissertation and prepare for my defense. There is no better gift than the gift of time, so thank you Lynn!

Finally, I would like to give special thanks to my father, Richard Nahlik, for spending his vacation with me in Costa Rica, sampling for methane. There are few people that were able to experience what I did in Costa Rica, and I am so glad that Dad was one of them. Staying in the cabins of Palo Verde and hiking to the top of “La Roca” really took me back to my childhood, when we used to climb walls and camp with Indian

Princesses. Spending time with Dad in Costa Rica was an experience I will always cherish.

ix

VITA

October 1, 1980...... Born – Hinsdale, Illinois

2000...... Field Research Assistant, Illinois Natural History Survey, Lake Michigan Biological Station, Zion, IL

2001...... School for Field Studies, Resource Management Program, South Caicos Island, British West Indies

2001 - 2002 ...... Summer Science Scholar, Kenyon College, Gambier, OH

May 18, 2002 ...... B.A. Biology, Environmental Studies Concentration, Kenyon College, Gambier, OH

2003 - 2009 ...... Graduate Teaching and Research Associate, Olentangy River Wetland Research Park, The Ohio State University, Columbus, OH

December 11, 2005 ...... M.S. Environmental Science Graduate Program, The Ohio State University, Columbus, OH

August 30, 2009...... Ph.D. Environmental Science Graduate Program, The Ohio State University, Columbus, OH

x PUBLICATIONS

Peer-Reviewed Journal Articles

Mitsch, W.J., A.M. Nahlik, P. Wolski, L. Zhang, B. Bernal, and L. Ramberg. In press. Tropical wetlands: Seasons, hydrologic pulsing, and carbon biogeochemistry. Wetlands Ecology and Management.

Mitsch, W.J., L. Zhang, D.F. Fink, M.E. Hernandez, A.E. Altor, C.L. Tuttle, and A.M. Nahlik. 2008. Ecological engineering of floodplains. Ecohydrology & Hydrobiology 8: 139-147.

Mitsch, W.J., J. Tejada, A.M. Nahlik, B. Kohlmann, B. Bernal, and C.E. Hernández. 2008. Tropical wetlands for climate change research, water quality management and conservation education on a university campus in Costa Rica. Ecological Engineering 34: 276-288.

Nahlik, A.M. and W.J. Mitsch. 2008. Effect of river pulsing on sedimentation and nutrients in created riparian wetlands. Journal of Environmental Quality 37: 1634- 1643.

Nahlik, A.M. and W.J. Mitsch. 2006. Tropical treatment wetlands dominated by free-floating macrophytes for water quality improvement in Costa Rica. Ecological Engineering 28: 246-257.

Professional Reports/Report Chapters

Mitsch, W.J., L. Zhang, and A.M. Nahlik. 2005. Designing a regeneration zone for the Cuyahoga River Valley. Report to the Rocky Mountain Institute. Olentangy River Wetland Research Park, The Ohio State University, Columbus, 72 pp.

Nahlik, A.M. 2004. Spatial and temporal changes of soil properties in the experimental wetlands in 2003. Olentangy River Wetland Research Park Annual Report, The Ohio State University, Columbus, pp. 85-92.

Presentations*, Posters** and Published Abstracts

*Nahlik, A.M. and W.J. Mitsch. 2009. Effect of season, hydrology, and productivity on seasonal methane emissions in two created wetlands in Ohio. Society of Wetland Scientists 30th Annual Meeting, June 22-26. Madison, WI.

xi

Mitsch, W.J., A.M. Nahlik, and B. Bernal. 2009. Tropical wetlands: Climate change and carbon. Abstracts, Society of Wetland Scientists 30th Annual Meeting, June 22-26. Madison, WI.

*Nahlik, A.M. and W.J. Mitsch. 2008. Effects of hydrology and climate on methane emissions from freshwater flow-through wetlands. Society of Wetland Scientists 29th Annual Meeting, May 25-29, 2008. Washington DC.

Mitsch, W.J., L. Zhang, D. Fink, A.M. Nahlik, C. Tuttle, A. Altor, and M. Hernandez. 2008. Hydrologic pulsing and riparian freshwater wetlands. Abstracts, Society of Wetland Scientists 29th Annual Meeting, May 25-29, 2008. Washington DC.

*Nahlik, A.M. 2008. Effects of hydrology and climate on methane emissions from freshwater flow-through wetlands. Buckeye Ecologists Inaugural Graduate Research Symposium, March 26, 2008. The Ohio State University, Columbus, OH.

**Nahlik, A.M. and W.J. Mitsch. 2007. Methane emissions in tropical wetlands. Society of Wetland Scientists 28th Annual Meeting, June 10-15, 2007. Sacramento, CA.

Mitsch, W.J., L. Zhang, and A.M. Nahlik. 2007. Ecological restoration in Midwestern USA: designing a regeneration zone for the Cuyahoga River Valley. Abstracts, EcoSummit 2007, Ecological Complexity and Sustainability: Challenges & Opportunities for 21st Century’s Ecology, May 22-27, 2007. Beijing, PR China.

Mitsch, W.J, A.M. Nahlik, P. Wolski, K.B. Mfundisi, L. Zhang, W. R.L. Masamba, B. Bernal, and P. Huntsman-Mapila. 2007. Tropical wetlands: Seasons, hydrologic pulsing and biogeochemistry. Abstracts, Society of Wetland Scientists 28th Annual Meeting, June 10-15, 2007. Sacramento, CA

Mitsch, W.J., L. Zhang, M.E. Hernandez, A.E. Altor, A.M. Nahlik, C.L. Tuttle, D.F. Fink, and C. J. Anderson. 2006. Importance of hydrologic pulsing on the water quality function of wetlands in Midwestern USA. Proceedings, American Water Resources Association Annual Meeting, November 9, 2006. Baltimore, MD.

*Mitsch, W.J. and A.M. Nahlik. 2006. Wetland research in Costa Rica: collaboration with EARTH University. EARTH University/Ohio State University Collaborative Research Symposium, March 21, 2006. EARTH University, Costa Rica.

*Nahlik, A.M. and W.J. Mitsch. 2005. Effects of river pulsing on sedimentation patterns in created wetlands. Ecological Society of America 90th Annual Meeting, August 12-18, 2005. Montréal, Canada.

xii

**Nahlik, A.M., S.L. Lansing, J.F. Martin, and W.J. Mitsch. 2005. Wetland creation for water quality improvement in Costa Rica. American Ecological Engineering Society 5th Annual Meeting, May 18-20, 2005. The Ohio State University, Columbus, OH.

**Nahlik, A.M. and M.S. Fennessy. 2002. Using amphibians as ecological indicators: biological integrity in natural, restored, and created wetlands. Society of Wetland Scientists 23rd Annual Meeting, June 2-7, 2002. Lake Placid, NY.

**Nahlik, A.M. and M.S. Fennessy. 2002. Using amphibians as ecological indicators: biological integrity in natural, restored, and created wetlands. 16th National Conference for Undergraduate Research, April 25-27, 2002. University of Wisconsin, Whitewater, WI.

FIELD OF STUDY

Major Field: Environmental Science

Specialization: Wetland Ecology and Biogeochemistry

xiii

TABLE OF CONTENTS

Page

Abstract...... ii Dedication...... vi Acknowledgments...... vii Vita...... x

List of Tables ...... xvii List of Figures...... xix

CHAPTERS:

1. INTRODUCTION ...... 1 1.1 Goals and objectives ...... 2 1.2 Tropical treatment wetlands and water quality...... 3 1.3 Methane emissions from tropical and temperate wetlands...... 5 1.4 References...... 7

2. TROPICAL TREATMENT WETLANDS DOMINATED BY FREE-FLOATING MACROPHYTES FOR WATER QUALITY IMPROVEMENT IN COSTA RICA.12 2.1 Abstract...... 12 2.2 Introduction...... 13 2.3 Methods...... 15 2.3.1 Site description...... 15 2.3.2 Wetland morphology and hydrology ...... 16 2.3.3 Wastewater characterization ...... 17 2.3.4 Water sampling and analysis ...... 17 2.3.5 Statistical analysis...... 18 2.4 Results...... 19 2.4.1 Wetland morphology and hydrology ...... 19 2.4.2 Wetland vegetation ...... 20 2.4.3 Water quality...... 21 2.4.3.1 Oxygen-demanding substances...... 21 2.4.3.2 Dissolved oxygen...... 22 2.4.3.3 Suspended material ...... 22 2.4.3.4 Nutrients...... 23 xiv 2.5 Discussion...... 24 2.5.1 Water quality improvement by tropical treatment wetlands...... 24 2.5.2 Hydraulic loading and nutrient retention rates...... 25 2.5.3 Free-floating macrophytes ...... 27 2.5.4 Management and design considerations ...... 29 2.5.5 Using treatment wetlands in tropical regions...... 31 2.6 Acknowledgments...... 32 2.7 References...... 33

3. EFFECT OF CLIMATE ON METHANE EMISSIONS FROM TROPICAL FRESHWATER WETLANDS IN COSTA RICA...... 48 3.1 Abstract...... 48 3.2 Introduction...... 49 3.3 Materials and methods ...... 51 3.3.1 Study sites ...... 51 3.3.2 Methane emission sampling...... 53 3.3.3 Meteorological data ...... 55 3.3.4 Processing and analysis...... 55 3.3.5 Statistical analysis...... 57 3.4 Results...... 58 3.4.1 Climate, soil temperature, and hydrology...... 58 3.4.2 Wetland methane emissions...... 59 3.4.3 Diurnal methane emissions...... 60 3.4.4 Spatial methane emissions ...... 61 3.4.5 Relationship of methane emissions to physiochemistry ...... 62 3.5 Discussion...... 63 3.5.1 Tropical methane emissions and climate ...... 63 3.5.2 Tropical methane emissions and hydrology ...... 64 3.5.3 Importance of carbon ...... 65 3.5.4 Spatial variability within wetlands...... 67 3.5.5 Comparison of methane emissions ...... 68 3.5.6 Tropical methane emission rates...... 69 3.5.7 Changes in tropical methane emissions as a result of climate change ...... 70 3.6 Conclusions...... 70 3.7 Acknowledgments...... 71 3.8 References...... 71

4. EFFECT OF SEASON, HYDROLOGY AND CUMULATIVE PRODUCTIVITY ON METHANE EMISSIONS IN TWO 13-YEAR-OLD CREATED WETLANDS 87 4.1 Abstract...... 87 4.2 Introduction...... 88 4.3 Methods...... 91 4.3.1 Study site...... 91 4.3.2 Experimental design...... 92 xv 4.3.3 Methane sampling...... 93 4.3.4 Gas analysis ...... 95 4.3.5 Hydrology ...... 96 4.3.6 Wetland macrophyte productivity...... 96 4.3.7 Statistical analysis...... 96 4.4 Results...... 97 4.4.1 Seasonal patterns and effect of soil temperature...... 98 4.4.2 Effects of hydrology ...... 99 4.4.3 Natural reference wetland...... 100 4.5 Discussion...... 101 4.5.1 Effects of soil temperature (season) and water depth ...... 101 4.5.2 Comparison with past studies at the same created wetlands...... 102 4.5.3 Methane emissions and wetland macrophyte productivity...... 103 4.5.4 Comparison with natural wetland emissions ...... 106 4.6 Conclusions...... 107 4.7 Acknowledgments...... 108 4.8 References...... 109

5. CONCLUSIONS ...... 125 5.1 Water quality improvement and tropical treatment wetlands...... 125 5.2 Methane emissions from natural tropical wetlands ...... 126 5.3 Methane emissions from created temperate wetlands ...... 127 5.4 Integrative conclusions ...... 128

Bibliography ...... 129

Appendix A: Raw Laboratory Data from Tropical Treatment Wetlands in Costa Rica..146 Appendix B: Raw In-Field Data from Tropical Treatment Wetlands in Costa Rica...... 152 Appendix C: Raw Methane Emission Data from Tropical Wetlands in Costa Rica ...... 158 Appendix D: Raw Methane Emission Data from Temperate Wetlands in Ohio...... 167

xvi

LIST OF TABLES

Table Page

2.1. Morphology and hydrology of wetland systems in this study...... 38

2.2. Condition and description of reference sites used in this study ...... 38

2.3. Percent change by concentration and mass (all reductions, except dissolved oxygen) of water quality indicators in the wetlands used in this study. Numbers in parentheses represent the associated p-value for the reduction from inflow to outflow...... 39

2.4. Rates of nutrient and oxygen-demanding substance inflow, outflow, and removal (g m-2 year-1) in the treatment wetlands ...... 40

3.1. Description of characteristics of wetlands included in this study. Annual rainfall is reported as mean annual precipitation from 1999 through 2008 ± standard error. Note: 1 ha = 10,000 m2 ...... 77

3.2. Methane emissions and supporting environmental data by wetland site (EARTH, La Selva, Palo Verde) and sampling station (UP = upland, S = shallow wetland, -2 -1 D = deep wetland). Methane is reported as mg CH4-C m h for morning (AM) and afternoon (PM) averages. The daily mean of methane emission is reported -2 -1 as mg CH4-C m d . All values are means ± SE...... 77

3.3. Methane (CH4) emissions measured for several tropical and sub-tropical wetland and river studies. Study location, biome, field measurement technique, and wetland type are reported for each study. Methane emissions are reported in -2 -1 original units from the source and in g CH4 m yr . Values are overall means or seasonal means from individual studies...... 78

-2 -1 4.1. Comparison of mean annual methane emission rates (g CH4-C m y ) measured in this study to past studies in the same experimental wetlands and other temperate wetland studies. Different hydrologic regimes during the study periods are reported...... 116

xvii 4.2. Annual net primary productivity (g-dry wt m-2 y-1) and cumulative productivity (Mg ha-1) in the experimental wetland from 1997 to 2007...... 116

A1. Nutrients, oxygen-demanding substances, and solids estimated from tropical treatment wetlands in Costa Rica...... 146

B1. In-field data, including temperature, conductivity, dissolved oxygen (DO), pH, and oxidation-reduction potential (ORP) measured from tropical treatment wetlands...... 152

C1. Raw methane emission and environmental property data from tropical wetlands in Costa Rica including EARTH (E), Palo Verde (PV), and La Selva (LS)...... 158

D1. Raw methane emission and environmental property data from temperate wetlands in Ohio including Olentangy River Wetland 1 (ORW1), Olentangy River Wetland 2 (ORW2), and Old Woman Creek (OWC)...... 167

xviii

LIST OF FIGURES

Figure Page

2.1. Hydrologic map of the study area, EARTH University, located in Limon Province, eastern Costa Rica. Numbers represent the following sampling sites: (1) Lecheria wetlands, (2) LaPA wetland, (3) Planta de Papel wetland, (4) Relleno Sanitario wetland, (5) Empacadora Bananos, and (6) Dos Novillos River. Black areas represent neighboring countries (Nicaragua to the north and Panama to the south), and shaded area within Costa Rica represents Limon Province...... 41

2.2. General morphology and vegetation cover of: (a) Lecheria 1-2 wetlands, (b) Lecheria 3-4 wetlands, (c) LaPA wetland, (d) Planta de Papel wetland, and (e) Relleno Sanitario wetland. Vegetation surveys were conducted in August 2004, at the beginning of the study. Routine maintenance (i.e., dredging) was being performed on the second basin of the Planta de Papel wetlands during the survey; therefore, a survey was not conducted for this wetland. Vegetation is listed in order of most dominant to least common. Wetlands are orientated so inflows are on the top and outflows are on the bottom...... 42

−1 2.3. Oxygen-demanding substances (mg O2 L ), including: (a) biochemical oxygen demand and (b) chemical oxygen demand in inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows...... 43

2.4. Dissolved oxygen concentrations (mg L−1) in inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows...... 44

xix

2.5. Turbidity (NTU) of inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows...... 45

2.6. Nutrient concentrations, including: (a) ammonia–nitrogen (mg N L−1), (b) nitrate–nitrogen (mg N L−1), and (c) phosphate–phosphorus (µg P L−1), of inflows (dark gray bars) and outflows (light gray bars) in treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows. Note that graphs (a) and (c) are on a log scale...... 46

2.7. Relationship between nutrient and oxygen-demanding substance reduction (g m−2week−1) and hydraulic loading rate. Polynomial curves are reported with R2 value. Points represent mean reduction for the five surface-flow wetlands used in this study (Lecheria 1-2, Lecheria 3-4, LaPA, Planta de Papel, and Relleno Sanitario wetlands)...... 47

3.1. Study location sites in Costa Rica and their associated watersheds (shaded in grey)...... 79

3.2. Methane gas-sampling chamber design...... 80

3.3. Environmental variables including mean water level (cm), mean soil temperature at 5 cm (°C), mean air temperature (°C), total monthly precipitation (mm mo-1), -2 -1 and mean (lines) and median (markers) methane flux (mg CH4-C m h ) for a) EARTH, b) La Selva, and c) Palo Verde wetlands. Error bars on environmental variable data represent standard error, while error bars on the median methane emissions represent the maximum and minimum limits. Note that methane emissions are reported on a log scale...... 81

3.4. Mean (horizontal lines) and median (circles) wetland methane emission rates -2 -1 (mg CH4-C m d ) for each wetland included in this study. Vertical lines represent minimum and maximum values. Different letters indicate significant differences in medians between groups. Note that methane emissions are reported on a log scale...... 84

xx 3.5. a) Mean air temperature (°C), b) mean soil temperature at 5 cm (°C), c) mean water level (cm), and d) mean (lines) and median (circles) wetland methane -2 -1 emission rates (mg CH4-C m d ) for two separate transects (1 and 2) at EARTH (E), La Selva (LS), and Palo Verde (PV) wetlands. Error bars represent minimum and maximum limits for methane and standard error for environmental conditions. Different letters indicate significant differences between groups using median methane emissions and environmental means...... 85

3.6. Relationship between methane emissions and average water level for each of this Costa Rican wetland study. Line is a second-order polynomial regression through solid data points...... 86

4.1. Methane-sampling chamber site locations in Wetland 1 (planted) and Wetland 2 (self-colonizing) at the Olentangy River Wetland Research Park. Arrows indicate the inflows and outflows of the wetlands, with water moving from north to south. Light grey circles correspond to upland, dark grey circles correspond to shallow wetland, and black circles correspond to deep wetland chamber locations. Deepwater zones are designated by large ovals, and lines represent boardwalks...... 117

4.2. Median (open circles) and mean (horizontal bars) of annual methane emissions -2 -1 (g CH4-C m y ) for planted Wetland 1 and self-colonizing Wetland 2. Methane emissions rates are reported next to the appropriate marker. Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between methane emissions of the same wetland...... 118

4.3. Seasonal patterns of soil temperature (°C), chamber water level (cm), and -2 -1 methane emissions (mg CH4-C m h ) for each sampling period in planted Wetland 1 and self-colonizing Wetland 2. Error bars on mean soil temperatures represent S.E. Median methane emissions are designated by the solid marker, mean methane emissions are designated by the horizontal bar, and error bars represent the minimum and maximum methane emissions...... 119

4.4. Median (open circles) and mean (horizontal bars) seasonal methane emissions -2 -1 (mg CH4-C m d ) for a) Wetland 1 and b) Wetland 2. Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between median seasonal methane emissions of the same wetland...... 120

4.5. Relationship between methane emission rates and mean soil temperature for planted Wetland 1 (black dots), self-colonizing Wetland 2 (grey diamond), and natural wetland at Old Woman Creek (open square) for each sampling period. Solid, dotted, and dashed trend lines are for Wetland 1, Wetland 2, and Old Woman Creek, respectively. Boxes at 10°C demonstrate differences in methane emissions between wetlands at that temperature...... 121 xxi

4.6. Median (open circles) and mean (horizontal bars) methane emissions (mg CH4-C m-2 d-1) for upland, shallow water, and deep water sampling sites in the created wetland sites (Wetlands 1 and 2 at the ORWRP) compared to a natural reference wetland (Old Woman Creek). Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between methane emissions of the same wetland...... 122

4.7. Estimated annual methane emission rates for experimental wetlands at the Olentangy River Wetland Research Park: a) emission rates for planted (Wetland 1) and self-colonizing wetland (Wetland 2) by year for 2004 to 2008 and b) relationship between methane emissions and cumulative macrophyte net primary productivity (Mg ha-1) for 2004 through 2007. Trend lines for a) represent each wetland and trend line for b) represents all points. 2004 and 2005 data are from Altor (2007) and Altor and Mitsch (2008). Cumulative productivity data are from Mitsch et al. (2009)...... 123

4.8. Estimated patterns of methane emission development in planted (black line) and self-colonized (grey line) created wetlands at the Olentangy River Wetland Research Park over time. Circular markers represent mean methane emissions from 2004-2007 are centered on year 12 for the planted wetland and the self- colonized wetland. Short bolded solid lines are the slope of methane emission over time from Figure 4.7a. Natural wetland emissions are based on those measured at Old Woman Creek wetland in Ohio and are assumed to be in steady state. The shaded area between the lines represents methane emissions that are potentially avoided by planting...... 124

xxii

CHAPTER 1: INTRODUCTION

Wetlands are particularly important ecosystems in our landscape because of the broad array of ecosystem services they provide to humans and the environment, including flood prevention, hurricane storm abatement, nutrient recycling, carbon sequestration, recreational space, and habitat (Mitsch et al., 2009). Perhaps one of the most valuable benefits that wetlands offer is water quality improvement. The unique biotic and abiotic chemical interactions between soil, water, and vegetation and long retention times that are characteristic of wetlands allow for nutrients, metals, and organic pollutants to be removed from the water column, resulting in cleaner water (Mitsch, 1995; Ewel, 1997;

Postel and Carpenter, 1997; Whigham and Jordan, 2003). Humans have utilized the ability of wetlands to clean water by constructing wetlands all over the world to treat wastewater from agricultural and industrial production. Despite the encouragement of the use of treatment wetlands in small villages in developing countries (Denny, 1997;

Solano et al, 2004), such as those in Central America, the implementation and success of treatment wetlands in these regions have not been thoroughly investigated. Tropical treatment wetland studies have been largely limited to Africa (Nzengy’a and Wishitemi,

2001), Thailand (Koottatep and Polprasert, 1997; Kantawanichkul et al., 1999;

Kantawanichkul et al., 2009), and Australia (Greenway, 1997).

1 The same characteristics that make wetlands so efficient at improving water quality also create anaerobic conditions and provide organic substrate optimal for

methanogenesis, the microbial production of the greenhouse gas methane (CH4).

Wetlands are the largest natural source of methane emissions to the atmosphere, constituting about 25 percent of the total emissions (Whalen, 2005; IPCC, 2007). Much of the methane research has focused on boreal wetlands (Moore and Knowles, 1990;

Shannon and White, 1994; Moosavi et al., 1996; Rask et al., 2002; Huttunen et al., 2003), natural temperate wetlands (Wilson et al., 1989; Huang et al., 2005; Rose and Crumpton,

2006; Smemo and Yavitt, 2006), and highly-managed created wetlands, such as rice paddies (Husin et al., 1995; Naser et al., 2007; Gogoi et al., 2008). Methane emissions from natural tropical wetlands and created temperate wetlands have been scarcely investigated by researchers despite the potentially high impact these wetlands could have on climate change.

1.1 Goals and objectives

The goal of this dissertation is to investigate the biogeochemistry of natural and created wetlands in tropical and temperate climates and narrow some of the information gaps that remain, specifically on tropical wetland water quality improvement and methane emissions from tropical and temperate wetlands. Three separate studies were conducted. The objectives of these studies are as follows:

1) Determine the efficacy of treatment wetlands in the tropics to improve water

quality of four different waste streams (Chapter 2);

2 2) Compare methane emissions from natural tropical wetlands located in

different climatic zones in Costa Rica (Chapter 3);

3) Evaluate the effects of season, hydrology, and cumulative productivity on

methane emissions from created temperate wetlands in Ohio (Chapter 4).

Research was conducted at three wetland sites in Costa Rica and two wetland sites in

Ohio, USA. Research for the tropical treatment wetland study took place in five treatment wetlands located at EARTH University in Costa Rica. This 3,300 ha tropical campus is located on the eastern, Caribbean plain of Costa Rica and houses several small agricultural operations and production facilities for dairy and banana paper. Methane emissions were measured at a 116-ha natural wetland slough on the EARTH campus, at a

3-ha wetland in a mature tropical rain forest at La Selva Biological Station in mountainous central Costa Rica, and at a 2,000-ha riverine wetland at Palo Verde

Biological Station on the western Pacific coast of Costa Rica. In Ohio, two 1-ha experimental wetlands created in 1994 at the Wilma H. Schiermeier Olentangy River

Research Park on The Ohio State University campus, Columbus, OH, and a 56-ha natural wetland located at Old Woman Creek State Nature Preserve on Lake Erie, Huron, OH, were used for a temperate zone wetland methane emission study.

1.2 Tropical treatment wetlands and water quality

Treatment wetlands are engineered wetland systems, with either subsurface flow or surface flow, for the specific purpose of improving water quality (Kadlec and Knight,

1996; Kadlec and Wallace, 2009). By engineering a treatment wetland with a specific loading rate, retention time, soil type, and vegetation community, particular nutrients,

3 metals, or organic pollutants may be removed from the water column (Thullen et al.,

2005). Tropical treatment wetlands may have an advantage over those from other climates because of a year-round growing season, supporting vegetation that aids in chemical and nutrient cycling and transformation (Thullen et al., 2005; Maine et al.,

2009). Treatment wetlands in the United States have been shown to effectively remove contaminants from agricultural and industrial wastewater. Stone et al. (2004) reported total nitrogen reductions of 30% in treatment wetlands receiving swine lagoon effluent

(Stone et al., 2004). Mean reductions for inorganic nutrients ranged from 42-48% in constructed wetlands treating livestock wastewater (Knight et al., 2000). Maine et al.

(2006) reported that metals, such as Cr, Ni, Zn, and Fe, were reduced up to 95% by treatment wetlands receiving industrial wastewater.

While treatment wetlands have been proven effective in temperate regions, tropical treatment wetlands, which function under drastically different temperatures and vegetation communities than temperate treatment wetlands, have not been thoroughly investigated. Kantawanichkul et al. (2009) showed that vertical flow constructed wetlands in Thailand have the capacity to treat wastewater for nutrients, but design must be taken into careful consideration for achieve effective reductions. Greenway (2005) found that constructed wetlands could be effectively used in arid subtropical Australia to polish reclaimed water for reuse but suggests wetlands should be designed to minimize mosquito populations, which is a large concern in tropical regions. Few studies in

Central America before ours have been published in the peer-reviewed literature in regard to design and effectiveness of treatment wetlands.

4 1.3 Methane emissions from tropical and temperate wetlands

Methanogenesis occurs under highly anaerobic conditions found in many wetlands. The amount of methane produced has been linked to the amount of available carbon in the soil, soil temperatures, and soil redox potential in laboratory studies (Wang et al., 1997; Segers, 1998; Yu et al., 2001); however, the microbial processes of methanogenesis and methane oxidation are quite complex and affected by a number of factors in the field, resulting in high spatial and temporal variability in wetland methane emission rates that difficult to accurately predict. For example, Wachinger et al. (2000) reported large differences in methane production from soil cores extracted within 1 m of each other, with variability sometimes exceeding 100% of the standard deviation. Others have reported high spatial and temporal variability in methane production on the scale of several orders of magnitude both within and among wetland sampling sites (Moore and

Knowles, 1990; Adrian et al., 1994; Chen et al., 2009). Therefore, it is not surprising that methane production from wetlands is quite variable in the literature and ranges over three orders of magnitude from 0.12 to 210 mg-C m-2 h-1 (Mitsch and Wu, 1995; Snyder, 2002;

Hadi et al., 2005).

Despite the fact that up to 40 percent of the estimated 8 million km2 of global wetlands are located in tropical climates (Mitsch and Gosselink, 2007), few natural tropical wetlands have been studied in regards to methane emissions. Recent estimates

-1 suggest that wetlands may contribute as much as 180 Tg CH4 yr , with 76% of that (138

-1 Tg CH4 yr ) coming from tropical wetlands (Bergamaschi et al., 2007; Mitsch et al., in press); however, these estimates come from relatively few wetland field studies considering the variability of methane emissions. Some of the most prominent research

5 concerning tropical methane emissions has stemmed from the Amazon River basin.

Using non-steady state chambers, such as those described in Chapters 3 and 4, methane

-2 -1 emissions, measuring between 10 and 215 g CH4-C m y were collected from open water lakes, flooded forests, and floating macrophyte mats from various areas of the

Amazon (Bartlett et al., 1998; Devol et al., 1998). Based upon these studies, Melack et al. (2004) used remote sensing to estimate methane emissions from the entire floodplain

-2 -1 of the Amazon River basin at 4 g CH4-C m y . While it is important to measure methane in different wetland systems because of the dynamic nature of methane, the

Amazon River basin is an exceptionally unique pulsing system and not necessarily representative of tropical wetlands as a whole. Other tropical wetland methane emissions

have been measured in highly managed wetlands, such as rice paddies (26-301 g CH4-C m-2 y-1; Banker et al., 1995; Singh et al., 1999; Hadi et al., 2005), riverine and riparian

-2 -1 wetlands (116-593 g CH4-C m y ; Singh et al., 2000; Yu et al., 2008), and oxbow

-2 -1 wetlands (1-386 g CH4-C m y ; Boon and Mitchell, 1995). The most similar tropical wetland ecosystems studied to those in our Costa Rica study (Chapter 3) in both physical character and methane emissions are New Guinea sloughs, with estimated emissions of

-2 -1 494-788 g CH4-C m y (Snyder, 2002).

Although tropical wetlands may have higher annual methane emissions than those in temperate regions due to their year-long growing season and high productivity, methane emissions from created and restored wetlands in the United States are also of interest (Bridgham et al., 2006). The rate of wetland creation is increasing in the United

States due to laws requiring compensatory mitigation (Dahl, 2006). Despite this fact, little research has been focused on methane emissions from created temperate wetlands.

6 -2 -1 Altor and Mitsch (2006, 2008) estimated methane emissions of 28 and 32 g CH4-C m y in 2004 and 2005, respectively, in the same study site used for research in Chapter 4.

However, even though the two wetlands were created under distinctly different initial conditions, one wetland was planted and the other was naturally colonized, methane emissions from the wetlands have not been compared to each other. The research presented in Chapter 4 compares these two wetlands and compares the rates with emissions from a similar natural wetland. This study could result in management plans for creating wetlands that result in less methane emissions.

1.4 References

Altor, A.E. and W.J. Mitsch. 2006. Methane flux from created riparian marshes: Relationship to intermittent versus continuous inundation and emergent macrophytes. Ecological Engineering 28: 224-234.

Altor, A.E. and W.J. Mitsch. 2008. Pulsing hydrology, methane emissions, and carbon dioxide fluxes in created marshes: a 2-year ecosystem study. Wetlands 28: 423- 438.

Banker, B.C., H.K. Hludze, D.P. Alford, R.D. DeLaune, and C.W. Lindau. 1995. Methane sources and sinks in rice paddy soils: relationship to emissions. Agriculture Ecosystems & Environment 53: 243-251.

Bartlett, K.B., P.M. Crill, D.I. Sebacher, R.C. Harriss, J.O. Wilson, and J.M. Melack. 1988. Methane flux from the central Amazonian floodplain. Journal of Geophysical Research 93: 1571-1582.

Bergamaschi, P., C. Frankenberg, J.F. Meirink, M. Krol, F. Dentener, T. Wagner, U. Platt, J.O. Kaplan, S. Körner, M. Heimann, E.J. Dlugokencky, and A. Goede. 2007. Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations. Journal of Geophysical Research 112: D02304, doi:10.1029/2006JD007268.

Boon, P.I. and A. Mitchell. 1995. Methanogenesis in the sediments of an Australian freshwater wetland: Comparison with aerobic decay, and factors controlling methanogenesis. FEMS Microbiology Ecology 18: 175-190. 7

Dahl, T.E. 2006. Status and trends of wetlands in the conterminous United States 1998 to 2004. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, USA.

Denny, P. 1997. Implementation of constructed wetlands in developing countries. Water and Science Technology 35: 27-34.

Devol, A.H., J.E. Richey, W.A. Clark, and S.L. King. 1988. Methane emissions to the troposphere from the Amazon floodplain. Journal of Geophysical Research 93: 1583-1592.

Ewel, K.C. 1997. Water quality improvement by wetlands. In: Daily, G.C. (ed.), Nature’s Services: Societal Dependence on Natural Ecosystems. Island Press, Washington, DC, USA. pp. 329-344.

Gogoi, N., K. Baruah, B. Gogoi, and P.K. Gupta. 2008. Methane emission from two different rice ecosystems (Ahu and Sali) at Lower Brahmaputra Valley zone of North East India. Applied Ecology and Environmental Research 6: 99-112.

Greenway, M. 1997. Nutrient content of wetland plants in constructed wetland receiving municipal effluent in tropical Australia. Water Science and Technology 35: 135- 142.

Hadi, A., K. Inubushi, Y. Furukawa, E. Purnomo, M. Rasmadi, and H. Tsuruta. 2005. Greenhouse gas emissions from tropical peatlands of Kalimantan, Indonesia. Nutrient Cycling in Agroecosystems 71: 73-80.

Huang, G., X. Li, Y. Hu, Y. Shi, and D. Xiao. 2005. Methane (CH4) emission from a natural wetland of northern China. Journal of Environmental Science and Health 40: 1227-1238.

Husin, Y.A., D. Murdiyarso, M.A.K. Khalil, R.A. Rasmussen, M.J. Shearer, S. Sabiham, A. Sunar, and H. Adijuwana. 1995. Methane flux from Indonesian wetland rice: the effects of water management and rice variety. Chemosphere 31: 3153-3180.

Huttunen, J.T., H. Nykänen, J. Turunen, and P.J. Martikaninen. 2003. Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscanidia. Atmospheric Environment 37: 147-151.

IPCC (Intergovernmental Panel on Climate Change). 2007. In: Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. Averyt, M. Tignor, and H.L. Miller (Eds.), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on

8 Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, 996 pp.

Kadlec, R.H. and R.L. Knight. 1996. Treatment Wetlands. Lewis Publishers, Boca Raton, FL, USA.

Kadlec, R.H. and S. Wallace. 2009. Treatment Wetlands, 2nd edition. CRC Press, Boca Raton, FL, USA.

Kantawanichkul, S., S. Pilaila, W. Tanapiyawanich, W. Tikampornpittaya, and S. Kamkrua. 1999. Wastewater treatment by tropical plants in vertical-flow constructed wetlands. Water Science Technology 40: 173-178.

Kantawanichkul, S., S. Kladprasert, and H. Brix. 2009. Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus. Ecological Engineering 35: 238-247.

Koottatep, T. and C. Polrasert. 1997. Role of plant uptake on nitrogen removal in constructed wetlands located in the tropics. Water Science Technology 36: 1-8.

Knight, R.L., V.W.E. Payne Jr., R.E. Borer, R.A. Clarke Jr., and J.H. Pries. 2000. Constructed wetlands for livestock wastewater management. Ecological Engineering 15: 41-55.

Maine, M.A., N. Suñe, H. Hadad, G. Sánchez, and C. Bonetto. 2009. Influence of vegetation on the removal of heavy metals and nutrients in a constructed wetland. Journal of Environmental Management 90: 355-363.

Melack, J.M., L.L. Hess, M. Gastil, B.R. Forsberg, S.K. Hamilton, I.B.T. Lima, and E.M.L.M. Novo. 2004. Regionalization of methane emissions in the Amazon Basin with microwave remote sensing. Global Change Biology 10: 530-544.

Mitsch, W.J. 1995. Restoration of our lakes and rivers with wetlands – an important application of ecological engineering. Water Science and Technology 31: 167- 177.

Mitsch, W.J. and X. Wu. 1995. Wetlands and global change. In, R. Lal, J. Kimble, E. Levine, and B.A. Stewart (Eds.), Advances in Soil Science, Soil Management and Greenhouse Effect. Lewis Publishers, Boca Raton, FL, USA. pp. 205-230.

Mitsch, W.J. and J.G. Gosselink. 2007. Wetlands, 4th edition. John Wiley & Sons, Inc., New York, NY, USA.

Mitsch, W.J., J.G. Gosselink, C.J. Anderson, and L. Zhang. 2009. Wetland Ecosystems. John Wiley & Sons, Inc., New York, NY, USA.

9

Mitsch, W.J., A.M. Nahlik, P. Wolski, B. Bernal, L. Zhang, and L. Ramberg. in press. Tropical wetlands: Seasonal hydrologic pulsing, carbon sequestration, and methane emissions. Wetlands Ecology and Management.

Moore, T.R. and R. Knowles. 1990. Methane emissions from fen, bog and swamp peatlands in Quebec. Biogeochemistry 11: 45-61.

Moovsavi, S.C., P.M. Crill, E.R. Pullman, D.W. Funk, and K.M. Peterson. 1996.

Controls on CH4 flux from an Alaskan boreal wetland. Global Biogeochemical Cycles 10: 287-296.

Naser, H.M., O. Nagata, S. Tamura, and R. Hatano. 2007. Methane emissions from five paddy fields with different amounts of rice straw application in central Hokkaido, Japan. Soil Science and Plant Nutrition 53: 95-101.

Nzengy’a, D.M. and B.E.L. Wishitemi. 2001. The performance of constructed wetlands for wastewater treatment: a case study of Splash wetland in Nairobi, Kenya. Hydrological Processes 15: 3239-3247.

Postel, S. and S. Carpenter. 1997. Freshwater ecosystem services. In: Daily, G.C. (Ed.), Nature’s Services: Societal Dependence on Natural Ecosystems. Island Press, Washington, DC, USA. pp. 195-214.

Rask, H., J. Schoenau, and D. Anderson. 2002. Factors influencing methane flux form a boreal forest wetland in Saskatchewan, Canada. Soil Biology and Biochemistry 34: 435-443.

Rose, C. and W.G. Crumpton. 2006. Spatial patterns in dissolved oxygen and methane concentrations in a prairie pothole wetland in Iowa, USA. Wetlands 26: 1020- 1025.

Segers, R. 1998. Methane production and methane consumption: a review of processes underlying wetland methane fluxes. Biogeochemistry 41: 23-51.

Shannon, R.D. and J.R. White. 1994. A three-year study of controls on methane emissions from two Michigan peatlands. Biogeochemistry 27: 35-60.

Singh, S., J.S. Singh, and A.K. Kashyap. 1999. Methane flux from irrigated rice fields in relation to crop growth and N-fertilization. Soil Biology and Biochemistry 31: 1219-1228.

Singh, S.N., K. Kulshreshtha, and S. Agnihotri. 2000. Seasonal dynamics of methane emission from wetlands. Chemosphere: Global Change Science 2: 39-46.

10 Smemo, K.A. and J.B. Yavitt. 2006. A multi-year perspective on methane cycling in a shallow peat fen in central New York State, USA. Wetlands 26: 20-29.

Snyder, J.M. 2002. Methane emissions from the tropical Atawapaskat wetlands. Journal of Atawapaskat Research 1: 001-007.

Solano, M.L., P. Soriano, and M.P. Ciria. 2004. Constructed wetlands as a solution for wastewater treatment in small villages. Biosystems Engineering 87: 109-118.

Stone, K.C., M.E. Poach, P.G. Hunt, and G.B. Reddy. 2004. Marsh-pond-marsh constructed wetland design analysis for swine lagoon wastewater treatment. Ecological Engineering 23: 127-133.

Thullen, J.S., J.J. Sartoris, and S.M. Nelson. 2005. Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance. Ecological Engineering 25: 583-593.

Wang, B., H.U. Neue, and H.P. Samonte. 1997. The effect of controlled soil

temperature on diel CH4 emission variation. Chemosphere 35: 2083-2092.

Whalen, S.C. 2005. Biogeochemistry of methane exchange between natural wetlands and the atmosphere. Environmental Engineering Science 22: 73-94.

Whigham, D.F. and T.E. Jordan. 2003. Isolated wetlands and water quality. Wetlands 23: 541-549.

Wilson, J.O., P.M. Crill, K.B. Bartlett, D.I. Sebacher, R.C. Harriss, and R.L. Sass. 1989. Seasonal variation of methane emissions from a temperate swamp. Biogeochemistry 8: 55-71.

Yu, K.W., Z.P. Wang, A. Vermoesen, W.H. Patrick Jr., and O. Van Cleemput. 2001. Nitrous oxide and methane emissions from different soil suspensions: Effect of soil redox status. Biology and Fertility of Soils 34: 25-30.

Yu, K., S.P. Faulkner, and M.J. Baldwin. 2008. Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration. Global Change Biology 14: 798-812.

11

CHAPTER 2: TROPICAL TREATMENT WETLANDS DOMINATED BY FREE-

FLOATING MACROPHYTES FOR WATER QUALITY IMPROVEMENT IN COSTA

RICA1

2.1 Abstract

Five tropical treatment wetlands dominated by floating aquatic plants and constructed to deal with a variety of wastewaters were compared for their effectiveness in treating organic matter and nutrients in the Parismina River Basin in eastern Costa Rica.

Wastewaters were from a dairy farm, a dairy processing plant, a banana paper plant, and a landfill. Four of the five wetland systems were effective in reducing nutrient levels of effluents before water was discharged into rivers. Ammonia levels in water entering most wetlands were considerably higher than ambient (i.e., riverine) levels; concentrations were reduced by as much as 92% in the wetlands and retained at a maximum rate of 166 g N m−2 year−1. Nitrate nitrogen removal was variable, but occurred in low concentrations in the inflows (less than 1 mg N L−1). Phosphate phosphorus was present in high levels but was effectively reduced through the wetlands

(92 and 45% reductions through dairy farm wetlands, 83% reduction through banana paper wetlands, and 80% reduction through dairy processing wetlands). Retention of

1 Nahlik, A.M. and W.J. Mitsch. 2006. Tropical treatment wetlands dominated by free-floating macrophytes for water quality improvement in Costa Rica. Ecological Engineering 28: 246-257. 12 phosphate phosphorus ranged from 0.1 to 10.7 g P m−2 year−1 in the treatment wetlands.

Dissolved oxygen in the wetland outflows were ≤2 mg L−1 in three of the sampled wetlands, most likely a result of the abundant free-floating macrophytes that sheltered the water from diffusion and shaded aquatic productivity. The efficacy of these created wetlands to treat effluents from different sources varied, and modified wetland designs or active management may be necessary to improve water quality even further.

Recommendations on tropical wetland design and management are presented, as are suggestions for implementing this ecological engineering approach with farmers in

Central America.

2.2 Introduction

Costa Rica relies on both eco-tourism and agriculture for a majority of its income.

Deterioration of coastal and inland water quality due to agriculture and small industry threatens the profitability of eco-tourism and has become a large concern to Costa Rica

(Figueres Olsen, 1995). To preserve the environmental integrity of the country, strict water quality regulations have been placed on water that is discharged into local rivers and streams. Although regulations for the treatment of effluents apply to all farms and industries, the added cost of this process may be enough to be detrimental to the existence of small farms and other businesses. Costa Rica’s expected signing of the Central

American Free Trade Agreement (CAFTA) is predicted to have additional negative impacts on the profits of already struggling local farmers and small-industry (Weinberg,

2004), compelling exploration of more economical wastewater systems.

13 Wetlands for waste treatment have been largely investigated in temperate and subtropical zones of North America and Europe, but few studies have documented their effectiveness in tropical regions of the world. Wastewater treatment wetlands can be both a cost-efficient and effective means to improve water quality before effluents are discharged into major rivers (Hammer, 1992; Kadlec and Knight, 1996; Cronk, 1996;

Verhoeven and Mueleman, 1999; Mitsch and Gosselink, 2000; Knight et al., 2000;

Nzengy’a and Wishitemi, 2001; Shutes, 2001; Stone et al., 2004; Mitsch and Jørgensen,

2004). Other economic benefits, such as vegetation for animal feed (e.g., floating aquatic plants) and habitat for harvestable fish (e.g., tilapia), make wetlands an attractive option for meeting water quality standards through nutrient reduction to farmers and small industry (Greenway and Simpson, 1996; Denny, 1997; Costa-Pierce, 1998).

Tropical treatment wetlands, because of the lack of killing winters, are often dominated by floating aquatic plants rather than emergent macrophytes that are more common in temperate regions. Hence, this study will emphasize the functioning of treatment wetlands dominated by floating aquatic plants – notably Pistia stratiotes (water lettuce) and Eichhornia crassipes (water hyacinth) – as the dominant vegetation.

Floating aquatic plant wetlands are described in detail by DeBusk and Reddy (1987),

Brix and Schierup (1989), Reed et al. (1995), and Vymazal et al. (1998), and their major application has been in the tropics and subtropics (Mitsch, 1977; Okurut et al., 1999; Lin et al., 2002).

In this investigation, we examined the efficacy of five created wetland systems dominated by floating aquatic plants in treating four different wastewater sources in eastern Costa Rica: a dairy farm, a dairy processing plant, a banana paper plant, and a

14 landfill. While our study emphasized the changes in water quality as water passed through the wetlands, we also compared the influents and effluents to natural waters in adjacent bodies of water. Recommendations for treatment wetland improvement and construction are made for farmers and industry managers to promote water quality improvement in the Caribbean costal region of Central America.

2.3 Methods

2.3.1 Site description

We measured hydrology, water quality and vegetation structure in five created wetland systems in eastern Costa Rica that treat four different wastewater streams carrying manure, dairy wastewater, paper pulp, and landfill leachate (Table 2.1). For comparison, we also investigated background water quality in five nearby reference bodies of water, which include local rivers, streams, and wetlands (Table 2.2). Treatment wetlands and reference sites were located on the 3300 ha campus of EARTH University, which is located 60 km from the eastern (Caribbean) coast of Limon Province, Costa

Rica, and between the towns of Guacimo (northwest) and Pocora (southeast). EARTH

University and the treatment wetlands used in this study were in the Parismina River watershed (Fig. 2.1), a historically pre-montane wet forest and tropical moist forest dominated landscape. Much of the land, however, has been developed for agriculture

(e.g., banana and pineapple plantations). The 2950 km2 Parismina watershed receives a substantial and consistent amount of rain (EARTH University receives an average of 291 mm month−1) due to its windward location with respect to the volcanic Cordillera Central mountain chain. The underlying geology of the area is made up of quaternary

15 sedimentary and volcanic rocks (Castillo-Muñoz, 1983), influenced by the near-by volcanoes, with poorly drained alluvial soils on flat relief (Vásquez Morera, 1983). The area is susceptible to flooding, and the clayey, hydromorphic soils (Aquepts) support many small riparian wetlands.

The treatment wetland areas ranged from 89 to 1741 m2 and were generally dominated by free-floating macrophytes. Vegetation surveys were conducted in July

2004, just before the beginning of the study by identifying all species present in the wetlands and sketching the relative basin morphology and vegetative groupings within the basin. Routine maintenance (i.e., dredging) was being performed on the second basin of the Planta de Papel wetlands during the vegetation survey; therefore, a survey was not conducted for this wetland. Major modifications to the wetland basins, such as dredging, were not performed once water sampling began.

2.3.2 Wetland morphology and hydrology

Wetland depths were measured at several points throughout the wetlands and averaged to determine mean depth. Inflows to the wetlands were dominated by anthropogenic inputs, with the exception of the Relleno Sanitario wetland. Workers followed a routine schedule for washing and disposal of wastewater, and inflows were consistent from week to week throughout the study. Due to the location of this study, seasonality was minimal and precipitation remained consistent from month to month.

Inflow rates from concentrated sources (e.g., pipes or weirs) were calculated using a timed-volume method, and inflow rates from streams were determined using a float- distance method. If a wetland had more than one major hydrologic source (e.g., an

16 effluent input and natural stream), both inflow rates were measured and added to obtain gross inflow. Four wetland basins received multiple inflows: Lecheria 1, Lecheria 3,

LaPA, and Planta de Papel wetlands.

2.3.3 Wastewater characterization

Wastewater effluents entering the wetlands were different from site to site (Table

2.1). The Lecheria wetlands received wash water laden with manure from a small animal facility housing pigs. Water entering the LaPA wetland was concentrated whey, high in lipids and other by-products resulting from yogurt, cheese, and milk production. The

Planta de Papel wetland received a fibrous effluent from a factory that produced paper from banana plant material. Water entering the Relleno Sanitario wetland was primarily rainwater that passed through a landfill, which was active from 1991 to 2000.

2.3.4 Water sampling and analysis

Water samples were collected for both treatment wetlands and reference sites during five sampling periods from August 2004 to March 2005. Upon collection of a sample, pH, water temperature, conductivity, oxidation–reduction potential (ORP), and dissolved oxygen (DO) were measured in the field with a YSI 556 Multi Probe System.

Collected samples were stored on ice in the field and immediately refrigerated at 5 °C upon reaching the lab on EARTH University’s campus where additional analyses were performed. Half of each sample was filtered in the laboratory using Whatman Grade 540

(8 µm) filter paper and stored in a separate bottle until nutrient analysis. Unfiltered

17 samples were used for determining oxygen-demanding substances and suspended materials. All analyses were completed within 28 days from the date of collection.

Analyses for oxygen-demanding substances, suspended materials, and nutrients were completed in a lab. Analysis for biochemical oxygen demand (BOD) began within

24h of sample collection using the 5-day BOD test (APHA, 1998). Chemical oxygen demand (COD) was analyzed using the closed reflux, colorimetric method with Hach premixed reagents in digestion tubes and measured for absorbance on a Hach DR/870

Portable Colorimeter. Turbidity was measured with a Hach 2100N Turbidimeter using nephelmetric methods. Nutrient analyses were performed using the phenate method for

ammonia (NH4–N), the ultraviolet spectrophotometric screening method for nitrate

(NO3–N), and the stannous chloride method for phosphates (PO4–P). After color development, samples were read on a Therm Spectronic Heλios spectrophotometer for colorimetric absorbance. Standard curves were made for each set of samples analyzed using colorimetric methods.

Laboratory analysis quality and objectivity were assured by assigning identification numbers to each sample and analyzing them unassociated with the site from which they were collected. Samples of deionized water (i.e., blanks) were also added randomly into the sampling regime to serve as quality checks. Duplicate samples were collected from every site and run separately to verify analysis accuracy.

2.3.5 Statistical analysis

Chemical concentrations were flow-weighted for wetlands with multiple inflows.

Statistical analyses were conducted in Microsoft Excel and SPSS. Because the data were

18 not normally distributed, inflow to outflow values in each of the treatment wetlands were compared using Mann–Whitney tests. Significant differences indicate p ≤ 0.10. Values are specified at p ≤ 0.05 and ≤ 0.01.

2.4 Results

2.4.1 Wetland morphology and hydrology

The five treatment wetlands represented a range of areas and volumes, from 89 m2 and 36 m3 (Relleno Sanitario wetland) to 1340 m2 and 5092 m3 (Lecheria 3-4) (Table

2.1). Average wetland basin area and volume were 961 m2 and 2027 m3, respectively.

Lecheria 1-2, Lecheria 3-4, and Planta de Papel wetlands, had areas near or over 1000 m2 and volumes over 1000 m3 due to their duel basin system (1741, 1340, 985 m2 and 3308,

5092, 1182 m3, respectively), while single basin systems, LaPAand Relleno

Sanitario,weremuch smaller (649, 89 m2 and 519, 36 m3, respectively). Mean depths were similar for most wetlands and averaged 1.6 m (1.1 m without Lecheria 3-4 wetlands). Lecheria 3-4 wetlands were exceptionally deep with a mean depth of 3.8 m

(Table 2.1).

Inflow rates were relatively comparable among most wetlands (40–55 m3 day−1), except for Lecheria 3-4 and LaPA wetlands, which had higher inflow rates due to natural stream inputs in addition to effluent inflows. Despite similar inflow rates, the hydraulic loading rates (HLR) and hydraulic retention times (HRT) varied greatly between wetland systems. Lecheria 1-2, Lecheria 3-4, and Planta de Papel wetlands had noticeably lower

HLR (22, 98, and 28 cm week−1, respectively) and higher HRT (60, 27, and 30 days, respectively) due to their duel basin systems and larger areas (Table 2.1).

19

2.4.2 Wetland vegetation

A total of seven species were found in the treatment wetlands, including P. stratiotes L. (water lettuce), E. crassipes Mart. (water hyacinth), Ipomoea aquatica

Forsskal. (swamp morning-glory), Paspalum repens Bergius. (water paspalum), Azolla microphylla Kaulf. (Mexican mosquito fern), Salvinia minima Baker (water spangles), and Lemna minor L. (lesser duckweed). All wetland systems in this study hosted P. stratiotes and E. crassipes, the two most abundant species observed in this study. I. aquatica and P. repens were also present in considerable numbers in some of the wetlands. Three other species, A. microphylla, S. minima, and Lemna were less common

(Fig. 2.2).

Vegetation maps in Fig. 2.2 generally did not reflect large areas of open water with the exception of the Relleno Sanitario. The maps were created long after harvesting, and floating aquatics had sufficient time to re-colonize open water. Vegetation harvesting at 2–3-month intervals was practiced at every wetland throughout the study period; however, only portions of the wetlands were harvested (generally less than 30% of the entire area). Sampling and harvesting were staggered to minimize the immediate effects of harvesting on water quality, and it was noted that regardless of the wetland, soon after harvesting, Pistia repens and E. crassipes readily re-colonized in a matter of days. Over the time of this study, as different areas of the wetlands were harvested, they became more and more dominated by these two early colonizers.

20 2.4.3 Water quality

A total of 75 water samples were collected and analyzed during the five sampling periods. pH and water temperature were consistent from wetland to wetland with means for all treatment wetland outflows of 6.30 ± 0.04 and 25.44 ± 0.20 ºC for pH and water temperature, respectively (n = 53). Conductivity was low in all wetlands and ranged from

0.07 ± 70 µS cm−1 (Relleno Sanitario wetland) to 0.75 ± 0.29 µS cm−1 (Lecheria 1-2 wetlands). Oxidation–reduction potential was relatively consistent and ranged from −147

± 30 mV (Lecheria 1-2 wetlands) to +101 ± 36 mV (Relleno Sanitario wetland).

2.4.3.1 Oxygen-demanding substances – BOD was not high relative to domestic wastewater in many of the inflows of the treatment wetlands, including Lecheria 3-4 (9

−1 −1 −1 mg O2 L ), LaPA (16 mg O2 L ), Planta de Papel (16 mg O2 L ), and Relleno Sanitario

−1 (10 mg O2 L ; Fig. 2.3a). Significant reductions in BOD took place only in Lecheria 1-2

−1 wetlands (p = 0.095); however, ambient levels of BOD (6–12 mg O2 L ) were reached in the outflows of all wetlands, despite a 17% increase in BOD from inflow to outflow in the Relleno Sanitario wetland (Table 2.3). Removal rates of BOD were especially high in

−2 −1 the Lecheria 1-2, LaPA, and Planta de Papelwetlands (357, 1234, and 81 g O2 m year , respectively; Table 2.4).

As expected, COD was generally higher than BOD in the inflow and outflows of both the reference and treatment sites (Fig. 2.2b). Highest inflow COD occurred in the

−1 −1 Lecheria 1-2 (436 mg O2 L ) and Planta de Papel wetlands (62 mg O2 L ). Significant reductions took place in the Lecheria 1-2 wetlands (93% reduction; p = 0.046). The

Relleno Sanitario wetland increased in COD from inflow to outflow by 27% (Table 2.3). 21 Like BOD, the Lecheria 1-2, LaPA, and Planta de Papel wetlands also had high removal

−2 −1 rates for COD (4650, 808, and 845 g O2 m year , respectively; Table 2.4).

2.4.3.2 Dissolved oxygen – Dissolved oxygen (DO) levels were very low in some of the treatment wetlands, especially in the outflows of the Lecheria 1-2, Lecheria 3-4, and Planta de Papel wetlands (Fig. 2.4). Reference sites tended to have higher DO levels than treatment wetlands because there was water constantly moving at a substantial velocity in most of those systems. The Natural Wetland reference site had lower DO levels than the rest of the reference sites because of the inherent characteristic of a wetland to often have low-oxygen or anaerobic waters. DO increased from inflow to outflow in some of the wetlands with open water, including the LaPA wetland (by 41%) and Relleno Sanitario wetland (by 5%) (Table 2.3). Significant decreases in DO, however, were evident in those wetlands that were completely covered by floating aquatic plants, Lecheria 1-2, Lecheria 3-4, and Planta de Papel wetlands (p = 0.034,

0.021, and 0.034, respectively).

2.4.3.3 Suspended material – Turbidity, as our measure of suspended materials in the water, was relatively low in both reference sites and treatment wetlands, despite treatment wetland inflow turbidities that were higher than ambient conditions (Fig. 2.5).

Significant reductions from inflow to outflow took place in the Lecheria 1-2 wetland (p =

0.034), although large reductions took place in the LaPA, Planta de Papel, and Relleno

Sanitario wetlands as well (60%; Table 2.3). Ambient turbidity levels were not reached in any of the Lecheria wetlands, although levels were relatively low (10–25 NTU).

22 Increases in turbidity were seen in the Lecheria 3-4, but the resulting outflow turbidity of

10 NTU is so low that even the 51% increase from inflow to outflow is probably not a significant reduction in water quality (Table 2.3).

2.4.3.4 Nutrients – Ammonia was in high concentrations in the inflow of the

Lecheria 1-2 wetland, which received concentrated manure effluents (15.8 mg N L−1); however, concentrations were effectively reduced to ambient conditions in the Lecheria

1-2 wetland and most of the other treatment wetlands (Fig. 2.6a). Significant reduction in ammonia concentrations from the inflow to outflow took place in Lecheria 1-2 wetlands

(p = 0.077), although ammonia levels were comparable to ambient levels in Lecheria 3-4 and LaPA wetlands. Ammonia removal rates were low in all treatment wetlands except for Lecheria 1-2 site, most likely due to the high concentration, and thus higher load, of ammonia in the inflow (Table 2.4). Concentrations increased by 123% in the Lecheria 3-

4 wetlands, 136% inthe LaPA wetland, and 80% in the Relleno Sanitario wetland (Table

2.3).

Nitrate concentrations were less than 1mg N L−1 in all reference sites and treatment inflows and outflows (Fig. 2.6b). The highest nitrate concentrations were found in the Wash Water Channel and Mercedes Creek reference sites (0.63 and 0.23 mg

N L−1, respectively) and the inflow to the Planta de Papel wetlands (0.23 mg N L−1).

Nitrate concentrations were significantly reduced in the Planta de Papel wetlands (p =

0.032), although there was some nitrate removal in the LaPA wetland. There were increases in nitrate concentrations in the Lecheria 1-2, Lecheria 3-4, and Relleno

Sanitario wetlands (207, 77, and 78%, respectively; Table 2.3), although outflow

23 conditions were still comparable to those in reference sites. Positive nitrate retention occurred in the LaPA and the Planta de Papel wetlands (10.4 and 2.8 g N m−2 year−1, respectively; Table 2.4).

Phosphate concentrations were low (8–505 µg P L−1) in the reference sites and treatment wetlands (note the scale in Fig. 2.6c). Reductions in phosphate concentrations took place in all wetlands, and significant reductions occurred in Lecheria 1-2 wetlands

(p = 0.034); Table 2.4. Only minimal reductions in phosphate took place in the Relleno

Sanitario wetland (5% reduction) (Table 2.3).

2.5 Discussion

2.5.1 Water quality improvement by tropical treatment wetlands

Most of the wetlands in this study were effective in reducing nutrients. The tropical location of these treatment wetlands provided optimal temperatures for microbial action and nutrient assimilation via plants (Gambrell and Patrick, 1978; Gearhart et al.,

1989), and it is likely to have aided in the high nutrient reductions observed during this study. Ammonia was only detrimentally high in the inflow to the Lecheria 1-2 wetland and was effectively reduced there. Outflow concentrations of ammonia were still higher than ambient conditions in the Relleno Sanitario wetland. Although nitrate and phosphate concentrations were low and did not appear to present problems to downstream ecosystems, Relleno Sanitario wetland had the highest nitrate concentrations in the outflow.

Oxygen-demanding substances (BOD and COD) were not as effectively removed as were nutrients in most of the wetlands. BOD was only reduced in three of the

24 treatment wetlands. Lecheria 1-2 was the only site to significantly reduce BOD, while

BOD increased in the outflows of Lecheria 3-4 and Relleno Sanitario wetlands. COD generally decreased more in the treatment wetlands than did BOD, although COD values were often an order of magnitude higher than BOD. Because COD generally includes

BOD plus other oxygen-demanding processes, the more significant reductions in COD suggest significant decreases in total nitrogen (specifically ammonia), organic compounds, and other oxygen-demanding pollutants.

2.5.2 Hydraulic loading and nutrient retention rates

The Relleno Sanitario wetland appears to be contributing only minimum, if any, improvement to water quality. The small size of this wetland (89 m2) limits its ability to effectively hold large volumes of water and treat concentrated effluents. The hydraulic retention time of the Relleno Sanitario wetland was among the lowest in this study and may contribute to its ineffectiveness to meet reference conditions in the outflows. A larger wetland area would have the potential to support larger communities of plants, and, therefore, better reduce nutrient concentrations and oxygen-demanding substances from the landfill leachate that this small wetland is intended to treat.

There is a distinct pattern in nutrient (ammonia, nitrate, phosphate) and oxygen- demanding substance (BOD, COD) retention for different hydraulic loading rates in the surface flow wetlands used in this study (Fig. 2.7). Nutrient and oxygen demanding substance retention is most effective in those wetlands with low (0–100 cm week−1) and high (>350 cm week−1) hydraulic loading rates. Capacity for retention may be maximized under low hydraulic loading (and hence long retention time) as a result of

25 lengthened exposure of water to microbial processes. Dierberg et al. (2005) demonstrated that phosphorus removal was higher in wetlands with longer hydraulic retention periods, while Diemont (2006) reported similar patterns for total phosphorus and BOD removal in tropical treatment systems in Honduras. Although retention time is generally lower under high hydraulic loading rates, dissolved oxygen is higher (perhaps as a result of water movement and churning) allowing for creation of aerobic conditions and reduction in pollutants like organic matter and ammonia.

Rates of phosphorus removal for wetlands, estimated as only the soluble reactive form of phosphorus in this study, were comparable to those determined in other temperate and subtropical studies. Highest mean phosphate phosphorus retention was

10.4 g P m−2 year−1 for wetlands in this study, and the wetlands, on average, retained 3.5 g

P m−2 year−1. Other studies reported total phosphorus retentions between 0.4 and 45 g P m−2 year−1 (Knight, 1990; Kadlec and Knight, 1996; Mitsch et al., 2000). Mitsch et al.

(2000) report a sustainable retention rate of 1–5 g P m−2 year−1 for treatment wetlands in temperate zones. The treatment wetlands in this study appear to have retained phosphate phosphorus (total phosphorus was not measured in this study) near a sustainable rate, according to that range, although it is conceivable that tropical systems could be more effective than the temperate zone estimates reported above. One of the few recent tropical/subtropical studies reported considerably lower phosphorus retention compared to this study; total phosphorus uptake of experimental mesocosm-scale wetlands in

Florida was only 0.32 g P m−2 year−1 (DeBusk et al., 2004).

Nitrate–nitrogen retention was lower in this study than other comparable wetland studies such as those conducted in southern California, which report nitrogen retention

26 between 100 and 200 g N m−2 year−1 (Bachand and Horne, 2000; Reilly et al., 2000;

Sartoris et al., 2000). Mitsch et al. (2000) suggested a sustainable nitrate retention range of 10–40 g N m−2 year−1 for wetland in temperate zones, and a higher rate in warmer climates. Some of the wetlands in our study were not effectively retaining nitrate– nitrogen; on average, there was a net export of nitrate–nitrogen for all wetlands in this study (2.7 g N m−2 year−1). One explanation for ineffective nitrate retention in some wetlands is high ammonia retention (mean of 165 g N m−2 year−1) in those wetlands that had low nitrate–nitrogen retention. Even those wetlands that were retaining nitrate– nitrogen were not reaching potential sustainable levels; the Planta de Papel and the LaPA wetlands retained relatively low amounts of nitrate–nitrogen (2.8 and 10.4 g N m−2 year−1, respectively).

2.5.3 Free-floating macrophytes

Free-floating macrophytes, especially P. stratiotes (water lettuce) and E. crassipes

(water hyacinth), dominated these tropical ecosystems to such an extent that without regular maintenance through plant harvesting, there would have been no open water in any of the wetlands studied here. This is quite different than in typical treatment wetlands in temperate climates that are usually designed to support emergent macrophytes (Kadlec and Knight, 1996; Mitsch and Jørgensen, 2004). The abundance of these free-floating plants causes both positive and negative ecosystem habitat and water quality patterns. On the negative side, the plants prohibited submersed photosynthesis and exchange between the atmosphere and water column, resulting in low dissolved oxygen levels in the water and hence less than optimum retention of oxygen demanding

27 substances. On the positive side, free-floating macrophytes provide shading of the water column, thereby providing a cooler habitat for fish and macroinvertebrates in what otherwise would be a warm water tropical environment. Despite floating aquatic plants providing cooler water temperatures and abundant food sources that help create optimal habitat structure for fish and invertebrates, it has been reported that wetlands with floating aquatics support larger mosquito larvae populations than do open water areas due to reduced dissolved oxygen concentrations (Greenway et al., 2003). Few mosquitoes were observed in the wetlands during this study, with the exception of the Relleno

Sanitario, the shallowest wetland. This concurs with several other studies that report that deep-water wetlands (>0.2–0.6 m) supported less mosquito larvae compared to shallow- water wetlands (Walton and Workman, 1998; Thullen et al., 2002; Diemont, 2006).

Deep-water wetlands also provide habitat for fish that commonly occur, such as tilapia, which can be harvested as a salable product, thus potentially increasing the economic efficiency of these tropical treatment wetlands.

Most importantly, the floating aquatic plants aid in nutrient removal. For example, the low dissolved oxygen prevented increases in nitrate–nitrogen that otherwise would occur through nitrification of the high concentrations of ammonia found in several of the wetlands and increased potential for denitrification. Past studies have demonstrated that both submerged and free-floating macrophytes have a high capacity to remove large concentrations of nutrients (Greenway, 1997; Sooknah and Wilkie, 2004).

Under high temperature conditions, E. crassipes (water hyacinth) has been reported to assimilate up to 777 mg N m−2 day−1 and 200 mg P m−2 day−1 (DeBusk et al., 1995).

These high assimilation rates have been partially attributed to the high growth rates of

28 these specific plants and are much higher on an annual basis than nutrient retention rates experienced in emergent macrophyte, e.g., Typha, water quality wetlands in temperate climates. The roots of floating aquatic plants, such as those found in the wetlands in

Costa Rica, provide substrate to microbial communities and aerobic microsites in a generally anaerobic environment (Ma and Yan, 1989). Microbial communities promote nutrient assimilation by plant roots and largely aid in chemical transformations, including nitrification and denitrification (Peterson and Teal, 1996; Drenner et al., 1997; Todd et al., 2003). In addition, the plants serve as a secondary carbon source as they decompose, an important component to nitrate–nitrogen removal via denitrification (Hamersley et al.,

2001). Finally, the floating aquatic plants reduce the amount of sediments that accumulates within the system by retaining biosolids within the root mass, which are then removed by snail and macroinvertebrate grazing or by purposeful aquatic plant harvesting by humans (Billore et al., 1998; Austin, 2000).

2.5.4 Management and design considerations

Macrophyte harvesting is both necessary to maintain open water areas (allowing for increased oxygen exchange) and can be beneficial to farmers as mulch or animal feed.

Frequent plant harvesting can also be beneficial to wetland function by maximizing nutrient retention through removal of nutrient laden plants. Additionally, Greenway et al.

(2003) recommend a minimum of 30% open water to allow for sufficient conditions for mosquito predation. Free-floating aquatic plants in several of the wetlands in this study were harvested as frequently as monthly by campus maintenance workers. At no time were 100% of the plants of a wetland harvested; generally less than 30% of the

29 macrophytes were harvested at one time, allowing rapid re-growth. Nonetheless, the intense management of the treatment wetlands, including macrophyte harvesting and dredging, has altered the natural development of these ecosystems. Harvesting practices especially seemed to have the effect of “restarting” the wetland into an earlier stage of succession by creating open water areas that could be quickly dominated by early colonizers, such as P. stratiotes and E. crassipes. Despite the many benefits plant harvesting has on wetland function, this practice may also result in a less predictable habitat for aquatic organisms and microbial communities in the root community.

Additional studies are needed to better understand the effect of plant harvesting on wetland succession and development.

Removal of macrophytes can result in improved water quality; however, the plant material harvested from the wetlands in this study was usually deposited adjacent to the wetlands, thereby allowing nutrients to return to the wetland once plants decomposed. A more effective harvesting protocol might include moving the harvested material to agricultural fields as fertilizer or immediately using the harvested material as animal feed.

In addition, workers expended much energy manually harvesting, with no insight of how the harvest frequency and amount harvested affected nutrient removal (the primary function of the treatment wetlands). Future studies that focus on optimal harvesting regimes, especially for maximizing nutrient assimilation, are needed.

Management practices of the treatment wetlands in this study also included occasional dredging to maintain high water capacities. Steep banks and uniform depths were observed in most of the treatment wetland basins as a result from basin modification. These homogeneous basins are not conducive to a diverse assemblage of

30 plants, diverse habitat structure, or healthy aquatic life. Dredging is generally a destructive process, and although the wetlands in this study receive relatively turbid water, indicating high sediment loads, dredging does not seem to be warranted. Long- term processes, such as nutrient removal through sedimentation and storage, are compromised by the short-term benefits of dredging (i.e., higher water storage capacity).

Nutrient removal might be further improved by providing additional habitat in the form of contours, hummocks, and graded banks for a high diversity of species that would assimilate nutrients from both the water column and the sediment (Greenway, 2005;

Thullen et al., 2005).

2.5.5 Using treatment wetlands in tropical regions

Treatment wetlands, such as those used for a variety of wastewater streams on this tropical university campus in Costa Rica, have the potential to provide an ecological solution to increasing water pollution problems caused by nonpoint and point sources related to more intensive agricultural practices being implemented in Central America, partially as a result of the Central American Free Trade Agreement. It is recommended that caution be taken when constructing treatment wetlands so that favorable conditions for the proliferation of mosquitoes are not met; wetlands should have consistent flow, a minimum of 30% open water (Greenway et al., 2003), and should be greater than 0.2–0.6 m in depth (Walton and Workman, 1998; Thullen et al., 2002; Diemont, 2006). The treatment wetland alternative also provides a relatively inexpensive approach for small- scale farmers to continue to operate in the face of appropriately stronger water quality standards. These water quality standards are vital for the economy of countries such as

31 Costa Rica that depend heavily on eco-tourism. The high water quality in streams and rivers throughout Costa Rica are attractors for a high number of river rafters and others who appreciate the clean water. There is also increased concern of deteriorating water quality and coral reef stress in coastal waters in the Caribbean that receive surface water from river systems such as the Parismina River. Although nitrogen effluents have not been identified yet to be a significant concern for coastal waters, increased agricultural intensity in the uplands will make sediments and nitrogen significant targets for water quality improvement.

2.6 Acknowledgments

The authors would like to acknowledge the partnership with EARTH University,

Costa Rica, and Jay Martin and Stephanie Lansing for their invaluable help in the field and lab. Significant contributions were made by Bert Kolhmann, Marlon Breve, Julio

Tejada, Heide Stein, Danny Vasquez, Maria Muñoz, Wilmer Romero, Angelica Cocha,

Osman Echeverria, and el laboratorio de aguas y suelos staff (Herbert Arrieta, director) in

Costa Rica and Li Zhang and Blanca Bernal-Martinez at the Olentangy River Wetland

Research Park in USA. Special thanks for organizing and supporting this research to

Jane Yeomans, Carlos Hernandez, Dave Hansen, and Richard Fortner. Funding for this project was provided by United States Department of Energy (EARTH University/OSU

Program on Collaborative Environmental Research in the Humid Tropics). Olentangy

River Wetland Research Park publication number 06-007.

32 2.7 References

American Public Health Association, American Water Works Association, Water Environment Federation, 1998. Standard Methods for the Examination of Water and Wastewater, 20th ed. United Book Press, Inc., Baltimore, MD.

Austin, D., 2000. Final Report on the South Burlington, Vermont: Advanced Ecologically Engineered System (AEES) for Wastewater Treatment. Report to the Massachusetts Foundation for Excellence in Marine and Polymer Science, Inc.

Bachand, P.A.M., Horne, A.J., 2000. Denitrification in constructed free-water surface wetlands. I. Effects of vegetation and temperature. Ecol. Eng. 14, 17–32.

Billore, S.K., Bharadia, R., Kumar, A., 1998. Potential removal of particulate matter and nitrogen through roots of water hyacinth in a tropical natural wetland. Curr. Sci. 74, 154–156.

Brix, H., Schierup, H.H., 1989. The use of aquatic macrophytes in water-pollution control. Ambio 18, 100–107.

Castillo-Muñoz, R., 1983. Geology. In: Janzen, D.H. (Ed.), Costa Rican Natural History. The University of Chicago Press, Chicago, pp. 47–62.

Costa-Pierce, B.A., 1998. Preliminary investigation of an integrated aquaculture-wetland ecosystem using tertiary-treated municipal wastewater in Los Angeles County, California. Ecol. Eng. 10, 341–354.

Cronk, J.K., 1996. Constructed wetlands to treat wastewater from dairy and swine operations: a review. Agric. Ecosyst. Environ. 58, 97–114.

DeBusk, T.A., Reddy, K.R., 1987. Wastewater treatment using floating aquatic macrophytes; contaminant removal processes and management strategies. In: Reddy, K.R., Smith, W.H. (Eds.), Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing, Inc., Orlando, FL, pp. 643–656.

DeBusk, T.A., Peterson, J.E., Reddy, K.R., 1995. Use of aquatic and terrestrial plants for removing phosphorus from dairy wastewaters. Ecol. Eng. 5, 371–390.

DeBusk, T.A., Grace, K.A., Dierberg, F.E., Jackson, S.D., Chimney, M.J., Gu, B., 2004. An investigation of the limits of phosphorus removal in wetlands: a mesocosm study of a shallow periphyton-dominated treatment system. Ecol. Eng. 23, 1–14.

Denny, P., 1997. Implementation of constructed wetlands in developing countries. Water Sci. Technol. 35, 27–34.

33 Diemont, S.A.W., 2006. Mosquito larvae density and pollutant removal in tropical wetland treatment systems in Honduras. Environ. Int. 32, 332–341.

Dierberg, F.E., Juston, J.J., DeBusk, T.A., Pietro, K., Gu, B., 2005. Relationship between hydraulic efficiency and phosphorus removal in a submerged aquatic vegetation- dominated treatment wetland. Ecol. Eng. 25, 9–23.

Drenner, R.W., Day, D.J., Basham, S.J., Smith, J.D., Jensen, S.I., 1997. Ecological water treatment system for removal of phosphorus and nitrogen from polluted water. Ecol. Appl. 7, 381–390.

Figueres Olsen, J.M., 1995. Sustainable development: a challenge for Costa Rica. SAIS Rev. 16, 187–202.

Gambrell, R.P., Patrick Jr., W.H., 1978. Chemical and microbiological properties of anaerobic soils and sediments. In: Hook, D.D., Crawford, R.M. (Eds.), Plant Life in Anaerobic Environments. Ann Arbor Science Publishers, Ann Arbor, MI, pp. 375–423.

Gearhart, R.A., Klopp, F., Allen, G., 1989. Constructed free surface wetland to treat and receive wastewater; pilot project to full scale. In: Hammer, D.A. (Ed.), Constructed Wetlands for Wastewater Treatment. Lewis Publishers, Chelsea, MI, pp. 121–138.

Greenway, M., 1997. Nutrient content of wetland plants in constructed wetland receiving municipal effluent in tropical Australia. Water Sci. Technol. 35, 135–142.

Greenway, M., 2005. The role of constructed wetlands in secondary effluent treatment and water reuse in subtropical and arid Australia. Ecol. Eng. 25, 501–509.

Greenway, M., Simpson, J.S., 1996. Artificial wetlands for wastewater treatment, water reuse and wildlife in Queensland, Australia. Water Sci. Technol. 33, 221–229.

Greenway, M., Dale, P., Chapman, H., 2003. An assessment of mosquito breeding and control in four surface flow wetlands in tropical–subtropical Australia. Water Sci. Technol. 48, 121–128.

Hammer, D.A., 1992. Designing constructed wetland systems to treat agricultural non- point source pollution. Ecol. Eng. 1, 49–82.

Hamersley, M.R., Howes, B.L., White, D.S., Johnke, S., Young, D., Peterson, S.B., Teal, J.M., 2001. Nitrogen balance and cycling in an ecologically engineered septage treatment system. Ecol. Eng. 18, 61–75.

34 Kadlec, R.H., Knight, R.L., 1996. Treatment Wetlands. Lewis Publishers, Boca Raton, FL.

Knight, R.L., 1990. Wetland systems. In: Natural Systems for Wastewater Treatment. Manual of Practice FD-16. Water Pollution Control Federation, Alexandria, VA, pp. 211–260.

Knight, R.L., Payne, V.W.E., Borer, R.E., Clarke Jr., R.A., Pries, J.H., 2000. Constructed wetlands for livestock wastewater management. Ecol. Eng. 15, 41–55.

Lin, Y., Jing, S., Wang, T., Lee, D., 2002. Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands. Environ. Pollut. 119, 413–420.

Ma, S., Yan, J., 1989. Ecological engineering for treatment and utilization of wastewater. In: Mitsch, W.J., Jørgensen, S.E. (Eds.), Ecological Engineering, An Introduction to Ecotechnology. JohnWiley & Sons, Inc., New York, pp. 185–217.

Mitsch, W.J., 1977. Water hyacinth (Eichhornia crassipes) nutrient uptake and metabolism in a north-central Florida marsh. Arch. Hydrobiol. 81, 188–210.

Mitsch, W.J., Gosselink, J.G., 2000. Wetlands, third ed. John Wiley & Sons, Inc., New York.

Mitsch, W.J., Horne, A.J., Nairn, R.W., 2000. Nitrogen and phosphorus retention in wetlands—ecological approaches to solving excess nutrient problems. Ecol. Eng. 14, 1–7.

Mitsch, W.J., Jørgensen, S.E., 2004. Ecological Engineering and Ecosystem Restoration. John Wiley & Sons, Inc., Hoboken, NJ.

Nzengy’a, D.M., Wishitemi, B.E.L., 2001. The performance of constructed wetlands for wastewater treatment: a case study of Splash wetland in Nairobi, Kenya. Hydrol. Process 15, 3239–3247.

Okurut, T.O., Rijs, G.B.J., van Bruggen, J.J.A., 1999. Design and performance of experimental constructed wetlands in Uganda, planted with Cyperus papyrus and Phragmites mauritianus. Water Sci. Technol. 40, 265–271.

Peterson, S.B., Teal, J.M., 1996. The role of plants in ecologically engineered wastewater treatment systems. Ecol. Eng. 6, 137–148.

Reed, S.C., Crites, R.W., Middlebrooks, E.J., 1995. Natural Systems for Waste Management and Treatment, second ed. McGraw-Hill, New York.

35 Reilly, J.F., Horne, A.J., Miller, C.D., 2000. Nitrate removal from a drinking water supply with large free-surface constructed wetlands prior to groundwater recharge. Ecol. Eng. 14, 33–47.

Sartoris, J.J., Thullen, J.S., Barber, L.B., Salas, D.E., 2000. Investigation of nitrogen transformations in a southern California constructed wastewater treatment wetland. Ecol. Eng. 14, 49–65.

Shutes, R.B.E., 2001. Artificial wetlands and water quality improvement. Environ. Int. 26, 441–447.

Sooknah, R.D., Wilkie, A.C., 2004. Nutrient removal by floating aquatic macrophytes cultured in anaerobically flushed dairy manure wastewater. Ecol. Eng. 22, 27–42.

Stein, H., Springer, M., Kohlmann, B. Comparison of two sampling methods for biomonitoring using aquatic macroinvertebrates in the Dos Novillos River, Costa Rica. Ecol. Eng., in press.

Stone, K.C., Poach, M.E., Hunt, P.G., Reddy, G.B., 2004. Marsh-pond-marsh constructed wetland design analysis for swine lagoon wastewater treatment. Ecol. Eng. 23, 127–133.

Thullen, J.S., Sartoris, J.J., Walton, W.E., 2002. Effects of vegetation management in constructed wetland treatment cells on water quality and mosquito production. Ecol. Eng. 18, 441–457.

Thullen, J.S., Sartoris, J.J., Melson, S.M., 2005. Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance. Ecol. Eng. 25, 583–593.

Todd, J., Brown, E.J.G., Wells, E., 2003. Ecological design applied. Ecol. Eng. 20, 412– 440.

Vásquez Morera, A., 1983. Soils. In: Janzen, D.H. (Ed.), Costa Rican Natural History. The University of Chicago Press, Chicago, USA, pp. 63–65.

Verhoeven, J.T.A., Mueleman, A.F.M., 1999. Wetlands for wastewater treatment: opportunities and limitations. Ecol. Eng. 12, 5–12.

Vymazal, J., Brix, H., Cooper, P.F., Haberl, R., Perfler, R., Laber, J., 1998. Removal mechanisms and types of constructed wetlands. In: Vymazal, J., Brix, H., Cooper, P.F., Green, M.B., Haberl, R. (Eds.), Constructed Wetlands for Wastewater Treatment in Europe. Backhuys Publishers, Leiden, The Netherlands, pp. 17–66.

36 Walton, W.E., Workman, P.D., 1998. Effect of marsh design on the abundance of mosquitoes in experimental constructed wetlands in southern California. J. Am. Mosq. Control Assoc. 14, 95–107.

Weinberg, S., 2004. The Central America Free Trade Agreement: Three Reasons for Congress to Vote No, Comments to a Congressional Briefing on CAFTA, Oxfam America Policy Advisor, January 22, 2004.

37

Table 2.1. Morphology and hydrology of wetland systems in this study.

38

Table 2.2. Condition and description of reference sites used in this study.

NH4-N NO3-N PO4-P BOD COD Dissolved Oxygen Turbidity

Wetland % Reduction % Reduction % Reduction % Reduction % Reduction % Increase % Reduction

Lecheria 1-2 92 (0.042) -207 (0.946) 92 (0.011) 83 (0.057) 93 (0.213) -84 (0.043) 70 (0.063)

Lecheria 3-4 -123 (0.770) -77 (0.542) 45 (0.166) -40 (0.579) 28 (0.213) -93 (0.003) -51 (0.766)

LaPA -136 (0.481) 89 (0.022) 80 (0.083) 37 (0.077) 41 (0.424) 27 (0.050) 43 (0.024)

Planta de Papel 38 (0.275) 84 (0.013) 83 (0.244) 36 (0.379) 95 (0.389) -79 (0.000) 78 (0.371)

Relleno Sanitario -80 (0.609) -78 (0.619) 5 (0.969) -17 (0.817) -27 (0.877) 5 (0.0872) 48 (0.416)

Bold negative numbers emphasize net decrease of water quality.

39

Table 2.3. Percent change by concentration and mass (all reductions, except dissolved oxygen) of water quality indicators in the wetlands used in this study. Numbers in parentheses represent the associated p-value for the reduction from inflow to outflow.

40

Table 2.4. Rates of nutrient and oxygen-demanding substance inflow, outflow, and removal (g m-2 year-1) in the treatment wetlands.

Figure 2.1. Hydrologic map of the study area, EARTH University, located in Limon Province, eastern Costa Rica. Numbers represent the following sampling sites: (1) Lecheria wetlands, (2) LaPA wetland, (3) Planta de Papel wetland, (4) Relleno Sanitario wetland, (5) Empacadora Bananos, and (6) Dos Novillos River. Black areas represent neighboring countries (Nicaragua to the north and Panama to the south), and shaded area within Costa Rica represents Limon Province.

41

Figure 2.2. General morphology and vegetation cover of: (a) Lecheria 1-2 wetlands, (b) Lecheria 3-4 wetlands, (c) LaPA wetland, (d) Planta de Papel wetland, and (e) Relleno Sanitario wetland. Vegetation surveys were conducted in August 2004, at the beginning of the study. Routine maintenance (i.e., dredging) was being performed on the second basin of the Planta de Papel wetlands during the survey; therefore, a survey was not conducted for this wetland. Vegetation is listed in order of most dominant to least common. Wetlands are orientated so inflows are on the top and outflows are on the bottom.

42

−1 Figure 2.3. Oxygen-demanding substances (mg O2 L ), including: (a) biochemical oxygen demand and (b) chemical oxygen demand in inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows.

43

Figure 2.4. Dissolved oxygen concentrations (mg L−1) in inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows.

44

Figure 2.5. Turbidity (NTU) of inflows (dark gray bars) and outflows (light gray bars) of treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows.

45

Figure 2.6. Nutrient concentrations, including: (a) ammonia–nitrogen (mg N L−1), (b) nitrate–nitrogen (mg N L−1), and (c) phosphate–phosphorus (µg P L−1), of inflows (dark gray bars) and outflows (light gray bars) in treatment wetlands compared to those of ambient conditions (black bars). Means are reported with standard error. Single asterisk (*) represents significantly different inflow and outflow values at p ≤ 0.10, while double asterisks (**) represent significantly different inflow and outflow values at p ≤ 0.05. Concentration means reported for Lecheria 1-2, Lecheria 3-4, LaPA, and Planta de Papel wetlands are weighted averages of two inflows. Note that graphs (a) and (c) are on a log scale.

46

Figure 2.7. Relationship between nutrient and oxygen-demanding substance reduction (g m−2week−1) and hydraulic loading rate. Polynomial curves are reported with R2 value. Points represent mean reduction for the five surface-flow wetlands used in this study (Lecheria 1-2, Lecheria 3-4, LaPA, Planta de Papel, and Relleno Sanitario wetlands).

47

CHAPTER 3: EFFECT OF CLIMATE ON METHANE EMISSIONS FROM

TROPICAL FRESHWATER WETLANDS IN COSTA RICA2

3.1 Abstract

Wetlands are one of the largest natural sources of the greenhouse gas methane to the atmosphere. Despite the fact that a large percentage of wetlands occur in tropical latitudes, methane emissions from natural tropical wetlands are not well understood. The objective this research was to compare methane emissions from three natural tropical wetlands located in different climatic and ecological areas of Costa Rica. Each wetland was within a distinct ecosystem: 1) a humid flow-through wetland slough with high mean annual temperatures (25.9 ºC) and precipitation (3700 mm yr-1); 2) a stagnant rainforest wetland with high mean annual temperatures (24.9 ºC) and precipitation (4400 mm yr-1); or 3) a seasonally wet riverine wetland with very high mean annual temperatures (28.2

ºC) and lower mean annual precipitation (1800 mm yr-1). Methane emission rates were measured from sequential gas samples using non-steady state plastic chambers during 6 sampling periods over a 29-month period from 2006-2009. Methane emissions were higher than most rates previously reported for tropical wetlands with means (medians) of

-2 -1 356 (116), 906 (145), and 1004 (371) mg CH4-C m d for the three sites, with highest

2 Nahlik, A.M. and W.J. Mitsch. Submitted for review. Effect of climate on methane emissions from tropical freshwater wetlands in Costa Rica. Global Change Biology. 48 rates seen for the seasonally flooded wetland site. Methane emissions were statistically higher at the seasonally wet site than at the humid sites (p = 0.000). Highest methane emissions occurred when water levels were between 30 and 50 cm. The interaction of soil temperature, water depth, and seasonal flooding most likely affected methanogenesis in these tropical sites. We estimate that Costa Rican wetlands produce about 1.3 Tg yr-1 of methane, or approximately 1 percent of global tropical wetland emissions. Elevated methane emissions at the seasonally wet/warmer wetland site suggests that humid tropical wetlands of Central America may emit more methane if temperatures increase and precipitation decreases in some tropical wetlands with climate change.

3.2 Introduction

Methane is the third-largest concentration of greenhouse gas (GHG) in our atmosphere, following water vapor and carbon dioxide. It is estimated that wetlands emit about 25% of current global methane emissions as a result of prolonged flooded conditions and resulting anaerobic condition that are characteristic of wetlands (Mitsch &

Gosselink 2007), with anthropogenic sources accounting for the remainder (Whalen

2005). Methane is approximately 25 times more effective as a GHG then carbon dioxide

(IPCC 2007); therefore, relatively small changes in methane concentrations could have important impacts on climate. Although much of the estimated 150% increase in atmospheric methane concentration since 1750 can be attributed to landfills, natural gas systems, and ruminant (livestock) farming (Weubbles & Hayhoe 2002), wetlands represent one of the most important natural sources of methane to the atmosphere. It has

-1 been estimated that wetlands contribute between 109 and 145 Tg CH4 yr (20 – 26%) of 49 -1 the total 550 Tg CH4 yr of methane emissions, with boreal and tropical wetlands

-1 contributing the most (24-62 and 42-66 Tg CH4 yr , respectively) (Matthews & Fung

1987; Aselmann & Crutzen 1989; Bartlett & Harriss 1993; Cao et al. 1998; IPCC 2007;

Mitsch & Gosselink 2007). More recent estimates suggest that wetlands may contribute

-1 -1 as much as 180 Tg CH4 yr , with 76% of that (138 Tg CH4 yr ) coming from tropical wetlands (Bergamaschi et al. 2007; Mitsch et al. in press).

It is important to study current wetland methane emissions because temperature increases due to climate change could result in elevated wetland methane emissions, particularly in northern boreal wetlands and tropical wetlands (Cao et al. 1998; Shindell et al. 2004). Despite the fact that tropical wetlands comprise anywhere from 28 to 56% of the world’s wetlands (Mitsch & Gosselink 2007), methane emissions from natural tropical wetlands are not as well understood as are those from temperate and boreal wetlands. There have been many studies on methane emissions from northern boreal regions (45–70°N; Moore & Knowles 1990; Kang & Freeman 2002; Rask et al. 2002;

Huttunen et al. 2003; Song et al. 2009) and temperate regions (30–45°N; Kim et al.

1998; Altor & Mitsch 2006, 2008; Yu et al. 2008); most of the studies on methane emissions from tropical regions have been conducted in rice paddies (Banker et al. 1995;

Husin et al. 1995; Adhya et al. 2000). Furthermore, there are few, if any, studies investigating the effect of different tropical climes (tropical seasonality) on natural wetland methane emissions (Mitsch et al. in press).

The goal of this study is to compare wetland methane emissions from three natural tropical wetlands located in distinctly different climatic and ecological regions of

Costa Rica. We explore the implications of changing climate on methane emissions from

50 tropical wetlands by comparing methane emissions from wetlands currently in different climates. Estimates of wetland methane emissions from countries such as Costa Rica are needed to better understand carbon dynamics in future climates in those countries.

3.3 Materials and Methods

3.3.1 Study sites

Field measurements were collected in three independent, freshwater wetland sites in Costa Rica (Figure 3.1) during six separate site visits to each wetland over a 29-month study from September 2006 through February 2009. The wetlands sites were located at EARTH University, La Selva Biological Station, and Palo Verde

Biological Station. EARTH University and La Selva wetlands are located on the eastern

Caribbean Plain in a tropical rain forest biome while Palo Verde is located on the western

Pacific Slopes in a tropical dry forest biome. All three wetland sites have distinctly different precipitation regimes and experience different climes (Table 3.1).

EARTH wetland (116 ha) is a slow-moving slough within a humid tropical forest undergoing natural restoration after years of grazing. The climate is humid with a 10-

-1 -1 year precipitation average of 3463 mm yr and a mean of 3718 mm yr during the study period. The wetland is dominated by water-tolerant species such as Spathiphyllum friedrichsthalii, Cyrtosperma sp., Raphia taedigera, and Calathea crotalifera, while the surrounding forest is dominated by hardwood tree and palm species such as Pentaclethra macroloba, Terminalia oblonga, Chamaedorea tepejilote, Virola koschnyi, and Virola sebifera (Mitsch et al. 2008). Several large rivers, most notably the Parismina River, run through the EARTH University campus, and the area is susceptible to flooding. Soils are

51 described as poorly-drained alluvial Aquepts on flat relief (Vásquez Morera 1983), and as a result of high vegetative productivity, slow-decomposition, and a high water table, a thick layer of floating mucky peat has developed in the EARTH wetland (Bernal &

Mitsch 2008). Large precipitation events and occasional flooding from nearby creeks influence the hydrology at the EARTH wetland.

The La Selva wetland (3 ha) is situated within a tropical rain forest at the confluence of the Puerto Viejo and the Sarapiqui Rivers and receives a 10-year average of 4639 mm yr-1 of precipitation (4391 mm yr-1 during the study period), the highest mean annual rainfall of the three study sites. The rain forest is dominated by many canopy, subcanopy, and understory tree species, such as Anaxagorea crassipetala, Pentaclethra macroloba, and Rinorea deflexiflora (King 1996). The wetland, however, is relatively open from the forest and hosts large stands of the dominant water-tolerant plant and grass species S. friedrichsthalii and Gynerium sagittatum, in addition to smaller stands of

Asterogyne martiana near the edges. The wetland soils at La Selva have been identified as Tropaquepts by Sollins et al. (1994), and we have observed the typical mottling and high organic matter content associated with these soils at our study site. The combination of a water table near the surface and high year-round precipitation drives the wetland hydrology at the La Selva study site.

Palo Verde wetland (2000 ha) is coastal floodplain freshwater wetland that experiences distinct wet and dry seasons due to both rainfall and occasional river flooding. Palo Verde Biological Station receives the lowest rainfall of the three sites (10- year average of 1248 mm yr-1 and a mean of 1825 mm yr-1 during the study period).

During the wet season, floating aquatic and emergent plants such as Neptunia natans,

52 Nymphaea sp., Eichhornia crassipes, Thalia geniculata, and Typha domingensis dominate, while in the dry season, when the standing water evaporates, grasses and sedges, such as Eleocharis sp., Canna glauca, Cyperus sp., Paspalidium sp., Paspalum repens, Oxycaryum cubense, and Oryza latifolia dominate (Crow 2002). Palo Verde is located at the mouth of the Tempisque River as it flows into the Gulf of Nicoya and finally into the Pacific Ocean. The wetland soils at Palo Verde can be classified as

Vertisols on an alluvial plain; however, the floodplain has been isolated from the river except for exceptional floods by a levee that developed along the river (McCoy &

Rodríguez 1994). The wetland hydrology is largely influenced by wet-season (May-

November) precipitation and runoff from the surrounding watershed.

3.3.2 Methane emission sampling

Non-steady state gas-sampling chambers were used to sample for methane in the wetlands. Twelve chambers were permanently installed in each wetland on two sampling transects. Replicate pairs of chambers were installed in deep water and shallow water sites within the wetland, and upland sites, located away from the wetland where water does not accumulate. The two sampling transects were situated no less than 500 m apart to include as much physical diversity of the wetland as possible. The sampling sites included dominant plant communities when appropriate and were representative of the wetland or upland as a whole.

The permanent PVC (polyvinyl chloride) chambers have proved to be effective in capturing methane emissions from wetlands, inexpensive, and easy to construct (Mitsch et al. 2005; Altor & Mitsch 2006, 2008). Chamber frames consisted of a 0.15 m2

53 rectangular HDPE (high density polyethylene) base, to which a PVC frame measuring approximately 120 cm tall (to ensure that plants remain intact) and covering the basal area of 0.15 m2 was attached. HDPE bases were sunk into the soil to a minimum depth of

10 cm to serve as an air-soil interface. A metal wire was molded around the top frame of each permanent chamber to serve as a thermometer hook.

For deepwater sites (>15 cm in depth), floating chambers, using a modified design from the permanent chambers, were used to collect gas samples. Floating chambers were constructed using a 0.4 m3 frame of PVC over which a 4-mil polyethylene bag, affixed with a 3-m Tygon vent tube (1.6 mm i.d.) and a grey butyl sampling port, was permanently fitted. Buoyant, self-sealing 1.3 cm i.d. pipe insulation constructed of closed-cell polyethylene was affixed to all four sides of the base of the chamber, allowing the chamber to float just under the surface of the water and creating a seal from the ambient environment. A metal wire was molded around the top frame inside each floating chamber to serve as a thermometer hook (Figure 3.2).

Before sampling, non-mercury thermometers with 1°C increments were placed inside of the chambers. At the time of sampling, permanent chamber frames were enclosed by a fitted 4-mil polyethylene bag, affixed with a 3-m Tygon vent tube (1.6 mm i.d.) and a grey butyl sampling port. A 3 cm-wide elastic strap tied tightly around the bag and the base ensured that the chambers were effectively sealed from the ambient environment. After sealing the permanent chamber from the ambient environment or placing the floating chamber on the water surface, gas samples were collected through the sampling port and stored in 10 mL glass vials. Gas samples were taken with a B-D 30 mL syringe fitted with a stopcock immediately upon enclosing the sites and

54 approximately every 5 minutes after the chamber was enclosed. Over a half-hour period, a total of six gas samples were collected from the chamber. Soil, water, and chamber air temperatures and water depth were recorded at each chamber. Soil temperatures at 10 cm in upland sites were not collected to avoid thermometer breakage. After gas samples were collected at one pair of chambers, the bags were removed and used at the next set of permanent chambers. Floating chambers were lifted and moved to the next site.

3.3.3 Meteorological data

Weather stations housing digital precipitation and air temperature data loggers were located on site at EARTH University, La Selva Biological Reserve, and Palo Verde

Biological Reserve.

3.3.4 Processing and analysis

Collected gas samples were transported to the labs at the Olentangy River

Wetland Research Park (ORWRP) at The Ohio State University in Columbus, Ohio, USA and analyzed within 28 days for methane concentrations by flame ionization detection on a Shimadzu GC-14A gas chromatograph equipped with a 40 position HT200H

Autosampler. A 1.8 m Porapak Q column was used for sample separation with helium as

the carrier gas. Matheson methane standards, balanced with N2 gas, were used to perform four-point calibration curves. Check standards, field standards, and/or blanks were run with every tray of 40 samples.

55 Corrected chamber concentrations, by weight, were calculated from the gas chromatograph results and density corrected for chamber volume and temperature:

m = c * (P *M / R * T) [1] where,

-3 m = methane concentration by weight (g CH4 m )

-6 3 -3 3 -3 c = methane concentration by volume (ppmv = 10 cm cm = cm m )

P = atmospheric pressure (assume 1 atm)

M = molecular weight of gas (g mol-1)

R = Universal Gas Constant (82.0575 (atm-cm3)/(mol-K))

T = absolute temperature (K) of the chamber at the time of each sample

The corrected chamber concentrations were converted to milligrams of carbon emission

-3 rates (mg CH4-C m ), and methane flux rates were calculated (Healy et al. 1996; Altor &

Mitsch 2006) according to the following equation:

Fme = [v * (dm/dt) * 1000 / A] *12 / 16 [2] where,

-2 -1 Fme = flux rates (mg CH4-C m h ) v = chamber volume (m3)

A = sample surface area of the chamber (m2)

-3 dm/dt = the slope of the chamber concentration over time (g CH4 m / h)

For each chamber run, the set of six gas sample concentrations were plotted vs. sample time. Regressions were run for each set using Microsoft Excel to determine linearity of emission. Regressions with an R2 < 0.9 were considered non-linear and

56 discarded (Altor & Mitsch 2006). Only linear (positive or negative) emission rates were used in the final analyses. In the case where removal of one to two points corrected the linearity so that R2 ≥ 0.9, those points were discarded from the calculation under the reasoning that disturbances to the bag during attachment at time zero, natural variability in emission rate, and ebullition (release of concentrated methane bubbles) can disrupt linear rates (Holland et al. 1999; Altor & Mitsch 2006). Morning and afternoon methane emission rates for each chamber were averaged to estimate the daily methane emission rate.

3.3.5 Statistical analysis

To compare meteorological data between the wetland sites, analysis of variance

(ANOVA) with a Tukey Pairwise Comparison was used, while t-tests were used to compare 10-year precipitation means to study period precipitation. Pearson correlations were used to determine relationships among the study site properties (i.e., precipitation, air and soil temperatures, and water levels), and ANOVA with a Tukey Pairwise

Comparison was used to compare specific properties between sites. Methane data failed to meet criteria for normal distribution as indicated by Kolmogorov-Smirnov and

Shapiro-Wilk tests of normality. Because methane especially is spatially heterogeneous and natural spikes in emission rates can occur, infrequent high methane rates that passed the rigorous regression standards were not removed as “outliers”. Therefore, non- parametric statistical tests were used for methane emissions. Kruskal-Wallis and Mann-

Whitney tests compared methane emissions between sites and by sampling periods, and

Spearman’s correlations were used to determine relationships between methane

57 emissions and study site properties. Medians are reported along with the means for methane emissions, reflecting the wide distribution of these rates. Unless otherwise specified, reported methane emissions reflect wetland sampling sites (deep and shallow water zones) and do not include upland sampling sites. Significant differences indicate p

≤ 0.05. Statistical analyses were conducted using SPSS Statistics 17.0 for Mac and

Minitab 15.0 for PC.

3.4 Results

3.4.1 Climate, soil temperature, and hydrology

Because the three study sites are located in different biomes in Costa Rica, their climates are distinctly different (Figure 3.3). The total monthly precipitation in each site during the study period proved to be typical, with no significant differences from the 10- year mean of monthly precipitation from the respective site. Likewise, precipitation in each site between years (2007 and 2008) was not significantly different. However, the monthly total precipitation during the study period was significantly different between wetland sites, with Palo Verde receiving less precipitation than EARTH and La Selva (p

= 0.000). Both air and soil temperature negatively correlated to precipitation (pair = 0.045 and psoil = 0.026), and soil temperature positively correlated to air temperature (p =

0.009). Not surprisingly, there were significant differences between mean monthly air temperatures between sites, with Palo Verde experiencing higher air temperatures than either La Selva or EARTH (p = 0.000). Mean soil temperatures during the study were significantly different among all three sites (25.4 ± 0.1, 24.8 ± 0.1, and 28.1 ± 0.2 °C for

EARTH, La Selva, and Palo Verde, respectively; p = 0.000). EARTH wetland had

58 significantly higher mean water levels than Palo Verde and La Selva wetlands (34 ± 2, 11

± 2, and 18 ± 2 cm for EARTH, La Selva, and Palo Verde, respectively; p = 0.000).

Water level did not show a relationship to soil temperatures; however, precipitation was

significantly correlated to water levels at EARTH and La Selva wetland sites (pEARTH =

0.026 and pLaSelva = 0.043).

As expected, water levels from EARTH and La Selva wetlands were significantly correlated to total monthly precipitation (p = 0.026 and 0.043 for EARTH and La Selva, respectively); however, Palo Verde water levels did not correspond to precipitation from the same month, the previous month, or two months previous, which would account for lag between precipitation and water accumulation in the wetland basin. While precipitation may still contribute to water levels at Palo Verde, surface runoff from the

surrounding watershed may be a larger impact on water level in this wetland.

3.4.2 Wetland methane emissions

Over 2,500 gas samples were collected from the EARTH, La Selva, and Palo

Verde wetlands during six sampling periods for a potential 432 total emission estimates.

Nearly 40 percent of the emission estimates were removed due to non-linearity from chamber disturbances; more than 75 percent of these removed estimates were non-linear upland emissions. Less than a quarter of wetland methane emissions were removed due to chamber disturbances.

Hourly methane emissions from the wetland sites ranges were 7-34, 16-56, and

-2 -1 37-47 mg CH4-C m h at EARTH, La Selva, and Palo Verde, respectively (Table 3.2).

Methane emissions varied throughout the study, with similar peaks in methane emissions

59 during high precipitation months (Figure 3.3). Palo Verde wetland showed the least

-2 -1 variance, with the lowest minimum methane emissions reaching 0.4 mg CH4-C m h in

April 2007. Minimum methane emissions from EARTH and La Selva wetlands, on the other hand, frequently were negative, indicating methane oxidation.

Mean methane daily emissions (Figure 3.4) were lower from EARTH than the La

-2 -1 Selva and Palo Verde sites (means of 356, 906, and 1004 mg CH4-C m d for EARTH,

La Selva, and Palo Verde, respectively). Methane emissions for Palo Verde were significantly higher than EARTH and La Selva (EARTH, La Selva, and Palo Verde

-2 -1 methane emission medians of 116, 145, and 371 mg CH4-C m d , respectively; p =

0.000). When the humid sites were pooled, methane emissions were still statistically higher from the seasonally wet site than the humid sites (p = 0.000). The maximum

-2 -1 methane emission from each site (9927, 9621, and 3407 mg CH4-C m d for EARTH,

La Selva, and Palo Verde, respectively) are evidence of occasional high spikes in emissions from the wetlands, while the minimum methane emissions at the sites suggest

-2 -1 that methane oxidation may be important (-148, -97, and 9 mg CH4-C m d for EARTH,

La Selva, and Palo Verde, respectively).

3.4.3 Diurnal methane emissions

Methane samples were collected from the wetlands in the morning (AM) and in the afternoon (PM) to capture diurnal temperature changes, which could affect methane emission rates. There were no consistent differences between AM and PM sampling in the wetlands, nor did median methane emissions significantly differ between a.m. and p.m. at either the EARTH or La Selva wetlands (Table 3.2). Methane emissions were

60 significantly higher in the AM at Palo Verde than in the PM, with median wetland emissions (shallow wetland (S) and deep wetland (D) combined) reduced by nearly 50

-2 -1 percent from 25 in the morning to 12 mg CH4-C m h in the afternoon (p = 0.024).

Deep wetland (D) sites in Palo Verde had significantly higher AM emissions than PM emissions (p = 0.038), while shallow wetland (S) sites within Palo Verde did not differ from AM to PM.

3.4.4 Spatial methane emissions

Methane emissions were significantly lower from soils in the upland sites than in the wetland sites (Table 3.2, p = 0.000). Mean methane emissions from the uplands were

-2 -1 around zero, ranging from -0.5 to 0.4 mg CH4-C m h . When calculated for daily rates, upland methane emission rates from the EARTH and Palo Verde were negative

-2 -1 indicating methane oxidation (-4 and -3 mg CH4-C m d , for EARTH and Palo Verde, respectively). La Selva exhibited a low mean daily methane emission from the upland of

-2 -1 4 mg CH4-C m d , not surprisingly since the upland of La Selva is rainforest and has wet soils. Median upland emissions were not significantly different between wetland sites.

There were no consistent patterns or significant differences in wetland methane emissions between shallow wetland (S) and deep wetland (D) sampling sites in any of the wetlands. Because methane emissions often vary widely within short distances, daily methane emissions at the two transects at each wetland were analyzed separately. In this

-2 -1 analysis, mean methane emissions ranged from 539 mg CH4-C m d (EARTH S) to

-2 -1 1104 mg CH4-C m d (La Selva D). Methane emissions were significantly different 61 between the two transects at EARTH and La Selva (Figure 3.5, p = 0.006 and 0.000 for

EARTH and La Selva, respectively). Median methane emissions were more than three times higher in transect 2 (E2) than in transect 1 (E1) at EARTH wetland, with E2

-2 -1 -2 -1 producing a median of 154 mg CH4-C m d (mean of 518 mg CH4-C m d ). Transect

-2 -1 2 in La Selva (LS2) produced very little methane (6 and 19 mg CH4-C m d , median and mean, respectively), with rates significantly lower than any of the other wetland transects.

On the other hand, transect 1 in La Selva (LS1) produced some of the highest methane

-2 -1 emissions of all the sites (409 and 1350 mg CH4-C m d , median and mean, respectively). LS1 and both the Palo Verde transects are statistically grouped with similar high methane emissions, with no significant difference in median methane

-2 -1 emissions between transects in Palo Verde (medians of 315 and 378 mg CH4-C m d for

PV1 and PV2, respectively) or LS1.

3.4.5 Relationship of methane emissions to physiochemistry

Mean water levels of the transects displayed trends similar to those of methane emissions (Figure 3.5). Although water levels were significantly different between transects at the same wetland (p = 0.000), water levels were similar among wetlands, with no differences between E1, LS1, and PV2 and between LS1 and PV1 water levels.

Despite similar trends in methane emissions, water level was significantly correlated to methane emission only at PV1, LS1, and LS2 (p = 0.037, 0.035, and 0.000 for PV1, LS1, and LS2, respectively).

Mean air temperature did not differ significantly between transects at the same site, but significantly differed among wetlands with Palo Verde exhibiting the highest air

62 temperatures and La Selva exhibiting the lowest (p = 0.000; Figure 3.5a). Methane emissions were not significantly correlated to air temperature at any of the transects.

Mean soil temperature was significantly higher at Palo Verde than the other wetland sites, while EARTH and La Selva soil temperatures were similar with the exception of E1 and LS2, which were significantly different (p = 0.000). Methane emissions were significantly correlated to soil temperature at E2 and LS2. Methane emissions from wetland transects E1 and PV2 failed to correlate with any environmental variable measured in this study.

3.5 Discussion

3.5.1 Tropical methane emissions and climate

The climate experienced by each of the wetlands included in this study was unique, with the largest differences between the humid Caribbean coast wetlands

(EARTH and La Selva) and the seasonally wet Pacific coast wetland (Palo Verde).

Precipitation was correlated to several of the environmental variables, including air and soil temperature, with these conditions driving the development of the surrounding biome

(e.g., humid forest, rainforest, dry forest). Overall methane emissions were highest from the seasonally flooded wetland (Palo Verde), which experienced the highest air and soil temperatures as a result of this seasonality. The Palo Verde ecosystem is in an open, coastal plain with little shading from trees that would be present if this were the humid tropics; this, in turn, contributes to the high temperatures in the wetlands. These physical characteristics of the climate and surrounding environment may explain the high methane emissions rates from this wetland. However, Palo Verde also received seasonal pulsing,

63 with dry periods from December-April and wet periods from May-November, and we expected Palo Verde to have the lowest methane emissions as a result of these drier periods. In a study of temperate wetlands in Ohio, Altor & Mitsch (2008) reported that methane emissions in some locations of these wetlands were significantly lower than in those same locations in steady-flow (non-pulsed) conditions. Husin et al. (1995) also reported similar trends in rice paddies, with less methane produced in intermittently flooded paddies than in permanently flooded paddies. Those pulses were on the order of one week to one month in duration, however, as opposed to the 6-month flooding pulses seen at our seasonal wet Palo Verde site. In comparison to the Palo Verde wetland, the humid tropical La Selva wetland experienced the lowest air and soil temperatures due to heavy precipitation and shading from the rainforest, yet one transect (LS1) from La Selva had large amounts of stagnant (non-pulsed) water and produced as much methane as that found at the Palo Verde transects.

3.5.2 Tropical methane emissions and hydrology

With air and soil temperatures near or slightly above La Selva, the humid tropical wetland at EARTH was continuously flooded but at depths deeper than either of the other two wetlands. Despite large amounts of standing water, methane emissions were lower there than at either of the seasonally flooded Palo Verde transects and transect 1 from La

Selva.

A Shelford-type non-linear relationship (Shelford1912; Odum 1971) was found between methane emissions and average water level when using five of the six sampling site transects included in this study (Figure 3.6). This analysis suggests that there may be

64 an optimal water depth between 30 and 50 cm at which methane is produced in the highest amounts in natural tropical wetlands, and that this range of water depth in concert with temperatures may reflect how water level affects methane emissions with or without pulsing. Several reasons may explain lower methane emissions in the shallow and deep water levels. In shallow water, oxygen diffusion through the air-water interface may be higher, allowing for less anaerobic conditions and more oxidation at the soil-water interface. Additionally, root systems from emergent macrophytes that thrive in shallow water conditions may support methanotrophs in aerobic microsites around oxidized rhizospheres of roots (Gilbert & Frenzel 1995; Segers 1998). On the other hand, carbonaceous material from plant roots can also serve as a reductive substrate (electron donor) for methanogenic bacteria, and elevated methanogenesis has also been reported around plant roots (Segers 1998; Huang et al. 2005). Under very deeper water levels, the wetlands may be experiencing polymictic stratification throughout the day, which could increase methane oxidation of diffuse methane within the water column due to higher dissolved oxygen levels during mixing, which create optimal conditions for methanotrophy (Ford et al. 2002).

3.5.3 Importance of carbon

Most methane production occurs in the top 10 cm of the soil (Crozier et al. 1995), and availability of organic carbon in the substrate is essential for methane production

(Segers 1998). Van der Gon & Neue (1995) found that adding organic matter in rice paddies resulted in higher methane emissions; thus, differences in soil carbon pools in the upper substrate of the wetlands may describe differences in methane emissions. Bernal &

65 Mitsch (2008) measured soil carbon pools in the same wetlands used in the current study.

The concentration of soil carbon for 0-12 cm was very different between sites, with

EARTH, La Selva, and Palo Verde measuring 165, 101, and 43 g C kg-1, respectively; the pattern of methane emissions between sites was inverse to soil carbon concentrations, with Palo Verde emitting the most methane, followed by La Selva, and EARTH emitting the least. When taking into account the different bulk densities among sites, the soil carbon pool was similar for depths between 0-12 cm, measuring 4.41, 4.27, 4.24 kg C m-2 for EARTH, La Selva, and Palo Verde, respectively. Despite potentially large sources of organic carbon from domestic livestock manure at the Palo Verde wetland, soil carbon concentrations or pools did not reflect this. Therefore, the differences in methane emission among the wetlands in this study are unlikely due to differences in soil carbon between sites.

While this study did not include extensive redox potential measurements from the wetlands, we did measure soil redox potentials using platinum electrodes at the EARTH wetland and found that while methane emissions did not correlate with redox in the wetlands, redox in the upland averaged +134 mV and wetlands averaged -147 mV, reaching beyond -250 mV in some areas. Clearly, upland soils at the EARTH wetland were not reduced and wetland soils were reduced to the point of methane production.

Methane emissions can occur even at soil redox potentials as high as -110 mV (Huang et al. 2005). While much of the literature reports a negative correlation between soil redox and methane emission (Huang et al. 2005), others have reported a threshold at which methane is produced but beyond which no correlation occurs (Singh et al. 2000).

Difficulty correlating redox measurements to methane may be due to high spatial

66 variability of both redox and methanogenesis. Boon et al. (1997) reported difficulty measuring redox potential due to the small diameter of the redox probes (< 1mm) and abundant aerobic microsites within the soils.

3.5.4 Spatial variability within wetlands

Our methane emission estimates were highly variable within wetlands, both spatially and temporally. The ranges for each of the wetland sites were 420, 405, and 559

-2 -1 -2 -1 mg CH4-C m h compared to a median of 5, 6, and 15 mg CH4-C m h for EARTH, La

Selva, and Palo Verde, respectively. While Palo Verde had the greatest range of methane emissions, it also had the highest minimum, with methane emissions occurring even during dry periods. One reason that Palo Verde is emitting methane consistently, wet or dry, may be due to the soil characteristics of the wetland. The expanding clay associated with vertisol soils holds water very well, and even when there is no standing water, deeper soils may be saturated and anaerobic, hosting methaneogens. Furthermore, the hot, dry climate of Palo Verde causes cracks in the top layers of soil when the wetland is dry, perhaps allowing for preferential diffusion of methane from deeper, anaerobic layers without interaction from methanotrophs. This hypothesis should be further investigated in Palo Verde and other wetlands dominated by vertisols.

Wachinger et al. (2000) reported large differences in methane production from soil cores extracted within 1 m of each other, with variability sometimes exceeding 100% of the standard deviation. Chen et al. (2009) reported high spatial and temporal variability in methane production both within and among wetland sampling sites in alpine wetlands of China. Methane production varying by several orders of magnitude within

67 small distances is not uncommon (Moore & Knowles 1990; Adrian et al. 1994).

Ebullition, which can account for about 60 percent of the total methane release, can also affect spatial variability, with methane bubbles developing unevenly within a wetland

(Tokida et al. 2005). Isolating the variables that control methane production in the field, especially when the variables are interactive is nearly impossible; therefore, it is not surprising that differences in climate, environmental physiochemistry, or pulsing did not explain the variation in methane emissions between wetlands in this study.

3.5.6 Comparison of methane emissions

-2 -1 Annual methane emissions estimated from this study (173 – 489 g CH4 m yr ) are clearly high compared to reported temperate and boreal methane emission rates. For example, using diffusion chambers in each of the following studies, Altor & Mitsch

-2 -1 (2006) report methane emissions of 28 g CH4 m yr for two temperate created riparian marshes in Ohio using the same field and laboratory techniques used here. By contrast, boreal Canadian peatland annual flux measurements have been reported as less than 10 g

–2 –1 CH4 m yr with primary controlling mechanisms of soil temperature, water table position, or a combination of both (Moore & Roulet 1995). In another central Canadian

–2 –1 boreal wetland study, an average emission of only 1.6 g CH4 m yr was estimated

(Roulet et al. 1992). Methane emissions from a boreal swamp and fen were reported to

-2 -1 emit 4 and 1 g CH4 m yr , respectively (Kang & Freeman 2002); Waddington et al.

-2 -1 (1996) report emissions of 40 g CH4 m yr in a boreal peatland. Methane emission rates published from tropical and sub-tropical wetlands (Table 3) are quite variable and often higher than those of temperate and boreal wetlands. Several of the rates included in

68 Table 3 were reported for large watershed systems such as the Amazon basin (Bartlett et al. 1988; Devol et al. 1988; Melack et al. 2004), river and riparian systems (Boon &

Mitchell 1995; Singh et al. 2000; Yu et al. 2008), and rice paddies (Banker et al. 1995;

Singh et al. 1999; Hadi et al. 2005 (rice paddy)). Published methane emissions for the

-2 -1 wetland types most similar to those used in our study range from 6 to 788 g CH4 m yr ,

-2 -1 with a mean of 302 g CH4 m yr (Devol et al. 1988 (floating macrophyte mats); Snyder

2002; Smith et al. 2000 (floating macrophyte mats); Hadi et al. 2005 (secondary forested

-2 -1 -2 -1 peatland)). The mean (368 g CH4 m yr ) and range (316 g CH4 m yr ) of methane emission rates from our study are within this published range.

3.5.7 Tropical methane emission rates

Our results suggest that the spatial variability of methane emission measurements within one type of wetland are so high as to make previously published global estimates of the methane emissions from tropical wetlands highly problematic. Great attention is paid to the details of mapping wetland systems because the remote sensing capabilities are available to do so, but there is little use of satellite-based estimates if we do not have good field estimates for each wetland type. If we use our average methane emission rate

-2 -1 of 368 g CH4 m yr based on our measurements in two distinct tropical climates and the estimate of Costa Rican wetlands presented by Mitsch et al. (2008) of 3500 km2, we

-1 estimate that tropical wetlands in Costa Rica are producing 1.3 Tg CH4 yr . This is 1

-1 percent of the recent estimate of 138 Tg CH4 yr coming from all tropical wetlands

(Bergamaschi et al. 2007). By comparison, Melack et al. (2004) estimated that the entire

69 -1 mainstem Solimões/Amazon floodplain produced 1.7 Tg CH4 yr , a rate similar to the one we estimated for Costa Rica.

3.5.8 Changes in tropical methane emissions as a result of climate change

Palo Verde, with a drier climate and warmer conditions, may demonstrate how wet and cooler tropical wetlands, such as those at EARTH and La Selva, could transform due to global climate change given a dramatic shift in climate. Using climate models,

Cao et al. (1998) predicted that with a 2°C increase in global temperature, wetland soil carbon would decrease by 10-25% and wetland methane emissions would increase 10-

20%. According to the results of our study, decreased soil moisture (or water level) in humid tropical rainforest wetlands may result in increased methane emissions, especially if water levels fall to “optimal” levels for methanogenesis under higher temperature regimes. Yet, despite predicted increases in tropical wetland methane production under global climate change scenarios, the climate feedback from wetland methane emissions is far lower than those of anthropogenic carbon dioxide emissions (Gedney et al. 2004).

3.6 Conclusions

This study presents methane emission rates for three tropical wetlands in different climates in Central America. Methane emissions measured in the three Costa Rican wetlands were near the maximum values reported for tropical wetlands (including rice paddies and natural wetlands). Methane emissions were highest in wetlands that had standing water between 30 and 50 cm and wetlands that experienced seasonal flooding and warmer temperature. Using Palo Verde wetland as a model for the possible future of

70 some tropical humid rainforest wetlands, methane emissions would increase from tropical wetlands due to increased temperatures and decreased water levels. Additional studies should be conducted in wetlands in other parts of the tropics to validate water level and methane emission patterns described in this paper.

3.7 Acknowledgments

The authors would like to thank Blanca Bernal-Martinez, Bryan Smith, Angela

Adams, and Richard Nahlik for their field assistance in Costa Rica, and Drs. Jane

Yeomans, Stephanie Lansing, and Bert Kohlmann for all their help at EARTH

University. We appreciate site access provided by the Organization for Tropical Studies

(OTS) for La Selva Biological Research Station and Palo Verde Biological Research

Station. Funding for this project came from the United States Department of Energy

(Grant DE-FG02-04ER63834 (EARTH University/OSU Program on Collaborative

Environmental Research in the Humid Tropics; David Hansen, PI)), and from the Wilma

H. Schiermeier Olentangy River Wetland Research Park and the Environmental Science

Graduate Program at The Ohio State University. Olentangy River Wetland Research

Park publication number 2010-00x.

3.8 References

Adhya TK, Mishra SR, Rath AK et al. (2000) Methane efflux from rice-based cropping systems under humid tropical conditions of eastern India. Agriculture, Ecosystems and Environment, 79, 85-90.

Adrian NR, Robinson JA, Suflita JM (1994) Spatial variability in biodegradation rates as evidenced by methane production from an aquifer. Applied and Environmental Microbiology, 60, 3632-3639.

71

Altor AE, Mitsch WJ (2006) Methane flux from created riparian marshes: Relationship to intermittent versus continuous inundation and emergent macrophytes. Ecological Engineering, 28, 224-234.

Altor AE, Mitsch WJ (2008) Pulsing hydrology, methane emissions, and carbon dioxide fluxes in created marshes: a 2-year ecosystem study. Wetlands, 28, 423-438.

Aselmann I, Crutzen PJ (1989) Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions. Journal of Atmospheric Chemistry, 8, 307-358.

Banker BC, Hludze HK, Alford DP, DeLaune RD, Lindau CW (1995) Methane sources and sinks in rice paddy soils: relationship to emissions. Agriculture Ecosystems & Environment, 53, 243-251.

Bergamaschi P, Frankenberg C, Meirink JF et al. (2007) Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations. Journal of Geophysical Research, 112, D02304, doi:10.1029/2006JD007268.

Bernal B, Mitsch WJ (2008) A comparison of soil carbon pools and profiles in wetlands in Costa Rica and Ohio. Ecological Engineering, 34, 311-323.

Bartlett KB, Crill PM, Sebacher DI, Harriss RC, Wilson JO, Melack JM (1988) Methane flux from the central Amazonian floodplain. Journal of Geophysical Research, 93, 1571-1582.

Boon PI, Mitchell A (1995) Methanogenesis in the sediments of an Australian freshwater wetland: Comparison with aerobic decay, and factors controlling methanogenesis. FEMS Microbiology Ecology, 18, 175-190.

Boon PI, Mitchell A, Lee K (1997) Effects of wetting and drying on methane emissions from ephemeral floodplain wetlands in south-eastern Australia. Hydrobiologia, 357, 73-87.

Cao M, Gregson K, Marshall S (1998) Global methane emission from wetlands and its sensitivity to climate change. Atmospheric Environment, 12, 3291-3299.

Chen H, Wu N, Gao YH, Wang YF, Luo P, Tian JQ (2009) Spatial variations on methane emissions from Zoige alpine wetlands of Southwest China. Science of the Total Envirornment, 407, 1097-1104.

Crow GE (2002) Aquatic Plants of Palo Verde National Park and the Tempisque River Valley, 1st edn. Instituto Nacional de Biodiversidad (INBio), Costa Rica. 72

Crozier CR, DeLaune RD, Patrick WJ Jr. (1995) Methane production in Mississippi deltaic plain wetland soils as a function of soil redox species. In: Lal R, Kimble J, Levine E, Stewart BA (Eds.), Soils and Global Climate Change, Lewis Publishers, Boca Raton, FL, pp. 247-255.

Devol AH, Richey JE, Clark WA, King SL (1988) Methane emissions to the troposphere from the Amazon floodplain. Journal of Geophysical Research, 93, 1583-1592.

Ford PW, Boon PI, Lee K (2002) Methane and oxygen dynamics in a shallow floodplain lake: the significance of periodic stratification. Hydrobiologia, 485, 97-110.

Gedney N, Cox PM, Huntingford C (2004) Climate feedback form wetland methane emission. Geophysical Research Letters, 31, L20503, doi:10.1029/2004GL020919.

Gilbert B, Frenzel P (1995) Methanotrophic bacteria in the rhizosphere of rice microcosms and their effect on porewater methane concentration and methane emission. Biology and Fertility of Soils, 20, 93-100.

Hadi A, Inubushi K, Furukawa Y, Purnomo E, Rasmadi M, Tsuruta H (2005) Greenhouse gas emissions from tropical peatlands of Kalimantan, Indonesia. Nutrient Cycling in Agroecosystems, 71, 73-80.

Healy RW, Striegl RG, Russell TF, Hutchinson GL, Livingston GP (1996) Numerical evaluation of static-chamber mesasurements of soil-atmosphere gas exchange: Identification of physical processes. Soil Science Society of America Journal, 60, 740-747.

Holland EA, Robertson GP, Greenburg J, Groffman PM, Boone RD, Gosz JR (1999)

Soil CO2, N2O, and CH4 exchange. In: Robertson GP, Coleman DC, Bledsoe CS (eds.), Standard Soil Methods for Long-Term Ecological Research, Oxford University Press, New York, pp. 185-201.

Husin YA, Murdiyarso D, Khalil MAK et al. (1995) Methane flux from Indonesian wetland rice: the effects of water management and rice variety. Chemosphere, 31, 3153-3180.

Huttunen JT, Nykänen H, Turunen J, Martikainen PJ (2003) Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscandia. Atmospheric Environment, 37, 147-151.

IPCC (Intergovernmental Panel on Climate Change) (2007) Solomon S, Qin D, Manning M et al. (Eds.) Climate Change 2007: The Physical Science Basis.

73 Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, 996 pp.

IPCC (Intergovernmental Panel on Climate Change) (2008) Bates BC, Kundzewicz ZW, Wu S, Palutikof JP (Eds.) Climate Change and Water, Technical Paper, IPCC Secretariat, Geneva, 210 pp.

Kang H, Freeman C (2002) The influence of hydrochemistry on methane emissions from two contrasting northern wetlands. Air, Water, and Soil Pollution, 141, 263- 272.

Kim J, Verma SB, Billesbach DP (1998) Seasonal variation in methane emission form a temperate Phragmites-dominated marsh: effect of growth stage and plant- mediated transport. Global Change Biology, 5, 433-440.

King DA (1996) Allometry and life history of tropical trees. Journal of Tropical Ecology, 12, 25-44.

Matthews E, Fung I (1987) Methane emission from natural wetlands: Global distribution, area, and environmental characteristics of sources. Global Biogeochemistry Cycles, 1, 61-86.

McCoy M, Rodríguez JM (1994) Cattail (Typha dominguesis) eradication methods in the restoration of a tropical, seasonal, freshwater marsh. In: Mitsch WJ (ed.), Global Wetlands: Old World and New, Elsevier Publishing Company, Amsterdam, pp. 469-482.

Melack JM, Hess LL, Gastil M, Forsberg BR, Hamilton SK, Lima IBT, Novo EMLM (2004) Regionalization of methane emissions in the Amazon Basin with microwave remote sensing. Global Change Biology, 10, 530-544.

Mitsch WJ, Zhang L, Anderson CJ, Altor AE, Hernández ME (2005) Creating riverine wetlands: Ecological succession, nutrient retention, and pulsing effects. Ecological Engineering, 25, 510-527.

Mitsch WJ, Gosselink JG (2007) Wetlands, 4th edn. John Wiley & Sons, New York.

Mitsch WJ, Tejada J, Nahlik AM, Kohlmann B, Bernal B, Hernández CE (2008) Tropical wetlands for climate change research, water quality management and conservation education on a university campus in Costa Rica. Ecological Engineering, 34, 276-288.

Mitsch WJ, Nahlik AM, Wolski P, Bernal B, Zhang L, Ramberg L (in press) Tropical wetlands: Seasonal hydrologic pulsing, carbon sequestration, and methane emissions. Wetlands Ecology and Management. 74

Moore TR, Knowles R (1990) Methane emissions from fen, bog and swamp peatlands in Quebec. Biogeochemistry, 11, 45-61.

Moore TR, Roulet NT (1995) Methane emissions from Canadian peatlands. In: Lal R, Kimble J, Levine E, Stewart BA (Eds.), Advances in Soil Science: Soils and Global Change. CRC Press, Boca Raton, FL, pp. 153-164.

Odum, EP (1971) Fundamentals of Ecology, 3rd edn. WB Saunders Co, Philadelphia.

Rask H, Schoenau J, Anderson D (2002) Factors influencing methane flux from a boreal forest wetland in Saskatchewan, Canada. Soil Biology & Biochemistry, 34, 435- 443.

Roulet R, Ash T, Moore TR (1992) Low boreal wetlands as a source of atmospheric methane. Journal of Geophysical Research, 97, 3739-3749.

Segers R (1998) Methane production and methane consumption: a review of processes underlying wetland methane fluxes. Biogeochemistry, 41, 23-51.

Shelford VE (1912) Ecological succession. V. Aspects of physiological classification. Biological Bulletin, 23, 331-370.

Shindell DT, Walter BP, Faluvegi G (2004) Impacts of climate change on methane emissions from wetlands. Geophysical Research Letters, 31, L21202, doi:10.1029/2004GL021009.

Singh S, Singh JS, Kashyap AK (1999) Methane flux from irrigated rice fields in relation to crop growth and N-fertilization. Soil Biology and Biochemistry, 31, 1219-1228.

Singh SN, Kulshreshtha K, Agnihotri S (2000) Seasonal dynamics of methane emission from wetlands. Chemosphere: Global Change Science, 2, 39-46.

Smith LK, Lewis WM Jr., Chanton JP, Cronin G, Hamilton SK (2000) Methane emissions from the Orinoco River floodplain, Venezuela. Biogeochemistry, 51, 113-140.

Snyder JM (2002) Methane emissions from the tropical Atawapaskat wetlands. Journal of Atawapaskat Research, 1, 001-007.

Sollins P, Sancho MF, Mata ChR, Sanford RL Jr. (1994) Soil and soil process research. In: McDade LA, Bawa KS, Hespenheide HA, Hartshorn GS (Eds.), La Selva: Ecology and Natural History of a Neotropical Rainforest. University of Chicago Press, Chicago, pp. 34-63.

75

Song CC, Xu XF, Tian HQ, Wang YY (2009) Ecosystem-atmosphere exchange of CH4 and N2O and ecosystem respiration in wetlands in the Sanjiang Plain, Northeastern China. Global Change Biology, 15, 692-705.

Tokida T, Miyazaki T, Mizogughi M, Seki M (2005) In situ accumulation of methane bubbles in a natural wetland soil. European Journal of Soil Science, 56, 389-395.

Van der Gon HACD, Neue HU (1995) Influence of organic matter incorporation on the methane emission from a wetland rice field. Global Biogeochemical Cycles, 9, 11-22.

Vasquez Morera A (1983) Soils In: Janzen DH (Ed.), Costa Rican Natural History. The University of Chicago Press, Chicago, pp. 63–65.

Wachinger G, Fiedler S, Zepp K, Gattinger A, Sommer M, Roth K (2000) Variability of soil methane production on the micro-scale: spatial associate with hot spots of organic material and Archaeal populations. Soil Biology & Biochemistry, 32, 1121-1130.

Waddington JM, Roulet NT, Swanson RV (1996) Water table control of CH4 emission enhancement by vascular plants in boreal peatlands. Journal of Geophysical Research, 101, 22775-22785.

Whalen SC (2005) Biogeochemistry of methane exchange between natural wetlands and the atmosphere. Environmental Engineering Science, 22, 73-94.

Wuebbles DJ, Hayhoe K (2002) Atmospheric methane and global change. Earth- Science Reviews, 57, 177-210.

Yavitt JB (1997) Methane and carbon dioxide dynamics in Typha latifolia (L.) wetlands in central New York state. Wetlands, 17, 394-406.

Yu K, Faulkner SP, Baldwin MJ (2008) Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration. Global Change Biology, 14, 798-812.

76

Wetland Site Climate Landscape Size (ha) Mean 10-year Annual Rainfall (mm yr-1) EARTH Tropical Humid Restored Humid Forest 116 3463 ± 731 La Selva Tropical Wet Primary Rain Forest 3 4639 ± 618 Palo Verde Tropical Dry Coastal Plains 2000 1248 ± 252

Table 3.1. Description of characteristics of wetlands included in this study. Annual rainfall is reported as mean annual precipitation from 1999 through 2008 ± standard error. Note: 1 ha = 10,000 m2

Table 3.2. Methane emissions and supporting environmental data by wetland site (EARTH, La Selva, Palo Verde) and sampling station (UP = upland, S = -2 -1 shallow wetland, D = deep wetland). Methane is reported as mg CH4-C m h for morning (AM) and afternoon (PM) averages. The daily mean of methane -2 -1 emission is reported as mg CH4-C m d . All values are means ± SE.

77

78

Table 3.3. Methane (CH4) emissions measured for several tropical and sub-tropical wetland and river studies. Study location, biome, field measurement technique, and wetland type are reported for each study. Methane emissions are reported -2 -1 in original units from the source and in g CH4 m yr . Values are overall means or seasonal means from individual studies.

Figure 3.1. Study location sites in Costa Rica and their associated watersheds (shaded in grey).

79

Figure 3.2. Methane gas-sampling chamber design.

80

Figure 3.3. Environmental variables including mean water level (cm), mean soil temperature at 5 cm (°C), mean air temperature (°C), total monthly precipitation (mm mo-1), and mean (lines) and median (markers) methane -2 -1 flux (mg CH4-C m h ) for a) EARTH, b) La Selva, and c) Palo Verde wetland. Error bars on environmental variable data represent standard error, while error bars on the median methane emissions represent the maximum and minimum limits. Note that methane emissions are reported on a log scale. 81 Figure 3.3 continued

Continued

82 Figure 3.3 continued

Continued

83

Figure 3.4. Mean (horizontal lines) and median (circles) wetland methane emission rates -2 -1 (mg CH4-C m d ) for each wetland included in this study. Vertical lines represent minimum and maximum values. Different letters indicate significant differences in medians between groups. Note that methane emissions are reported on a log scale.

84

Figure 3.5. a) Mean air temperature (°C), b) mean soil temperature at 5 cm (°C), c) mean water level (cm), and d) mean (lines) and median (circles) wetland methane -2 -1 emission rates (mg CH4-C m d ) for two separate transects (1 and 2) at EARTH (E), La Selva (LS), and Palo Verde (PV) wetlands. Error bars represent minimum and maximum limits for methane and standard error for environmental conditions. Different letters indicate significant differences between groups using median methane emissions and environmental means.

85

Figure 3.6. Relationship between methane emissions and average water level for each of this Costa Rican wetland study. Line is a second-order polynomial regression through solid data points.

86

CHAPTER 4: EFFECT OF SEASON, HYDROLOGY AND CUMULATIVE

PRODUCTIVITY ON METHANE EMISSIONS IN TWO 13-YEAR-OLD

CREATED WETLANDS3

4.1 Abstract

There have been few studies of methane emissions in created and restored wetlands. We measured seasonal and spatial patterns of methane emissions over a two- year period (2006-08) from two 12 to 14-year-old created wetlands in central Ohio, one initially planted and the other allowed to self-colonize, to determine how season, hydrology, and the original wetland creation approach influence those emissions.

Median (mean) spring/summer methane emissions for the planted and self-colonized

-2 -1 wetlands were 56 (84) and 111 (287) mg CH4-C m d , respectively, while autumn and

-2 -1 winter emissions were considerably lower (11 (28) and 24 (66) CH4-C m d , respectively). Overall, the two created wetlands were different with respect to methane emissions, with the plant self-colonized wetland having higher annual methane emissions

-2 -1 (median and mean emissions of 19 and 68 g CH4-C m y ) than the planted wetland

-2 -1 (median and mean emissions were 6 and 17 g CH4-C m y ). Since hydrology and soil/water temperature were identical for the two wetlands, we hypothesize that

3 Nahlik, A.M. and W.J. Mitsch. In preparation for submittal to Wetlands. Effect of season, hydrology, and cumulative productivity on methane emissions in two 13-year-old created wetlands. 87 differences in carbon accumulation due to higher net primary productivity in the self- colonized wetland may be causing higher methane emissions in that wetland. Net primary productivity in the self-colonized wetland was higher 7 out of 11 years prior to the study. Mean methane emissions from the two created wetlands were 21 and 83 % of

-2 -1 the methane emission of 82 g CH4-C m y measured in a natural wetland in Ohio with similar hydrologic patterns. Annual methane emissions increased at a higher rate in the planted wetland than in the self-colonized wetland over a four-year period with increases

-2 -1 of 4 and 16 g CH4-C m y in the planted and self-colonized wetland, respectively.

Methane emissions from created wetlands in their early decades may depend as much or more on the methods used to create the wetlands (e.g. planting vs. natural colonization) as on the hydrogeomorphic conditions of the wetlands.

4.2 Introduction

Wetland creation and restoration for compensatory mitigation has become commonplace in the USA since the beginning of the ‘no net loss’ policy of the late 1980s related to dredge and fill permit system in §404 of the Clean Water Act. Prior to these mitigation requirements, from the 1950s to 1970s the United States was losing wetlands at a high rate of 185,000 ha yr-1. These losses continued until the mid-1990s, after which slower losses or even gains in wetland areas were observed (Dahl 2006). It is estimated that 178,000 ha of wetlands, with 78,000 ha of this total representing freshwater wetlands, were created in the conterminous United States in the 6-year span from 1998 to

2004 (Dahl 2006). Mitsch and Gosselink (2007) on the other hand, report that 120,000 ha of wetland have been lost from 1993-2005, and that while 237,000 ha of mitigation

88 credit has been administered, “success” or even completion of many of these mitigation wetlands has not been documented.

Wetlands are the largest natural source of methane emissions (IPCC 2007) and responsible for contributing about 25 percent of methane emissions to the atmosphere

(Whalen 2005). Anaerobic conditions, low reduction-oxidation potential in the soil, and high availability of organic carbon are typical characteristics of wetlands and also optimal conditions for the production of methane. As a greenhouse gas (GHG), methane is of particular concern due to the fact that its global warming potential (GWP) is 25 times that of carbon dioxide (IPCC 2007) after 100 years. A concern expressed by some (Bridgham et al. 2006) with regards to wetland creation and restoration is the positive climate forcing potential or net radiative forcing that these new ecosystems may have by producing greenhouse gases (GHG) such as methane.

Despite efforts to increase wetland area in the United States, there are still uncertainties over how much wetland area has been gained and concerns over the unmitigated loss of wetlands due to global climate change, exportation of wetlands, shifts in wetland types, and loss of function (Campbell et al. 2002, Cole and Shafer 2002, Robb

2002, Zedler 2004, Hoeltje and Cole 2007, Kettlewell et al. 2008). It is indisputable that we have experienced a net loss of wetlands from 1950 to 1994 in the United States (Dahl

2000, 2006); yet, global methane emissions to the atmosphere are estimated to have

-1 increased by about 150 Tg CH4 yr over roughly the same period (Wuebbles and Hayhoe

2002). Most increases in methane emissions during that period are likely due to anthropogenic practices, such as cattle production and solid waste landfills. Yet methane

89 emissions from wetland creation and restoration remain a concern among some scientists and professionals (Bridgham et al. 2006).

Methane emissions have been well-studied in natural boreal peatlands (Moore and

Knowles 1990, Shannon and White 1994, Moosavi et al. 1996, Rask et al. 2002,

Huttunen et al. 2003), natural temperate wetlands (Wilson et al. 1989, Huang et al. 2005,

Rose and Crumpton 2006, Smemo and Yavitt 2006), and highly-managed created wetlands, such as rice paddies (Husin et al. 1995, Naser et al. 2007, Gogoi et al. 2008).

There have been fewer studies, however, on methane emissions from created wetlands in seasonal temperate climates. Our study is a follow-up at the same created wetlands in

Ohio where Altor and Mitsch (2006, 2008) suggested that methane emissions were reduced under a dynamic, pulsing hydrology compared to a static, steady-flow hydrology.

That study suggested that creating wetlands with a varying hydroperiod may suppress methane emissions and that highest rates of methane emissions were in deeper waters.

The objective of our current study is to compare two 13-year-old created wetlands, one of which was planted and the other of which was left to naturally colonize, under the same climate, hydrological, and edaphic conditions (Mitsch et al, 1998, 2005). We are also able to investigate trends in methane emissions in these wetlands two years after the Altor and Mitsch (2006, 2008) study and to compare our rates to those in natural wetlands in similar hydrogeomorphic conditions.

90 4.3 Methods

4.3.1 Study site

This study took place in two experimental wetlands at the Olentangy River

Wetland Research Park (ORWRP) at The Ohio State University in Columbus, Ohio.

Two 1-ha kidney-shaped wetlands were excavated on an abandoned agricultural field in

1993, adjacent from the Olentangy River with water first added by a pumping system in

March 1994 (Mitsch 2005; Mitsch et al., 1998, 2005). The wetlands were created as mirror images with the same basin morphology; however, the western basin (Wetland 1) was planted with 13 native species of macrophytes (Mitsch et al., 1998) while the eastern basin (Wetland 2) was allowed to naturally colonize. Water from the Olentangy River, which is located in the primarily agricultural Scioto River Watershed, is pumped to the experimental wetlands. Pumping rates are the same for each of the two wetlands; rates can be adjusted depending on experimental investigations but they have always been the same for both wetlands. Although vegetation patterns vary from year to year, during this study Wetland 1 was dominated by Sparganium eurycarpum Engelm. (giant bur-reed),

Typha angustifolia L. (narrow-leaved cattail), Typha latifolia L. (common cattail), Typha

× glauca Godr. (T. latifolia x T. angustifolia hybrid), Scirpus fluviatilis (Torr.) M.T.

Strong (river bulrush), Schoenoplectus tabernaemontani (C.C. Gmel.) Palla (soft-stem bulrush), and Leersia oryzoides (L.) Sw. (rice-cut grass). In contrast, Wetland 2 has fewer dominant plant communities, mostly as T. angustifolia, T. latifolia, T. glauca, L. oryzoides, and S. tabernaemontani. Phragmites australis (Cav.) Trin. ex Steud.

(common reed) recently invaded this wetland but still covered a small fraction of the wetland during this study. The two wetlands have been extensively studied since their

91 creation, and data regarding development in water quality, plant community structure, soil characteristics, sedimentation, and gas exchange has been routinely published

(Mitsch et al. 1998, 2000, 2005a,b, 2008; Wu and Mitsch 1998; Kang et al. 1998; Nairn and Mitsch 1999; Spieles and Mitsch 2000a,b; Harter and Mitsch 2003; Anderson et al.

2005; Altor and Mitsch 2006, 2008; Anderson and Mitsch 2006; Hernández and Mitsch

2006, 2007a,b; Tuttle et al. 2008; Nahlik and Mitsch 2008).

An additional site with similar hydrogeomorphic characteristics to the ORWRP wetlands was measured as a natural reference wetland for comparison to the two created wetlands. The reference wetland is located in northern Ohio on Lake Erie. The 56-ha

Old Woman Creek wetland receives water from primarily agricultural Huron County.

Occasionally, storm waves or seiches break the sand barrier between the wetland and

Lake Erie, and lake water flows into the wetland. These events occur only a few times per year, generally in the cooler months and when lake water levels are high. Dominant plant communities at Old Woman Creek include Nelumbo lutea Willd. (American Lotus),

T. angustifolia, T. latifolia, and P. australis. Old Woman Creek has been researched in regard to nutrient removal, sediments, and vegetation communities (Mitsch and Reeder

1991, 1992, Krieger 2003, McCarthy et al. 2007, Bernal and Mitsch 2008, Scott et al.

2008, Whyte et al. 2008, Mitsch et al. in press).

4.3.2 Experimental design

This study took place over a 25-month period, from July 2006 through August

2008. Throughout the study period, pumping rates were adjusted daily according to a predetermined formula based on the flow of the Olentangy River so that the wetlands

92 experienced conditions similar to naturally occurring riverine wetlands. The same amount of water is introduced to each wetland. From November to April, during typically cold (mean air temperature for the study period was 4°C) and wet conditions in

Ohio, the wetlands generally experience more frequent flooding and higher water levels.

During the warm (mean air temperature for the study period was 21°C) and dry seasons from May to October, the water level is usually lower in the wetlands due to low river flow.

Twelve permanent non-steady state gas-sampling chambers described in other studies (Mitsch et al. 2005, Altor and Mitsch 2006, 2008, Chapter 3) were installed in each experimental wetland several weeks prior to the start of this study. Chambers were installed in replicate pairs at upland, shallow water, and deep water sites in the inflow and outflow areas in each wetland (Figure 4.1). Upland sites remained dry throughout the study period, whereas shallow and deep water sites were within the wetland boundaries, with shallow sites closer to the edge and deep sites near the middle of the wetland.

Chamber sites included dominant plant communities and chosen to represent the vegetative structure and geomorphology of the wetland.

4.3.3 Methane sampling

Gas-sampling chambers were constructed of a 0.26 m2 rectangular HDPE base

(high density polyethylene) that was sunk a minimum of 10 cm into the soil for a soil-air interface. A PVC (polyvinyl chloride) frame of the same basal area as the base and measuring 120 cm tall to allow for emergent plants within the chamber was attached to

93 the base. Metal wires were attached to the top of each PVC frame for the placement of a thermometer inside the chamber.

The permanent chamber design was modified for floating gas-sampling chambers, which were used when water depths exceeded 15 cm (typically deep water sites). The floating chambers were constructed using a 0.4 m3 PVC frame over which a 4-mil translucent polyethylene bag, equipped with a 3-m Tygon vent tube (1.6 mm i.d.) and a grey butyl sampling port, was permanently fitted. To seal the chamber with the water and promote buoyancy, closed-cell polyethylene pipe insulation (1.3 cm i.d.) was attached to the base of the frame. Thermometers were permanently installed vertically

(hanging on the side) and horizontally (taped to the top) inside the floating chambers to allow for accurate readings.

At the time of sampling, non-mercury thermometers with 1°C increments were placed inside each permanent chamber. A fitted 4-mil translucent polyethylene bag, equipped with a 3-m Tygon vent tube (1.6 mm i.d.) and a grey butyl sampling port, was placed over the frame of the permanent chamber, and a 3 cm-wide elastic strap was tied tightly around the bag and base of the chamber. In the case of deep water, the floating chambers were simply placed on the water surface alongside the open permanent chamber. Immediately after sealing the chambers, the initial sample was collected through the butyl sampling port using a B-D syringe fitted with a stopcock. 30 mL of air was drawn from the chamber and placed into pre-evacuated 10mL glass vials. After the initial sample, five additional samples spaced at five-minute intervals were collected.

The chamber air temperature and time (h:min:sec) were recorded for each sample collected, and soil and water temperatures and water depth were measured once at each

94 chamber. Upon collection of all six gas samples, the bags were removed from the permanent chamber to be used with another set of chambers, or the floating chambers were lifted and moved to the next sampling site. Chambers were sampled in the morning and afternoon of the same day to capture daily variation in methane emission due to diurnal temperature fluctuations.

4.3.4 Gas analysis

Gas samples were stored at 4°C for no longer than 28 days until analysis on a

Shimadzu GC-14A gas chromatograph (GC) equipped with a 40 position HT200H

Autosampler located at the ORWRP. Samples were separated through a 1.8 m Porapak Q column with helium as the carrier gas and analyzed for methane concentrations using

flame ionization detection. Matheson methane standards, balanced with N2 gas, were used to perform four-point calibration curves. Check standards, field standards, and/or

-2 -1 blanks were run with every tray of 40 samples. Methane flux rates (mg CH4-C m h ) were calculated from trend regressions of methane concentrations from the GC (Healy et al. 1996, Altor and Mitsch 2006). The equation that was used for this conversion is detailed in Chapter 3).

Regressions for each set of samples plotted vs. time were used to determine linearity of emission. Regressions with R2 < 0.9 were considered non-linear and corresponding samples were rejected; only linear positive and negative regressions were used. Up to two points may have been removed in a regression if it corrected the linearity under the reasoning that disturbances to the bag or release of methane bubbles through the process of ebullition may disrupt linear rates (Holland et al. 1999, Altor and

95 Mitsch 2006). Morning and afternoon methane emission rates were averaged for each chamber to estimate daily emission rates.

4.3.5 Hydrology

Two-per-day manual staff gage readings for the two created wetlands were averaged for the duration of the study period. Staff gage readings were highly correlated with manual water depth readings taken during methane emission measurements within the wetland chambers (R2 > 0.8, p ≤ 0.006), allowing accurate estimation of water levels within each chamber for the study period.

4.3.6 Wetland macrophyte productivity

Above-ground macrophyte net primary productivity (NPP) of the two created wetlands has been estimated annually from peak biomass as it occurs in late summer in each of the two experimental wetlands since 1997 (Mitsch et al. (2005b, 2009) and are used in this study to explain possible difference in the two wetlands in regards to methane emissions.

4.3.7 Statistical analysis

Methane data failed to meet conditions of normality according to Kolmogorov-

Smirnov and Shapiro-Wilk tests; therefore only non-parametric statistics were used to analyze methane data. Kruskal-Wallis and Mann-Whitney tests compared methane emissions between seasons, sites, and wetlands, and Spearman’s correlations were used to determine relationships between methane emissions and study site properties. Because

96 non-parametric tests are based on median values, methane data is consistently reported with medians and means. Spatial heterogeneity in methane emissions and natural spikes result in infrequent high methane rates that passed the rigorous regression standards.

These high methane rates were not removed as “outliers”, and reported maximum and minimum values on graphs reflect the high variability in emission rates. Methane emissions are seasonally-weighted unless otherwise noted because more samples were collected during the summer than other seasons. Values discussed in the results are for wetland (shallow water and deep water combined) sites and do not include upland sites unless otherwise specified. Comparisons of environmental data, hydrology, and productivity between wetlands were completed using t-tests, analysis of variance

(ANOVA) with a Tukey Pairwise Comparison, or Pearson correlations, where appropriate. Significant differences indicate p ≤ 0.05. Statistical analyses were conducted using SPSS Statistics 17.0 for Mac and Minitab 15.0 for PC.

4.4 Results

A total of 2,016 gas samples were collected between the two wetlands during the

25-month study period yielding a maximum possible number of methane emission estimates of 336. Approximately 75% of the upland gas samples were discarded due to non-linearity, while fewer than 45% of the wetland gas samples were discarded. Wetland

2 tended to have less variability (i.e., fewer disruptions) within the chambers, resulting in

22% more linear wetland methane rates than Wetland 1. Seasons tended to affect linearity of sample sets, with almost 65% of the winter and spring wetland methane

97 emission rates discarded, but only 38% of summer and autumn wetland emission rates discarded.

Seasonally-weighted methane emissions for the year were significantly higher in the naturally colonizing wetland (Wetland 2) than in the planted wetland (Wetland 1),

-2 -1 with median (mean) rates of 19 (68) and 6 (17) g CH4-C m y respectively (p = 0.015,

Figure 4.2). However, paired t-tests for individual methane measurements between wetlands showed that Wetland 2 was not consistently higher than Wetland 1. Paired t- tests did confirm that methane emissions from shallow water sites were significantly higher in Wetland 2 than in Wetland 1 (p = 0.050), but there was not a significant difference for deep water sites between wetlands.

4.4.1 Seasonal patterns and effect of soil temperature

Seasonal patterns in methane emissions (Figures 4.3 and 4.4) show that the planted Wetland 1 had significantly higher rates during the summer than any other season

(p = 0.001). Mean summer methane emission rates were 96 and 58% higher than winter methane emission rates in Wetland 1 and 2, respectively. Median (mean) summer

-2 -1 emission rates were 80 (151) mg CH4-C m d in Wetland 1, more than 4 times higher than median emission rates from spring, 10 times higher than autumn rates, and 8 times higher than winter rates. Spring and summer methane emissions were not significantly different for the naturally colonizing Wetland 2 (Figures 4.3 and 4.4), with median

-2 -1 (mean) emission rates of 135 (277) and 87 (297) mg CH4-C m d for spring and summer, respectively. Summer methane emission rates in Wetland 2, however, were significantly higher than those of autumn and winter (p = 0.007, 0.056) while spring

98 emissions were not different than those of winter. Median (mean) emission rates of 37

-2 -1 (122) mg CH4-C m d for autumn in Wetland 2 were significantly lower than both spring and summer emissions, but not winter emissions.

Soil temperatures fluctuated seasonally (Figure 4.3) in a pattern similar to the methane emissions. Seasonal air temperatures and soil temperatures were highly correlated in both wetlands (p = 0.001, 0.000 for Wetland 1 and Wetland 2, respectively), and soil temperatures in Wetland 1 and 2 were an average of 20.0 and 23.2 °C lower in the winter months than the summer months. Mean soil temperatures for summer, autumn, winter, and spring were 23.7, 4.7, 3.7, and 12.9 ºC for Wetland 1 and 26.3, 5.4,

3.1, and 14.0 ºC for Wetland 2. Methane emissions were weakly correlated with soil temperatures in each wetland (Figure 4.5; p = 0.057, 0.093 for Wetland 1 and Wetland 2, respectively) despite methane emissions from both wetlands following very similar seasonal patterns, with emission rates peaking with the highest soil temperatures and lowest with the lowest soil temperatures (Figures 4.3 and 4.5). Soil temperatures were not significantly different between the two wetlands. Despite that, methane emissions were significantly higher in Wetland 2 than in Wetland 1. The difference in methane

- emissions between Wetland 1 and Wetland 2 at 10 °C was approximately 3 mg CH4-C m

2 h-1 (Figure 4.5).

4.4.2 Effects of hydrology

There were no significant differences between water levels in Wetland 1 and

Wetland 2. The hydrology of the wetlands fluctuated from month to month, reflecting variations within the river, with large pulses primarily occurring in the cold, wet season

99 (Figure 4.3). Water levels at shallow water chambers (means of 9.5 and 11.9 cm for

Wetland 1 and Wetland 2, respectively) were significantly lower than those at deepwater chambers (means of 24.5 and 21.7 cm for Wetland 1 and Wetland 2, respectively; p =

0.000 for both Wetland 1 and Wetland 2). Shallow water sites were shallower in

Wetland 1 than in Wetland 2 by an average of 2.4 cm (p = 0.000), while deep water sites were shallower in Wetland 2 than in Wetland 1 by an average of 2.8 cm (p = 0.000).

However, mean chamber water depth for shallow and deep water sites combined was not significantly different between wetlands. Chamber sites completely dried only twice during the study—in August 2006 and August 2007—as a result of planned pump shut downs during annual peak biomass measurements.

Median (mean) methane emissions for upland sites in both Wetland 1 and

-2 -1 Wetland 2 were 3 (0) mg CH4-C m d , while there was significantly more methane emitted from shallow and deepwater sites (Figure 4.6). Shallow water sites emitted

-2 -1 -2 -1 medians (means) of 37 (36) mg CH4-C m d and 77 (160) mg CH4-C m d in Wetland

1 and 2, respectively. Although deepwater sites did not have significantly different methane emissions than did shallow water sites, median methane emissions of deepwater sites compared to shallow water sites were 68 and 52% lower in the deepwater sites for

Wetland 1 and 2, respectively (Figure 4.6).

4.4.3 Natural reference wetland

The natural reference wetland at Old Woman Creek included in this study was found to emit methane at annual median (mean) methane emission rates of 23 (82) g

-2 -1 CH4-C m y – the mean rate of which is over 2.5 times that of either created wetland 100 (Figure 4.5). However, median methane emissions from Old Woman Creek are only significantly higher than those of Wetland 1 (p = 0.003). Soil temperatures in Old

Woman Creek were also significantly higher than those in Wetland 1 (p = 0.032), but the same as Wetland 2. This may be causing the natural wetland to emit more methane than the created wetlands, especially Wetland 1, at the same temperatures (Figure 4.5).

Methane emissions followed the same patterns in Old Woman Creek as the two created wetlands, with significantly higher methane emitted from wetland sites than upland sites

(p = 0.009) and no difference between shallow and deep water wetland sites (Figure 4.6).

4.5 Discussion

4.5.1 Effects of soil temperature (season) and water depth

The positive relationship between soil temperature and methane emission rates in this study is consistent with the literature (Koch et al. 2007, Chen et al. 2008, Koh et al.

2009). Although a clear relationship between hydrologic gradients and methane emissions was not seen in the current study, others have reported higher methane emissions in deep, permanently flooded compared to shallow, temporarily flooded wetland areas (Whalen and Reeburgh 2000, Altor and Mitsch 2006, 2008, Koh et al.

2009). Regardless of the relationships between season and water depth on the one hand and methane emissions on the other, this could not explain the differences seen between the two experimental wetlands in this study because there was no difference between climate or hydrology between the two wetlands.

Water depths near the permanent gas-sampling chambers in only the shallow water areas were different between the two wetlands. Chamber water depths in the

101 shallow areas of the colonized wetland had a mean of 10 cm, whereas those of the same area in the planted wetland had a mean of 8 cm. This indicates that chambers were installed in slightly deeper water than in the planted wetland. Paired t-tests did show that methane emissions in shallow water were significantly higher in the colonized wetland than the planted wetland. However, methane was not significantly correlated to water level, and the 20% difference (2.4 cm) in water depth between sites is unlikely to have resulted in the large difference in methane emission rates between wetlands.

4.5.2 Comparison with past studies at the same created wetlands

Despite the same seasonal patterns of solar energy, air and soil temperatures, and general hydrology in both experimental wetlands, the self-colonized wetland (Wetland 2) produced approximately 70% more methane than did the planted wetland (Wetland 1).

Methane emission rates for Wetland 1 and Wetland 2 during the current study are similar to slightly higher than those measured in the same wetlands by Altor (2007) in 2004-2005

(Figure 4.7; Table 4.1). For both studies, methane emissions for individual wetlands are higher in Wetland 2, the self-colonized wetland, than in Wetland 1, the planted wetland, suggesting that this result is consistent at this site regardless of hydrologic regime.

Mean methane emissions between the two wetlands was highest under steady-

-2 -1 flow conditions in 2005, and the mean reported for this study, 42 g CH4-C m y , is within the reported range for previous studies. The hydrology during our study was more natural because it followed that of the river, in comparison to heavily pulsed and evenly steady-flow hydrologic regimes purposely staged in 2004 and 2005. The natural hydrology was characterized by many small fluctuations, with some larger pulses and

102 some steady-flow periods – something between the 2004-2005 regimes. Therefore, it is not surprising that the mean methane emissions for both wetlands combined during this study were lower than those under a steady-flow regime and higher than those under a pulsed regime. Higher methane emissions under steady-flow hydrology than pulsed hydrology have been reported in several rice paddy studies, which have been better researched in regards to water management and methane emissions than natural or created wetlands (Mishra et al. 1997, Rath et al. 1999, Wang et al. 1999). Altor and

Mitsch (2008) reported that methane emissions in the same wetlands as this study were consistently higher in deep water sites under steady-flow conditions than pulsing conditions. We found no significant difference between the shallow and deep water sites in this study. One reason may be the differences in hydrologic regimes between this study and that conducted by Altor and Mitsch; the heavily-pulsed regime in 2005 may have affected the shallow water sites in such a way that standing water did not occur for long-periods of time.

4.5.3 Methane emissions and wetland macrophyte productivity

Differences in macrophyte net primary productivity between the wetlands, reported by Mitsch et al. (2005b, 2009) for the period 1997 through 2007, may explain the differences in methane emission rates. Net primary productivity (NPP) in the wetlands averaged 619 ± 76 and 751 ± 83 g-dry wt m-2 y-1 for Wetland 1 and Wetland 2, respectively over this period (Table 4.2). Although there was no significant difference in

NPP between the two wetlands over the 11 years, NPP was greater in Wetland 2 than in

Wetland 1 by an average of 313 g-dry wt m-2 y-1 (60%) during 7 of the 11 years. NPP in

103 Wetland 1 exceeded that of Wetland 2 in only in years 2002, 2003, 2006, and 2007.

Cumulative productivity after 11 years remained 3754 kg ha-1 (9%) greater in Wetland 2 after 11 years.

Methane emissions tended to increase from 2004 and 2007, but with different slopes (Figure 4.7a). Methane emissions from the colonized wetland (Wetland 2)

increased substantially from 2004 to 2007, with an annual rate of increase of 16 g CH4-C m-2 y-1. The planted wetland (Wetland 1), on the other hand, only showed an annual rate

-2 -1 of increase of 4 g CH4-C m y . Differences in methane production trajectories between wetlands are hypothesized to be due to different initial conditions in 1994 when on wetland was planted and the other not. This suggests that planting wetlands after they are created can actually lead to lower productivity and subsequent lower annual methane production for several years.

Using these annual productivity data collected in both wetlands and methane data reported for the two wetlands for 2004-05 by Altor (2007), we found that from 2004 to

2007, mean annual methane emissions for the experimental wetlands increased linearly,

-2 -1 from 28 to 49 g CH4-C m y as cumulative productivity, some of which translates to permanent soil carbon, increased in both wetlands from 26 to 38 Mg ha-1.

When data are separated for each wetland, the resulting 8 data points over 4 years

-2 -1 suggest an average increase of 3 g CH4-C m y for every Mg of cumulative productivity

(Figure 4.7b). Similar relationships between methane emission and net ecosystem productivity (NEP) for different wetland types were reported in Whiting and Chanton

(1993). Biomass and methane emissions have also been shown to have a strong, positive relationship (Whiting et al. 1991). Whiting and Chanton (1993) demonstrated that

104 wetlands dominated by T. latifolia, one of the cattail species that is found in the self- colonized wetland in this study, had the highest NEP and methane emissions. The reported June methane emission rate for a T. latifolia marsh in Florida, USA was

-2 -1 approximately 350 mg CH4-C m d (Whiting and Chanton 1993), only slightly higher

-2 -1 than the mean rate of 297 mg CH4-C m d measured in the self-colonized wetland

(Wetland 2) during summer in our study.

Although the planted wetland in this study had lower productivity than the self- colonized wetland, it has consistently higher community diversity than the self-colonized wetland, most likely because there are less aggressive plants dominating the planted wetland, allowing more species to become established (Mitsch et al. 2009). This is also reflected in the number of dominant plants in each wetland as discussed by Mitsch et al.

(2005b). In a mesocosm study of macrophyte functional group richness, Bouchard et al.

(2007) found that increased functional guild richness resulted in higher belowground biomass and decreased methane emissions. Although macrophyte functional groups like those studied in Bouchard et al. (2007) have not been specifically identified for the wetlands in this study, it is likely that more functional groups are present with the higher community richness in the planted wetland (Wetland 1). This should be further investigated in these wetlands.

Vegetation influences methane emissions positively by promoting gas exchange from the sediments to the atmosphere through plant stems. Methane is transported through Typha sp. stems by convective throughflow, the process of gas moving from high pressure to low pressure gradients (Whiting and Chanton 1996). Other species, such as S. eurycarpum, which dominated the planted wetland of this study, have also been reported

105 to effectively transport methane from sediments to the atmosphere (King 1996). We did not investigate the capacity of different dominant plant species in the two wetlands to channel methane, but this may be an important study to conduct in the future.

Vegetation also positively influences methane emissions by sequestering soil carbon. Despite the higher productivity in the self-colonized wetland compared to the planted wetland, Anderson and Mitsch (2006) were not able to find a significant difference in organic carbon (OC) accumulation between the wetlands even though in

2004, when the study was conducted, percent OC of the soils were 3.5 ± 0.1 and 3.7 ± 0.2 for the planted and colonized wetland, respectively. It was observed that sediment accumulation in deep zones of the colonized wetland were higher than the same areas in the planted wetland (Anderson and Mitsch 2006). This is consistent with our findings that the deepwater sites were slightly shallower in Wetland 2 than in Wetland 1, suggesting that it may be filling up quicker with autochthonous production.

4.5.3 Comparison with natural wetland emissions

Methane emissions from the created wetlands at the ORWRP were lower than most reported methane emissions using similar methods for natural temperate wetlands

(Table 4.1). Old Woman Creek, the natural wetland used as a reference in this study, had

-2 -1 a mean methane emission rate of 82 g CH4 g CH4-C m y , which is 79% higher than the planted created wetland (Wetland 1) and 17% higher than the colonized created wetland

-2 -1 in this study. Other reported natural wetland emission rates range from 62 CH4-C m y

-2 -1 for wetlands in Virginia (Whiting and Chanton 2001), 35 g CH4 g CH4-C m y in

-2 -1 temperate forested wetlands (Bartlett and Harriss 1993), 51 g CH4-C m y in spring-fed 106 -2 -1 wetlands in Mississippi (Koh et al. 2009), to 80 g CH4-C m y for a marsh in Nebraska

(Kim et al. 1999).

The above comparison suggests that methane emissions in these created wetlands will continue to increase to a plateau, with the planted wetland reaching natural wetland emissions in 25 years, or 40 years after wetland creation, and the self-colonized wetland reaching natural wetland emissions in less than 10 years, or 20 years after wetland creation (Figure 4.8). Overall, planting may have decreased methane emissions by 0.8 kg

-2 CH4-C m since the creation of these wetlands. One possible explanation for increases in methane emissions from created wetlands over time is increasing soil carbon from productivity also provides substrate for methanogens to produce methane as illustrated by

Figure 4.7b. There is a positive relationship between methane emissions and cumulative productivity when the planted and self-colonized wetlands are combined. Soil carbon development explains why natural wetlands have higher methane emissions than the created wetlands in this study.

4.6 Conclusions

The long-term study at the ORWRP has shown that planting a created or restored wetland in the initial stages of development alters the long-term development of that wetland by promoting greater species richness in exchange of productivity (Mitsch et al.

2005, 2008). Gutrich et al. (2009) also reported that created marshes with high initial efforts (i.e., planting) had higher species richness than marshes created with low initial effort. This study is unique in that it is the first to compare methane emissions between created wetlands with different initial conditions and suggests that planting as a wetland

107 management technique may indirectly result in lowered methane emissions. Planting seems to slow the rate at which methane emissions increase over time. The mechanism by which methane was enhanced in the self-colonized wetland is not known, but could be due to the higher cumulative productivity found at that wetland. Future studies are needed to determine the generality of these findings to other created freshwater wetlands.

4.7 Acknowledgments

The authors would like to thank Anne Altor, Kyle Chambers, Chris Cooley,

Blanca Bernal Martinez, Eric Emerson, Dan Fink, Maria Hernández, Chen Huang, Matt

McCaw, Lukas Moe, Monica Noon, Abby Rokosch, Keunyea Song, Evan Waletzko,

Ryan Younge, and Dr. Li Zhang for all their teamwork in the field. My doctoral committee, Dr. Nick Basta, Dr. Richard Dick, and Dr. Jay Martin, provided comments and suggestions that improved this manuscript. Thank you to Dave Klarer and Frank

Lopez at Old Woman Creek for all their hospitality and assistance at their beautiful wetland site – we always enjoyed our days of fieldwork there. Funding for this project came from the United States Environmental Protection Agency (US EPA Agreement

EM83329801-0), the Wilma H. Schiermeier Olentangy River Wetland Research Park, and the Environmental Science Graduate Program at The Ohio State University.

Olentangy River Wetland Research Park publication number 2010-00x.

4.8 References

Altor, A. E. 2007. Methane and carbon dioxide fluxes in created riparian wetlands in the Midwestern USA: effects of hydrologic pulses, emergent vegetation and hydric soils. Ph.D. Dissertation. The Ohio State University, Columbus, OH, USA.

108

Altor, A. E. and W. J. Mitsch. 2006. Methane flux from created riparian marshes: Relationship to intermittent versus continuous inundation and emergent macrophytes. Ecological Engineering 28:224-234.

Altor, A. E. and W. J. Mitsch. 2008. Pulsing hydrology, methane emissions, and carbon dioxide fluxes in created marshes: a 2-year ecosystem study. Wetlands 28:423- 438.

Anderson, C. J., W. J. Mitsch, and R. W. Nairn. 2005. Temporal and spatial development of surface soil conditions at two created riverine marshes. Journal of Environmental Quality 34:2072-2081.

Anderson, C. J. and W. J. Mitsch. 2006. Sediment, carbon, and nutrient accumulation at two 10-year-old created riverine marshes. Wetlands 26:779-792.

Bartlett, K. B. and R. C. Harris. 1993. Review and assessment of methane emissions from wetlands. Chemosphere 26:261:320.

Bernal, B. and W. J. Mitsch. 2008. A comparison of soil carbon pools and profiles in wetlands in Costa Rica and Ohio. Ecological Engineering 34:311-323.

Bouchard, V., S. D. Frey, J. M. Gilbert, and S. E. Reed. 2007. Effects of macrophyte functional group richness on emergent freshwater wetland functions. Ecology 88:2903-2914.

Bridgham, S. D., J. P. Megonigal, J. K. Keller, N. B. Bliss, and C. Trettin. 2006. The carbon balance of North American wetlands. Wetlands 26:889-916.

Campbell, D. A., C. A. Cole, and R. P. Brooks. 2002. A comparison of natural and created wetlands in Pennsylvania, USA. Wetlands Ecology and Management 10:41-49.

Chen, H., S. P. Yao, N. Wu, Y. F. Wang, P. Luo, J. Q. Tian, Y. H. Gao, and G. Sun. 2008. Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications. Journal of Geophysical Research-Atmospheres 113: D12303, doi:10.1029/2006JD008072.

Cole, C. A. and D. Shafer. 2002. Section 404 wetland mitigation and permit success criteria in Pennsylvania, USA, 1986-1999. Environmental Management 30:508- 515.

Dahl, T. E. 1990. Wetland losses in the United States, 1789s to 1980s. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, USA.

109 Dahl, T. E. 2006. Status and trends of wetlands in the conterminous United States 1998 to 2004. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, USA.

Gogoi, N., K. Baruah, B. Gogoi, and P. K. Gupta. 2008. Methane emission from two different rice ecosystems (Ahu and Sali) at Lower Brahmaputra Valley zone of North East India. Applied Ecology and Environmental Research 6:99-112.

Gutrich, J. J., K. J. Taylor, and M. S. Fennessy. 2009. Restoration of vegetation communities of created depressional marshes in Ohio and Colorado (USA): the importance of initial effort for mitigation success. Ecological Engineering 35:351-368.

Harter, S. K. and W. J. Mitsch. 2003. Patterns of short-term sedimentation in a freshwater created marsh. Journal of Environmental Quality 32:325-334.

Healy, R. W., R. G. Striegl, T. F. Russell, G. L. Hutchinson, and G. P. Livingston. 1996. Numerical evaluation of static-chamber measurements of soil-atmosphere gas exchange: Identification of physical processes. Soil Science Society of America Journal 60:740-747.

Hernández, M. E. and W. J. Mitsch. 2006. Influence of hydrologic pulses, flooding frequency, and vegetation on nitrous oxide emissions from created riparian marshes. Wetlands 26:862-877.

Hernández, M. E. and W. J. Mitsch. 2007a. Denitrification potential and organic matter as affected by vegetation community, wetland age, and plant introduction in created wetlands. Journal of Environmental Quality 36:333-342.

Hernández, M. E. and W. J. Mitsch. 2007b. Denitrification in created riverine wetlands: Influence of hydrology and season. Ecological Engineering 30:78-88.

Hoeltje, S. M. and C. A. Cole. 2007. Losing function through wetland mitigation in Central Pennsylvania, USA. Environmental Management 39:385-402.

Holland, E. A., G. P. Robertson, J. Greenburg, P. M. Groffman, R. D. Boone, and J. R.

Gosz. 1999. Soil CO2, N2O, and CH4 exchange. p. 185-201. In G. P. Robertson, D. C. Coleman, and C.S. Bledsoe (eds.) Standard Soil Methods for Long-Term Ecological Research. Oxford University Press, New York, NY, USA.

Huang, G., X. Li, Y. Hu, Y. Shi, and D. Xiao. 2005. Methane (CH4) emission from a natural wetland of northern China. Journal of Environmental Science and Health 40:1227-1238.

110 Husin, Y. A., D. Murdiyarso, M. A. K. Khalil, R. A. Rasmussen, M. J. Shearer, S. Sabiham, A. Sunar, and H. Adijuwana. 1995. Methane flux from Indonesian wetland rice: the effects of water management and rice variety. Chemosphere 31:3153-3180.

Huttunen, J. T., H. Nykänen, J. Turunen, and P. J. Martikaninen. 2003. Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscanidia. Atmospheric Environment 37:147-151.

IPCC (Intergovernmental Panel on Climate Change). 2007. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Solomon S., D. Qin, M. Manning, Z. Chen, M Marquis, K.B. Averyt, M. Tignor, and H.L. Miller (eds.). Cambridge University Press, Cambridge, UK.

Kang, H., C. Freeman, D. Lee, and W. J. Mitsch. 1998. Enzyme activities in constructed wetlands: Implication for water quality amelioration. Hydrobiologia 368:231- 235.

Kim, J., S. B. Verma, D. P. Billesbach. 1999. Seasonal variation in methane emission from a temperate Phragmites-dominated marsh: effect of growth stage and plant- mediated transport. Global Change Biology 5:433-440.

Koch, O., D. Tscherko, and E. Kandeler. 2007. Seasonal and diurnal net methane emissions from organic soils of the Eastern Alps, Austria: effects of soil temperature, water balance, and plant biomass. Arctic, Antarctic, and Alpine Research 39:438-448.

Kettlewell, C. I., V. Bouchard, D. Porej, M. Micacchion, J. J. Mack, D. White, and L. Fay. 2008. An assessment of wetland impacts and compensatory mitigation in the Cuyahoga River Watershed, Ohio, USA. Wetlands 28:57-67.

King, G. M. 1996. In situ analyses of methane oxidation associated with the roots and rhizomes of a bur reed, Sparganium eurycarpum, in a Maine wetland. Applied and Environmental Microbiology 62:4548-4555.

Koh, H. S., C. A. Ochs, and K. W. Yu. 2009. Hydrologic gradient and vegetation

controls on CH4 and CO2 fluxes in a spring-fed forested wetland. Hydrobiologia 630: 271-286.

Krieger, K. A. 2003. Effectiveness of a coastal wetland in reducing pollution of a Laurentian Great Lake: hydrology, sediment, and nutrients. Wetlands 23:778- 791.

111 McCarthy, M. J., W. S. Gardner, P. J. Lavrentyev, K. M. Moats, F. J. Joehem, and D. M. Klarer. 2007. Effects of hydrological flow regime on sediment-water interface and water column nitrogen dynamics in a great lakes coastal wetland (Old Woman Creek, Lake Erie). Journal of Great Lakes Research 33:219-231.

Mishra, S., A. K. Rath, T. K. Adhya, V. R. Rao, and N. Sethunathan. 1997. Effect of continuous and alternate water regimes on methane efflux from rice under greenhouse conditions. Biology and Fertility of Soils 24:399-405.

Mitsch, W.J. and B.C. Reeder. 1991. Modelling nutrient retention of a freshwater coastal wetland: estimating the roles of primary productivity, sedimentation, resuspension and hydrology. Ecological Modelling 54:151-187.

Mitsch, W.J. and B.C. Reeder. 1992. Nutrient and hydrologic budgets of a Great Lakes coastal freshwater wetland during a drought year. Wetlands Ecology and Management 1:211-223.

Mitsch, W. J., X. Wu, R. W. Nairn, R. E. Weihe, N. Wang, R. Deal, and C. E. Boucher. 1998. Creating and restoring wetlands: A whole-ecosystem experiment in self- design. BioScience 48:1019-1030.

Mitsch, W. J., X. Wu, R. W. Nairn, and N. Wang. 2000. To plant or not to plant: response from Mitsch et al. BioScience 50:188-191.

Mitsch, W. J., N. Wang, L. Zhang, R. Deal, X. Wu, and A Zuwerink. 2005a. Using ecological indicators in a whole-ecosystem wetland experiment. pp. 211-235. In S. E. Jorgensen, F. L. Xu, and R. Costanza (eds.) Handbook of Ecological Indicators for Assessment of Ecosystem Health. CRC Press, Boca Raton, FL, USA.

Mitsch, W. J., L. Zhang, C. J. Anderson, A. E. Altor, and M. E. Hernández. 2005b. Creating riverine wetlands: Ecological succession, nutrient retention, and pulsing effects. Ecological Engineering 25:510-527.

Mitsch, W. J. and J. G. Gosselink. 2007. Wetlands, fourth edition. John Wiley & Sons, Inc., New York, NY, USA.

Mitsch, W. J., L. Zhang, D. F. Fink, M. E. Hernández, A. E. Altor, C. L. Tuttle, and A. M. Nahlik. 2008. Ecological Engineering of Floodplains. Ecohydrology & Hydrobiology 8:139-147.

Mitsch, W. J., J. G. Gosselink, C. J. Anderson, and L. Zhang. 2009. Wetland Ecosystems. John Wiley & Sons, Inc., New York, NY, USA.

112 Mitsch, W.J., A.M. Nahlik, P. Wolski, B. Bernal, L. Zhang, and L. Ramberg. in press. Tropical wetlands: Seasonal hydrologic pulsing, carbon sequestration, and methane emissions. Wetlands Ecology and Management.

Moore, T. R. and R. Knowles. 1990. Methane emissions from fen, bog and swamp peatlands in Quebec. Biogeochemistry 11:45-61.

Moovsavi, S. C., P. M. Crill, E. R. Pullman, D. W. Funk, and K. M. Peterson. 1996.

Controls on CH4 flux from an Alaskan boreal wetland. Global Biogeochemical Cycles 10:287-296.

Nahlik, A. M. and W. J. Mitsch. 2008. The effect of river pulsing on sedimentation in created riparian wetlands. Journal of Environmental Quality 37:1634-1643.

Nahlik, A. M. and W. J. Mitsch. In review. Effect of climate on methane emissions from tropical freshwater wetlands in Costa Rica. Global Change Biology.

Nairn, R. W. and W. J. Mitsch. 1999. Phosphorus removal in created wetland ponds receiving river overflow. Ecological Engineering 14:107-126.

Naser, H. M., O. Nagata, S. Tamura, and R. Hatano. 2007. Methane emissions from five paddy fields with different amounts of rice straw application in central Hokkaido, Japan. Soil Science and Plant Nutrition 53:95-101.

NRC (Committee on Wetland Mitigation; National Research Council). 2001. Compensating for Wetland Loss Under the Clean Water Act. National Academy Press, Washington, DC, USA.

Rask, H., J. Schoenau, and D. Anderson. 2002. Factors influencing methane flux form a boreal forest wetland in Saskatchewan, Canada. Soil Biology and Biochemistry 34:435-443.

Rath, A. K., B. Swain, B. Ramakrishnan, D. Panda, T. K. Adhya, V. R. Rao, and N. Sethunathan. 1999. Influence of fertilizer management and water regime on methane emission from rice fields. Agriculture, Ecosystems and Environment 76:99-107.

Robb, J. T. 2002. Assessing wetland compensatory mitigation sites to aid in establishing mitigation ratios. Wetlands 22:435-440.

Rose, C. and W. G. Crumpton. 2006. Spatial patterns in dissolved oxygen and methane concentrations in a prairie pothole wetland in Iowa, USA. Wetlands 26:1020- 1025.

113 Scott, J. T., M. J. McCarthy, W. S. Gardner, and R. D. Doyle. 2008. Denitrification, dissimilatory nitrate reduction to ammonium, and nitrogen fixation along a nitrate concentration gradient in a created freshwater wetland. Biogeochemistry 87:99- 111.

Shannon, R. D. and J. R. White. 1994. A three-year study of controls on methane emissions from two Michigan peatlands. Biogeochemistry 27:35-60.

Smemo, K. A. and J. B. Yavitt. 2006. A multi-year perspective on methane cycling in a shallow peat fen in central New York State, USA. Wetlands 26:20-29.

Spieles, D. J. and W. J. Mitsch. 2000a. The effects of season and hydrologic and chemical loading on nitrate retention in constructed wetlands: A comparison of low and high nutrient riverine systems. Ecological Engineering 14:77-91.

Spieles, D. J. and W. J. Mitsch. 2000b. Macroinvertebrate community structure in high- and low-nutrient constructed wetlands. Wetlands 20:716-729.

Tuttle, C. L, L. Zhang, and W. J. Mitsch. 2008. Aquatic metabolism as an indicator of the ecological effects of hydrologic pulsing in flow-through wetlands. Ecological Indicators 8:795-806.

Wang, B., Y. Xu, Z. Wang, Z. Li, Y. Guo, K. Shao, and Z. Chen. 1999. Methane emissions from rice fields as affected by organic amendment, water regime, crop establishment, and rice cultivar. Environmental Monitoring and Assessment 57:213-228.

Whalen, S. C. 2005. Biogeochemistry of methane exchange between natural wetlands and the atmosphere. Environmental Engineering Science 22:73-94.

Whalen, S. C. and W. S. Reeburgh. 2000. Methane oxidation, production, and emission at contrasting sites in a boreal bog. Geomicrobiology Journal 17:237-251.

Whiting, G. J., J. P. Chanton, D. S. Bartlett, and J. D. Happell. 1991. Relationships

between CH4 emission, biomass, and CO2 exchange in a subtropical grassland. Journal of Geophysical Research 96:13067-13071.

Whiting, G. J. and J. P. Chanton. 1993. Primary production control of methane emission from wetlands. Nature 364:794-795.

Whiting, G. J. and J. P. Chanton. 1996. Control of the diurnal pattern of methane emission from emergent aquatic macrophytes by gas transport mechanisms. Aquatic Botany 54:237-253.

114 Whiting, G. J. and J. P. Chanton. 2001. Greenhouse carbon balance of wetlands: methane emission versus carbon sequestration. Tellus 53B:521-528.

Whyte, R. S., D. Trexel-Kroll, D. M. Klarer, R. Shields, and D. A. Francko. 2008. The invasion and spread of Phragmites australis during a period of low water in a Lake Erie Coastal Wetland. Journal of Coastal Research 55:111-120.

Wilson, J. O., P. M. Crill, K. B. Bartlett, D. I. Sebacher, R. C. Harriss, and R. L. Sass. 1989. Seasonal variation of methane emissions from a temperate swamp. Biogeochemistry 8:55-71.

Wu, X. and W. J. Mitsch. 1998. Spatial and temporal patterns of algae in newly constructed freshwater wetlands. Wetlands 18:9-20.

Wuebbles, D. J. and K. Hayhoe. 2002. Atmospheric methane and global climate change. Earth-Science Reviews 57:177-210.

Zedler, J. B. 2004. Compensating for wetland losses in the United States. Ibis 146:92- 100.

115

-2 -1 Table 4.1. Comparison of mean annual methane emission rates (g CH4-C m y ) measured in this study to past studies in the same experimental wetlands and other temperate wetland studies. Different hydrologic regimes during the study periods are reported.

Table 4.2. Annual net primary productivity (g-dry wt m-2 y-1) and cumulative productivity (Mg ha-1) in the experimental wetland from 1997 to 2007.

116

Figure 4.1. Methane-sampling chamber site locations in Wetland 1 (planted) and Wetland 2 (self-colonizing) at the Olentangy River Wetland Research Park. Arrows indicate the inflows and outflows of the wetlands, with water moving from north to south. Light grey circles correspond to upland, dark grey circles correspond to shallow wetland, and black circles correspond to deep wetland chamber locations. Deepwater zones are designated by large ovals, and lines represent boardwalks.

117

Figure 4.2. Median (open circles) and mean (horizontal bars) of annual methane -2 -1 emissions (g CH4-C m y ) for planted Wetland 1 and self-colonizing Wetland 2. Methane emissions rates are reported next to the appropriate marker. Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between methane emissions of the same wetland.

118

Figure 4.3. Seasonal patterns of soil temperature (°C), chamber water level (cm), and -2 -1 methane emissions (mg CH4-C m h ) for each sampling period in planted Wetland 1 and self-colonizing Wetland 2. Error bars on mean soil temperatures represent S.E. Median methane emissions are designated by the solid marker, mean methane emissions are designated by the horizontal bar, and error bars represent the minimum and maximum methane emissions.

119

Figure 4.4. Median (open circles) and mean (horizontal bars) seasonal methane -2 -1 emissions (mg CH4-C m d ) for a) Wetland 1 and b) Wetland 2. Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between median seasonal methane emissions of the same wetland.

120

Figure 4.5. Relationship between methane emission rates and mean soil temperature for planted Wetland 1 (black dots), self-colonizing Wetland 2 (grey diamond), and natural wetland at Old Woman Creek (open square) for each sampling period. Solid, dotted, and dashed trend lines are for Wetland 1, Wetland 2, and Old Woman Creek, respectively. Boxes at 10°C demonstrate differences in methane emissions between wetlands at that temperature.

121

Figure 4.6. Median (open circles) and mean (horizontal bars) methane emissions (mg -2 -1 CH4-C m d ) for upland, shallow water, and deep water sampling sites in the created wetland sites (Wetlands 1 and 2 at the ORWRP) compared to a natural reference wetland (Old Woman Creek). Error bars represent the minimum and maximum methane emissions. Different letters indicate significant differences between methane emissions of the same wetland. 122

Figure 4.7. Estimated annual methane emission rates for experimental wetlands at the Olentangy River Wetland Research Park: a) emission rates for planted (Wetland 1) and self-colonizing wetland (Wetland 2) by year for 2004 to 2008 and b) relationship between methane emissions and cumulative macrophyte net primary productivity (Mg ha-1) for 2004 through 2007. Trend lines for a) represent each wetland and trend line for b) represents all points. 2004 and 2005 data are from Altor (2007) and Altor and Mitsch (2008). Cumulative productivity data are from Mitsch et al. (2009).

123

Figure 4.8. Estimated patterns of methane emission development in planted (black line) and self-colonized (grey line) created wetlands at the Olentangy River Wetland Research Park over time. Circular markers represent mean methane emissions from 2004-2007 are centered on year 12 for the planted wetland and the self-colonized wetland. Short bolded solid lines are the slope of methane emission over time from Figure 4.7a. Natural wetland emissions are based on those measured at Old Woman Creek wetland in Ohio and are assumed to be in steady state. The shaded area between the lines represents methane emissions that are potentially avoided by planting.

124

CHAPTER 5: CONCLUSIONS

This dissertation focused on water quality improvement in tropical treatment wetlands and methane emissions from natural tropical wetlands and created temperate wetlands. Conclusions have been generated that contribute to the fields of wetland ecology, biogeochemistry, and climate change. These conclusions are grouped by their associated project, water quality improvement and tropical treatment wetlands, methane emissions from natural tropical wetlands, and methane emissions from created temperate wetlands, and integrative conclusions across the dissertation as a whole are included at the end. Significant new findings are underlined.

5.1 Water quality improvement and tropical treatment wetlands

1. Tropical treatment wetlands can effectively remove nutrients from different

sources of wastewater; therefore, treatment wetlands are a viable and cost-

effective alternative to traditional wastewater treatment systems in the developing

tropics.

2. Warm temperatures in the tropics promote rapid growth of floating macrophytes,

which assimilate nutrients – this is one reason tropical treatment wetlands may be

so effective at removing pollutants from water. On the other hand, floating

125 macrophytes, typical of tropical treatment wetlands, also cause low dissolved

oxygen in the water column, partially offsetting nutrient removal.

3. Treatment wetland management practices, such as plant harvesting and dredging,

need to be thoroughly researched in regards to their implications on nutrient

removal and mosquito populations.

5.2 Methane emissions from natural tropical wetlands

4. The methane emission rates measured in tropical wetlands in this dissertation

were higher than many of the published tropical wetland methane emission

-2 -1 estimates. Methane emissions ranged from 175-500 g CH4-C m y in tropical

- wetlands in this study. The ranges reported in the literature are 1-800 g CH4-C m

2 y-1 for tropical wetlands, but most studies tend to estimate tropical wetland

-2 -1 emissions below 200 g CH4-C m y . It is likely that global tropical wetland

emissions have been underestimated in the past.

5. Tropical wetland methane emissions were highest in seasonally wet climates

compared to year-long wet climates.

6. Variability in methane emissions among natural wetlands in Costa Rica is high

due to climatic differences and different wetland physical characteristics.

Measuring methane emissions from a variety of types of wetlands in different

126 climates throughout the tropics is important in order to estimate global emission

rates.

7. Methane emission rates in the tropical wetlands studied were highest in mid-range

water levels of 30 to 50 cm, possibly because methane is oxidized in extremely

shallow water depths and in the water column in depths greater than 50 cm.

8. Our tropical methane studies suggest that methane emissions could increase in

tropical wetlands if either increased temperatures or more variable climatic

conditions occur in the future in the tropics.

5.3 Methane emissions from created temperate wetlands

9. Methane emissions from 13-year-old created wetlands were generally lower than

or comparable to methane emissions from natural wetlands.

10. As created wetlands develop over time and accumulate carbon in the soil,

methane emissions should be expected to increase for at least two decades.

11. Introducing wetland macrophytes at the time of wetland creation, as opposed to

allowing only self-colonization of more productive plants, seems to have resulted

in lower methane emissions, especially several years after planting. Planting

wetlands with desirable sedges and other non-clonal plants may be a good

management strategy for reducing methane emissions from created wetlands.

127

5.4 Integrative Conclusions

12. Methane emissions from wetlands are 85% higher in tropical climates than in

temperate climates, although there are exceptions to this generalization depending

on the specific physical characteristics of the wetland.

13. Even though wetlands create methane, they also provide ecosystem services such

as water quality improvement, carbon sequestration, flood mitigation, and habitat

development, all of which make these ecosystems valuable to humans and the

environment.

128

BIBLIOGRAPHY

Adhya, T.K., S.R. Mishra, A.K. Rath, K. Bharati, S.R. Mohanty, B. Ramakrishnan, V.R. Rao, and N. Sethunathan. 2000. Methane efflux from rice-based cropping systems under humid tropical conditions of eastern India. Agriculture, Ecosystems and Environment 79: 85-90.

Adrian, N.R., J.A. Robinson, and J.M. Suflita. 1994. Spatial variability in biodegradation rates as evidenced by methane production from an aquifer. Applied and Environmental Microbiology 60: 3632-3639.

Altor, A.E. and W.J. Mitsch. 2006. Methane flux from created riparian marshes: Relationship to intermittent versus continuous inundation and emergent macrophytes. Ecological Engineering 28: 224-234.

Altor, A.E. 2007. Methane and carbon dioxide fluxes in created riparian wetlands in the Midwestern USA: effects of hydrologic pulses, emergent vegetation and hydric soils. Ph.D. Dissertation. The Ohio State University, Columbus, OH, USA.

Altor, A.E. and W.J. Mitsch. 2008. Pulsing hydrology, methane emissions, and carbon dioxide fluxes in created marshes: a 2-year ecosystem study. Wetlands 28: 423- 438.

American Public Health Association, American Water Works Association, Water Environment Federation. 1998. Standard Methods for the Examination of Water and Wastewater, 20th edition, United Book Press, Inc., Baltimore, MD, USA.

Anderson, C.J., W.J. Mitsch, and R.W. Nairn. 2005. Temporal and spatial development of surface soil conditions at two created riverine marshes. Journal of Environmental Quality 34: 2072-2081.

Anderson, C.J. and W.J. Mitsch. 2006. Sediment, carbon, and nutrient accumulation at two 10-year-old created riverine marshes. Wetlands 26: 779-792.

Aselmann, I. and P.J. Crutzen. 1989. Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions. Journal of Atmospheric Chemistry 8: 307-358.

129

Austin, D. 2000. Final Report on the South Burlington, Vermont: Advanced Ecologically Engineered System (AEES) for Wastewater Treatment. Report to the Massachusetts Foundation for Excellence in Marine and Polymer Science, Inc.

Bachand, P.A.M. and A.J. Horne. 2000. Denitrification in constructed free-water surface wetlands. I. Effects of vegetation and temperature. Ecological Engineering 14: 17-32.

Banker, B.C., H.K. Hludze, D.P. Alford, R.D. DeLaune, and C.W. Lindau. 1995. Methane sources and sinks in rice paddy soils: relationship to emissions. Agriculture Ecosystems & Environment 53: 243-251.

Bartlett, K.B., P.M. Crill, D.I. Sebacher, R.C. Harriss, J.O. Wilson, and J.M. Melack. 1988. Methane flux from the central Amazonian floodplain. Journal of Geophysical Research 93: 1571-1582.

Bartlett, K.B., P.M. Crill, D.I. Sebacher, R.C. Harriss, J.O. Wilson, and J.M. Melack. 1988. Methane flux from the central Amazonian floodplain. Journal of Geophysical Research 93: 1571-1582.

Bartlett, K.B. and R.C. Harris. 1993. Review and assessment of methane emissions from wetlands. Chemosphere 26: 261:320.

Bergamaschi, P., C. Frankenberg, J.F. Meirink, M. Krol, F. Dentener, T. Wagner, U. Platt, J.O. Kaplan, S. Körner, M. Heimann, E.J. Dlugokencky, and A. Goede. 2007. Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations. Journal of Geophysical Research 112: D02304, doi:10.1029/2006JD007268.

Bernal, B. and W.J. Mitsch. 2008. A comparison of soil carbon pools and profiles in wetlands in Costa Rica and Ohio. Ecological Engineering 34: 311-323.

Billore, S.K., R. Bharadia, and A. Kumar. 1998. Potential removal of particulate matter and nitrogen through roots of water hyacinth in a tropical natural wetland. Current Science 74: 154-156.

Boon, P.I. and A. Mitchell 1995. Methanogenesis in the sediments of an Australian freshwater wetland: Comparison with aerobic decay, and factors controlling methanogenesis. FEMS Microbiology Ecology 18: 175-190.

Boon, P.I., A. Mitchell, and K. Lee. 1997. Effects of wetting and drying on methane emissions from ephemeral floodplain wetlands in south-eastern Australia. Hydrobiologia 357: 73-87.

130 Boon, P.I. and A. Mitchell. 1995. Methanogenesis in the sediments of an Australian freshwater wetland: Comparison with aerobic decay, and factors controlling methanogenesis. FEMS Microbiology Ecology 18: 175-190.

Bouchard, V., S. D. Frey, J. M. Gilbert, and S. E. Reed. 2007. Effects of macrophyte functional group richness on emergent freshwater wetland functions. Ecology 88: 2903-2914.

Bridgham, S.D., J.P. Megonigal, J.K. Keller, N.B. Bliss, and C. Trettin. 2006. The carbon balance of North American wetlands. Wetlands 26: 889-916.

Brix, H. and H.H. Schierup. 1989. The use of aquatic macrophytes in water-pollution control. Ambio 18: 100-107.

Campbell, D. A., C. A. Cole, and R. P. Brooks. 2002. A comparison of natural and created wetlands in Pennsylvania, USA. Wetlands Ecology and Management 10: 41-49.

Cao, M., K. Gregson, and S. Marshall. 1998. Global methane emission from wetlands and its sensitivity to climate change. Atmospheric Environment 12: 3291-3299.

Castillo-Muñoz, R. 1983. Geology. In: Janzen, D.H. (Ed.), Costa Rican Natural History. The University of Chicago Press, Chicago, USA, pp. 47-62.

Chen, H., N. Wu, Y.H. Gao, Y.F. Wang, P. Luo, and T.Q. Tian. 2009. Spatial variations on methane emissions from Zoige alpine wetlands of Southwest China. Science of the Total Environment 407: 1097-1104.

Chen, H., S.P. Yao, N. Wu, Y.F. Wang, P. Luo, J.Q. Tian, Y.H. Gao, and G. Sun. 2008. Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications. Journal of Geophysical Research-Atmospheres 113: D12303, doi:10.1029/2006JD008072.

Cole, C. A. and D. Shafer. 2002. Section 404 wetland mitigation and permit success criteria in Pennsylvania, USA, 1986-1999. Environmental Management 30: 508- 515.

Costa-Pierce, B.A. 1998. Preliminary investigation of an integrated aquaculture-wetland ecosystem using tertiary-treated municipal wastewater in Los Angeles County, California. Ecological Engineering 10: 341-354.

Cronk, J.K. 1996. Constructed wetlands to treat wastewater from dairy and swine operations: a review. Agriculture, Ecosystems & Environment 58: 97-114.

131 Crow, G.E. 2002. Aquatic Plants of Palo Verde National Park and the Tempisque River Valley. Instituto Nacional de Biodiversidad (INBio), Costa Rica.

Crozier, C.R., R.D. DeLaune, and W.J. Patrick Jr. 1995. Methane production in Mississippi deltaic plain wetland soils as a function of soil redox species. In: Lal, R., J. Kimble, E. Levine, and B.A. Stewart (Eds.), Soils and Global Climate Change, Lewis Publishers, Boca Raton, FL, USA, pp. 247-255.

Dahl, T.E. 1990. Wetland losses in the United States, 1789s to 1980s. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, USA.

Dahl, T.E. 2006. Status and trends of wetlands in the conterminous United States 1998 to 2004. U.S. Department of the Interior, Fish and Wildlife Service, Washington, DC, USA.

DeBusk, T.A. and K.R. Reddy. 1987. Wastewater treatment using floating aquatic macrophytes; contaminant removal processes and management strategies. In: Reddy, K.R. and W.H. Smith (Eds.), Aquatic Plants for Water Treatment and Resource Recovery. Magnolia Publishing, Inc., Orlando, FL, USA, pp. 643-656.

DeBusk, T.A., J.E. Peterson, and K.R. Reddy. 1995. Use of aquatic and terrestrial plants for removing phosphorus from dairy wastewaters. Ecological Engineering 5: 371-390.

DeBusk, T.A., K.A. Grace, F.E. Dierberg, S.D. Jackson, M.J. Chimney, and B. Gu. 2004. An investigation of the limits of phosphorus removal in wetlands: a mesocosm study of a shallow periphyton-dominated treatment system. Ecological Engineering 23: 1-14.

Denny, P. 1997. Implementation of constructed wetlands in developing countries. Water and Science Technology 35: 27-34.

Devol, A.H., J.E. Richey, W.A. Clark, and S.L. King. 1988. Methane emissions to the troposphere from the Amazon floodplain. Journal of Geophysical Research 93: 1583-1592.

Diemont, S.A.W. 2006. Mosquito larvae density and pollutant removal in tropical wetland treatment systems in Honduras. Environment International 32: 332-341.

Dierberg, F.E., J.J. Juston, T.A. DeBusk, K. Pietro, and B. Gu. 2005. Relationship between hydraulic efficiency and phosphorus removal in a submerged aquatic vegetation-dominated treatment wetland. Ecological Engineering 25: 9-23.

132 Drenner, R.W., D.J. Day, S.J. Basham, J.D. Smith, and S.I. Jensen. 1997. Ecological water treatment system for removal of phosphorus and nitrogen from polluted water. Ecological Applications 7: 381-390.

Ewel, K.C. 1997. Water quality improvement by wetlands. In: Daily G.C. (ed.), Nature’s Services: Societal Dependence on Natural Ecosystems. Island Press, Washington, DC, USA, pp. 329-344.

Figueres Olsen, J.M. 1995. Sustainable development: a challenge for Costa Rica. SAIS Review 16: 187-202.

Ford, P.W., P.I. Boon, and K. Lee. 2002. Methane and oxygen dynamics in a shallow floodplain lake: the significance of periodic stratification. Hydrobiologia 485: 97- 110.

Gambrell, R.P. and W.H. Patrick Jr. 1978. Chemical and microbiological properties of anaerobic soils and sediments. In: Hook, D.D. and R.M. Crawford (Eds.), Plant Life in Anaerobic Environments. Ann Arbor Science Publishers, Ann Arbor, MI, USA, pp. 375-423.

Gedney, N., P.M. Cox, and C. Huntingford. 2004. Climate feedback form wetland methane emission. Geophysical Research Letters 31: L20503, doi:10.1029/2004GL020919.

Gearhart, R.A., F. Klopp, and G. Allen. 1989. Constructed free surface wetland to treat and receive wastewater; pilot project to full scale. In: Hammer, D.A. (Ed.), Constructed Wetlands for Wastewater Treatment. Lewis Publishers, Chelsea, MI, USA, pp. 121-138.

Gilbert, B. and P. Frenzel. 1995. Methanotrophic bacteria in the rhizosphere of rice microcosms and their effect on porewater methane concentration and methane emission. Biology and Fertility of Soils 20: 93-100.

Gogoi, N., K. Baruah, B. Gogoi, and P.K. Gupta. 2008. Methane emission from two different rice ecosystems (Ahu and Sali) at Lower Brahmaputra Valley zone of North East India. Applied Ecology and Environmental Research 6: 99-112.

Greenway, M. 1997. Nutrient content of wetland plants in constructed wetland receiving municipal effluent in tropical Australia. Water Science and Technology 35: 135- 142.

Greenway, M. 2005. The role of constructed wetlands in secondary effluent treatment and water reuse in subtropical and arid Australia. Ecological Engineering 25: 501-509.

133 Greenway, M. and J.S. Simpson. 1996. Artificial wetlands for wastewater treatment, water reuse and wildlife in Queensland, Australia. Water Science and Technology 33: 221-229.

Greenway, M., P. Dale, and H. Chapman. 2003. An assessment of mosquito breeding and control in four surface flow wetlands in tropical–subtropical Australia. Water Science and Technology 48: 121-128.

Gutrich, J.J., K.J. Taylor, and M.S. Fennessy. 2009. Restoration of vegetation communities of created depressional marshes in Ohio and Colorado (USA): the importance of initial effort for mitigation success. Ecological Engineering 35: 351-368.

Harter, S.K. and W.J. Mitsch. 2003. Patterns of short-term sedimentation in a freshwater created marsh. Journal of Environmental Quality 32: 325-334.

Hadi, A., K. Inubushi, Y. Furukawa, E. Purnomo, M. Rasmadi, and H. Tsuruta. 2005. Greenhouse gas emissions from tropical peatlands of Kalimantan, Indonesia. Nutrient Cycling in Agroecosystems 71: 73-80.

Hammer, D.A. 1992. Designing constructed wetland systems to treat agricultural non- point source pollution. Ecological Engineering 1: 49-82.

Hamersley, M.R., B.L. Howes, D.S. White, S. Johnke, D. Young, S.B. Peterson, and J.M. Teal. 2001. Nitrogen balance and cycling in an ecologically engineered septage treatment system. Ecological Engineering 18: 61-75.

Healy, R.W., R.G. Striegl, T.F. Russell, G.L. Hutchinson, and G.P. Livingston. 1996. Numerical evaluation of static-chamber measurements of soil-atmosphere gas exchange: Identification of physical processes. Soil Science Society of America Journal 60: 740-747.

Hernández, M.E. and W.J. Mitsch. 2006. Influence of hydrologic pulses, flooding frequency, and vegetation on nitrous oxide emissions from created riparian marshes. Wetlands 26: 862-877.

Hernández, M.E. and W.J. Mitsch. 2007a. Denitrification potential and organic matter as affected by vegetation community, wetland age, and plant introduction in created wetlands. Journal of Environmental Quality 36: 333-342.

Hernández, M.E. and W.J. Mitsch. 2007b. Denitrification in created riverine wetlands: Influence of hydrology and season. Ecological Engineering 30: 78-88.

Hoeltje, S. M. and C. A. Cole. 2007. Losing function through wetland mitigation in Central Pennsylvania, USA. Environmental Management 39: 385-402.

134

Holland, E.A., G.P. Robertson, J. Greenburg, P.M. Groffman, R.D. Boone, and J.R.

Gosz. 1999. Soil CO2, N2O, and CH4 exchange. p. 185-201. In G. P. Robertson, D. C. Coleman, and C.S. Bledsoe (eds.) Standard Soil Methods for Long-Term Ecological Research. Oxford University Press, New York, NY, USA.

Huang, G., X. Li, Y. Hu, Y. Shi, and D. Xiao. 2005. Methane (CH4) emission from a natural wetland of northern China. Journal of Environmental Science and Health 40: 1227-1238.

Husin, Y.A., D. Murdiyarso, M.A.K. Khalil, R.A. Rasmussen, M.J. Shearer, S. Sabiham, A. Sunar, and H. Adijuwana. 1995. Methane flux from Indonesian wetland rice: the effects of water management and rice variety. Chemosphere 31: 3153-3180.

Huttunen, J.T., H. Nykänen, J. Turunen, and P.J. Martikaninen. 2003. Methane emissions from natural peatlands in the northern boreal zone in Finland, Fennoscanidia. Atmospheric Environment 37: 147-151.

IPCC (Intergovernmental Panel on Climate Change). 2007. In: Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. Averyt, M. Tignor, and H.L. Miller (Eds.), Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, 996 pp.

IPCC (Intergovernmental Panel on Climate Change). 2008. In: Bates, B.C., Z.W. Kundzewicz, S. Wu, and J.P. Palutikof (Eds.), Climate Change and Water, Technical Paper, IPCC Secretariat, Geneva, 210 pp.

Kadlec, R.H. and R.L. Knight. 1996. Treatment Wetlands. Lewis Publishers, Boca Raton, FL, USA.

Kadlec, R.H. and S. Wallace. 2009. Treatment Wetlands, 2nd edition. CRC Press, Boca Raton, FL, USA.

Kang, H. and C. Freeman. 2002. The influence of hydrochemistry on methane emissions from two contrasting northern wetlands. Air, Water, and Soil Pollution 141: 263- 272.

Kang, H., C. Freeman, D. Lee, and W.J. Mitsch. 1998. Enzyme activities in constructed wetlands: Implication for water quality amelioration. Hydrobiologia 368: 231- 235.

Kantawanichkul, S., S. Pilaila, W. Tanapiyawanich, W. Tikampornpittaya, and S. Kamkrua. 1999. Wastewater treatment by tropical plants in vertical-flow constructed wetlands. Water Science Technology 40: 173-178. 135

Kantawanichkul, S., S. Kladprasert, and H. Brix. 2009. Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus. Ecological Engineering 35: 238-247.

Kettlewell, C.I., V. Bouchard, D. Porej, M. Micacchion, J.J. Mack, D. White, and L. Fay. 2008. An assessment of wetland impacts and compensatory mitigation in the Cuyahoga River Watershed, Ohio, USA. Wetlands 28: 57-67.

Kim, J., S.B. Verma, D.P. Billesbach. 1999. Seasonal variation in methane emission from a temperate Phragmites-dominated marsh: effect of growth stage and plant- mediated transport. Global Change Biology 5: 433-440.

Kim, J., S.B. Verma, and D.P. Billesbach 1998. Seasonal variation in methane emission form a temperate Phragmites-dominated marsh: effect of growth stage and plant- mediated transport. Global Change Biology 5: 433-440.

King, D.A. 1996. Allometry and life history of tropical trees. Journal of Tropical Ecology 12: 25-44.

King, G.M. 1996. In situ analyses of methane oxidation associated with the roots and rhizomes of a bur reed, Sparganium eurycarpum, in a Maine wetland. Applied and Environmental Microbiology 62: 4548-4555.

Knight, R.L. 1990. Wetland systems. In: Natural Systems for Wastewater Treatment. Manual of Practice FD-16. Water Pollution Control Federation, Alexandria, VA, USA, pp. 211-260.

Knight, R.L., V.W.E. Payne Jr., R.E. Borer, R.A. Clarke Jr., and J.H. Pries. 2000. Constructed wetlands for livestock wastewater management. Ecological Engineering 15: 41-55.

Koch, O., D. Tscherko, and E. Kandeler. 2007. Seasonal and diurnal net methane emissions from organic soils of the Eastern Alps, Austria: effects of soil temperature, water balance, and plant biomass. Arctic, Antarctic, and Alpine Research 39: 438-448.

Koh, H.S., C.A. Ochs, and K.W. Yu. 2009. Hydrologic gradient and vegetation controls

on CH4 and CO2 fluxes in a spring-fed forested wetland. Hydrobiologia 630: 271- 286.

Koottatep, T. and C. Polrasert. 1997. Role of plant uptake on nitrogen removal in constructed wetlands located in the tropics. Water Science Technology 36: 1-8.

136 Krieger, K.A. 2003. Effectiveness of a coastal wetland in reducing pollution of a Laurentian Great Lake: hydrology, sediment, and nutrients. Wetlands 23: 778- 791.

Lin, Y., S. Jing, T. Wang, and D. Lee. 2002. Effects of macrophytes and external carbon sources on nitrate removal from groundwater in constructed wetlands. Environmental Pollution 119: 413-420.

Ma, S. and J. Yan. 1989. Ecological engineering for treatment and utilization of wastewater. In: Mitsch, W.J. and S.E. Jørgensen (Eds.), Ecological Engineering, An Introduction to Ecotechnology. John Wiley & Sons, Inc., New York, NY, USA, pp. 185-217.

Maine, M.A., N. Suñe, H. Hadad, G. Sánchez, and C. Bonetto. 2009. Influence of vegetation on the removal of heavy metals and nutrients in a constructed wetland. Journal of Environmental Management 90: 355-363.

Matthews, E. and I. Fung. 1987. Methane emission from natural wetlands: Global distribution, area, and environmental characteristics of sources. Global Biogeochemistry Cycles 1: 61-86.

McCarthy, M.J., W.S. Gardner, P.J. Lavrentyev, K.M. Moats, F.J. Joehem, and D.M. Klarer. 2007. Effects of hydrological flow regime on sediment-water interface and water column nitrogen dynamics in a great lakes coastal wetland (Old Woman Creek, Lake Erie). Journal of Great Lakes Research 33: 219-231.

McCoy, M. and J.M. Rodríguez. 1994. Cattail (Typha dominguesis) eradication methods in the restoration of a tropical, seasonal, freshwater marsh. In: Mitsch, W.J. (ed.), Global Wetlands: Old World and New, Elsevier Publishing Company, Amsterdam, pp. 469-482.

Melack, J.M., L.L. Hess, M. Gastil, B.R. Forsberg, S.K. Hamilton, I.B.T. Lima, and E.M.L.M. Novo. 2004. Regionalization of methane emissions in the Amazon Basin with microwave remote sensing. Global Change Biology 10: 530-544.

Mishra, S., A.K. Rath, T.K. Adhya, V.R. Rao, and N. Sethunathan. 1997. Effect of continuous and alternate water regimes on methane efflux from rice under greenhouse conditions. Biology and Fertility of Soils 24: 399-405.

Mitsch, W.J. 1977. Water hyacinth (Eichhornia crassipes) nutrient uptake and metabolism in a north-central Florida marsh. Archiv fuer Hydrobiologie 81: 188- 210.

137 Mitsch, W.J. 1995. Restoration of our lakes and rivers with wetlands – an important application of ecological engineering. Water Science and Technology 31: 167- 177.

Mitsch, W.J. and B.C. Reeder. 1991. Modelling nutrient retention of a freshwater coastal wetland: estimating the roles of primary productivity, sedimentation, resuspension and hydrology. Ecological Modelling 54: 151-187.

Mitsch, W.J. and B.C. Reeder. 1992. Nutrient and hydrologic budgets of a Great Lakes coastal freshwater wetland during a drought year. Wetlands Ecology and Management 1: 211-223.

Mitsch, W.J. and X. Wu. 1995. Wetlands and global change. In, R. Lal, J. Kimble, E. Levine, and B.A. Stewart (Eds.), Advances in Soil Science, Soil Management and Greenhouse Effect. Lewis Publishers, Boca Raton, FL, USA. pp. 205-230.

Mitsch, W.J., X. Wu, R.W. Nairn, R.E. Weihe, N. Wang, R. Deal, and C.E. Boucher. 1998. Creating and restoring wetlands: A whole-ecosystem experiment in self- design. BioScience 48: 1019-1030.

Mitsch, W.J. and J.G. Gosselink. 2000. Wetlands, 3rd edition. John Wiley & Sons, Inc., New York, NY, USA.

Mitsch, W.J., X. Wu, R.W. Nairn, and N. Wang. 2000. To plant or not to plant: response from Mitsch et al. BioScience 50: 188-191.

Mitsch, W.J., A.J. Horne, and R.W. Nairn. 2000. Nitrogen and phosphorus retention in wetlands - ecological approaches to solving excess nutrient problems. Ecological Engineering 14: 1-7.

Mitsch, W.J. and S.E. Jørgensen. 2004. Ecological Engineering and Ecosystem Restoration. John Wiley & Sons, Inc., Hoboken, NJ, USA.

Mitsch, W.J., N. Wang, L. Zhang, R. Deal, X. Wu, and A. Zuwerink. 2005a. Using ecological indicators in a whole-ecosystem wetland experiment. pp. 211-235. In S. E. Jorgensen, F. L. Xu, and R. Costanza (eds.) Handbook of Ecological Indicators for Assessment of Ecosystem Health. CRC Press, Boca Raton, FL, USA.

Mitsch, W.J., L. Zhang, C.J. Anderson, A.E. Altor, and M.E. Hernández. 2005b. Creating riverine wetlands: Ecological succession, nutrient retention, and pulsing effects. Ecological Engineering 25: 510-527.

Mitsch, W.J. and J.G. Gosselink. 2007. Wetlands, 4th edition. John Wiley & Sons, Inc., New York, NY, USA.

138

Mitsch, W.J., J. Tejada, A.M. Nahlik, B. Kohlmann, B. Bernal, and C.E. Hernández. 2008. Tropical wetlands for climate change research, water quality management and conservation education on a university campus in Costa Rica. Ecological Engineering 34: 276-288.

Mitsch, W.J., L. Zhang, D.F. Fink, M.E. Hernández, A.E. Altor, C.L. Tuttle, and A.M. Nahlik. 2008. Ecological Engineering of Floodplains. Ecohydrology & Hydrobiology 8: 139-147.

Mitsch, W.J., J.G. Gosselink, C.J. Anderson, and L. Zhang. 2009. Wetland Ecosystems. John Wiley & Sons, Inc., New York, NY, USA.

Mitsch, W.J., A.M. Nahlik, P. Wolski, B. Bernal, L. Zhang, and L. Ramberg. in press. Tropical wetlands: Seasonal hydrologic pulsing, carbon sequestration, and methane emissions. Wetlands Ecology and Management.

Moore, T.R. and R. Knowles. 1990. Methane emissions from fen, bog and swamp peatlands in Quebec. Biogeochemistry 11: 45-61.

Moore, T.R. and N.T. Roulet. 1995. Methane emissions from Canadian peatlands. In: Lal, R., J. Kimble, E. Levine, and B.A. Stewart (Eds.), Advances in Soil Science: Soils and Global Change. CRC Press, Boca Raton, FL, USA pp. 153-164.

Moovsavi, S.C., P.M. Crill, E.R. Pullman, D.W. Funk, and K.M. Peterson. 1996.

Controls on CH4 flux from an Alaskan boreal wetland. Global Biogeochemical Cycles 10: 287-296.

Nahlik, A.M. and W.J. Mitsch. 2008. The effect of river pulsing on sedimentation in created riparian wetlands. Journal of Environmental Quality 37: 1634-1643.

Nahlik, A.M. and W.J. Mitsch. In review. Effect of climate on methane emissions from tropical freshwater wetlands in Costa Rica. Global Change Biology.

Nairn, R.W. and W.J. Mitsch. 1999. Phosphorus removal in created wetland ponds receiving river overflow. Ecological Engineering 14: 107-126.

Naser, H.M., O. Nagata, S. Tamura, and R. Hatano. 2007. Methane emissions from five paddy fields with different amounts of rice straw application in central Hokkaido, Japan. Soil Science and Plant Nutrition 53: 95-101.

NRC (Committee on Wetland Mitigation; National Research Council). 2001. Compensating for Wetland Loss Under the Clean Water Act. National Academy Press, Washington, DC, USA.

139 Nzengy’a, D.M. and B.E.L. Wishitemi. 2001. The performance of constructed wetlands for wastewater treatment: a case study of Splash wetland in Nairobi, Kenya. Hydrological Processes 15: 3239-3247.

Odum, E.P. 1971. Fundamentals of Ecology, 3rd edition. WB Saunders Co, Philadelphia, PA, USA.

Okurut, T.O., G.B.J. Rijs, and J.J.A. van Bruggen. 1999. Design and performance of experimental constructed wetlands in Uganda, planted with Cyperus papyrus and Phragmites mauritianus. Water Science and Technology 40: 265-271.

Peterson, S.B. and T.M. Teal. 1996. The role of plants in ecologically engineered wastewater treatment systems. Ecological Engineering 6: 137-148.

Postel, S. and S. Carpenter. 1997. Freshwater ecosystem services. In: Daily, G.C. (Ed.), Nature’s Services: Societal Dependence on Natural Ecosystems. Island Press, Washington, DC, USA. pp. 195-214.

Rask, H., J. Schoenau, and D. Anderson. 2002. Factors influencing methane flux form a boreal forest wetland in Saskatchewan, Canada. Soil Biology and Biochemistry 34: 435-443.

Rath, A.K., B. Swain, B. Ramakrishnan, D. Panda, T. K. Adhya, V. R. Rao, and N. Sethunathan. 1999. Influence of fertilizer management and water regime on methane emission from rice fields. Agriculture, Ecosystems and Environment 76: 99-107.

Reed, S.C., R.W. Crites, and E.J. Middlebrooks. 1995. Natural Systems for Waste Management and Treatment, 2nd edition. McGraw-Hill, New York, NY, USA.

Reilly, J.F., A.J. Horne, and C.D. Miller. 2000. Nitrate removal from a drinking water supply with large free-surface constructed wetlands prior to groundwater recharge. Ecological Engineering 14: 33-47.

Robb, J.T. 2002. Assessing wetland compensatory mitigation sites to aid in establishing mitigation ratios. Wetlands 22: 435-440.

Rose, C. and W.G. Crumpton. 2006. Spatial patterns in dissolved oxygen and methane concentrations in a prairie pothole wetland in Iowa, USA. Wetlands 26: 1020- 1025.

Roulet, R., T. Ash, and T.R. Moore. 1992. Low boreal wetlands as a source of atmospheric methane. Journal of Geophysical Research 97: 3739-3749.

140 Sartoris, J.J., J.S. Thullen, L.B. Barber, and D.E. Salas. 2000. Investigation of nitrogen transformations in a southern California constructed wastewater treatment wetland. Ecological Engineering 14: 49-65.

Scott, J.T., M.J. McCarthy, W.S. Gardner, and R.D. Doyle. 2008. Denitrification, dissimilatory nitrate reduction to ammonium, and nitrogen fixation along a nitrate concentration gradient in a created freshwater wetland. Biogeochemistry 87: 99- 111.

Segers, R. 1998. Methane production and methane consumption: a review of processes underlying wetland methane fluxes. Biogeochemistry 41: 23-51.

Shannon, R.D. and J.R. White. 1994. A three-year study of controls on methane emissions from two Michigan peatlands. Biogeochemistry 27: 35-60.

Shelford, V.E. 1912. Ecological succession. V. Aspects of physiological classification. Biological Bulletin 23: 331-370.

Shindell, D.T., B.P. Walter, and G. Faluvegi. 2004. Impacts of climate change on methane emissions from wetlands. Geophysical Research Letters 31: L21202, doi:10.1029/2004GL021009.

Shutes, R.B.E. 2001. Artificial wetlands and water quality improvement. Environmental International 26: 441-447.

Singh, S., J.S. Singh, and A.K. Kashyap. 1999. Methane flux from irrigated rice fields in relation to crop growth and N-fertilization. Soil Biology and Biochemistry 31: 1219-1228.

Singh, S.N., K. Kulshreshtha, and S. Agnihotri. 2000. Seasonal dynamics of methane emission from wetlands. Chemosphere: Global Change Science 2: 39-46.

Smemo, K.A. and J.B. Yavitt. 2006. A multi-year perspective on methane cycling in a shallow peat fen in central New York State, USA. Wetlands 26: 20-29.

Smith, L.K., W.M. Lewis Jr., J.P. Chanton, G. Cronin, and S.K. Hamilton. 2000. Methane emissions from the Orinoco River floodplain, Venezuela. Biogeochemistry 51: 113-140.

Snyder, J.M. 2002. Methane emissions from the tropical Atawapaskat wetlands. Journal of Atawapaskat Research 1: 001-007.

Solano, M.L., P. Soriano, and M.P. Ciria. 2004. Constructed wetlands as a solution for wastewater treatment in small villages. Biosystems Engineering 87: 109-118.

141 Sollins, P., M.F. Sancho, Ch.R. Mata, and R.L. Sanford Jr. 1994. Soil and soil process research. In: McDade, L.A., K.S. Bawa, H.A. Hespenheide, and G.S. Hartshorn (Eds.), La Selva: Ecology and Natural History of a Neotropical Rainforest. University of Chicago Press, Chicago, pp. 34-63.

Song, C.C., X.F. Xu, H.Q. Tian, and Y.Y. Wang. 2009. Ecosystem-atmosphere

exchange of CH4 and N2O and ecosystem respiration in wetlands in the Sanjiang Plain, Northeastern China. Global Change Biology 15: 692-705.

Sooknah, R.D. and A.C. Wilkie. 2004. Nutrient removal by floating aquatic macrophytes cultured in anaerobically flushed dairy manure wastewater. Ecological Engineering 22: 27-42.

Spieles, D.J. and W.J. Mitsch. 2000a. The effects of season and hydrologic and chemical loading on nitrate retention in constructed wetlands: A comparison of low and high nutrient riverine systems. Ecological Engineering 14: 77-91.

Spieles, D.J. and W.J. Mitsch. 2000b. Macroinvertebrate community structure in high- and low-nutrient constructed wetlands. Wetlands 20: 716-729.

Stein, H., M. Springer, and B. Kohlmann. In press. Comparison of two sampling methods for biomonitoring using aquatic macroinvertebrates in the Dos Novillos River, Costa Rica. Ecological Engineering.

Stone, K.C., M.E. Poach, P.G. Hunt, and G.B. Reddy. 2004. Marsh-pond-marsh constructed wetland design analysis for swine lagoon wastewater treatment. Ecological Engineering 23: 127-133.

Thullen, J.S., J.J. Sartoris, and W.E. Walton. 2002. Effects of vegetation management in constructed wetland treatment cells on water quality and mosquito production. Ecological Engineering 18: 441-457.

Thullen, J.S., J.J. Sartoris, and S.M. Nelson. 2005. Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance. Ecological Engineering 25: 583-593.

Todd, J., E.J.G. Brown, and E. Wells. 2003. Ecological design applied. Ecological Engineering 20: 412-440.

Tokida, T., T. Miyazaki, M. Mizogughi, and M. Seki. 2005. In situ accumulation of methane bubbles in a natural wetland soil. European Journal of Soil Science 56: 389-395.

142 Tuttle, C.L, L. Zhang, and W.J. Mitsch. 2008. Aquatic metabolism as an indicator of the ecological effects of hydrologic pulsing in flow-through wetlands. Ecological Indicators 8: 795-806.

Van der Gon, H.A.C.D. and H.U. Neue. 1995. Influence of organic matter incorporation on the methane emission from a wetland rice field. Global Biogeochemical Cycles 9: 11-22.

Vásquez Morera, A. 1983. Soils. In: Janzen, D.H. (Ed.), Costa Rican Natural History. The University of Chicago Press, Chicago, USA, pp. 63-65.

Verhoeven, J.T.A. and A.F.M. Mueleman. 1999. Wetlands for wastewater treatment: opportunities and limitations. Ecological Engineering 12: 5-12.

Vymazal, J., H. Brix, P.F. Cooper, R. Haberl, R. Perfler, and J. Laber. 1998. Removal mechanisms and types of constructed wetlands. In: Vymazal, J., H. Brix, P.F. Cooper, M.B. Green, and R. Haberl (Eds.), Constructed Wetlands for Wastewater Treatment in Europe. Backhuys Publishers, Leiden, The Netherlands, pp. 17-66.

Wachinger, G., S. Fiedler, K. Zepp, A. Gattinger, M. Sommer, and K. Roth. 2000. Variability of soil methane production on the micro-scale: spatial associate with hot spots of organic material and Archaeal populations. Soil Biology & Biochemistry 32: 1121-1130.

Waddington, J.M., N.T. Roulet, and R.V. Swanson. 1996. Water table control of CH4 emission enhancement by vascular plants in boreal peatlands. Journal of Geophysical Research 101: 22775-22785.

Walton, W.E. and P.D. Workman. 1998. Effect of marsh design on the abundance of mosquitoes in experimental constructed wetlands in southern California. Journal of the American Mosquito Control Association 14: 95-107.

Wang, B., H.U. Neue, and H.P. Samonte. 1997. The effect of controlled soil

temperature on diel CH4 emission variation. Chemosphere 35: 2083-2092.

Wang, B., Y. Xu, Z. Wang, Z. Li, Y. Guo, K. Shao, and Z. Chen. 1999. Methane emissions from rice fields as affected by organic amendment, water regime, crop establishment, and rice cultivar. Environmental Monitoring and Assessment 57: 213-228.

Weinberg, S. 2004. The Central America Free Trade Agreement: Three Reasons for Congress to Vote No, Comments to a Congressional Briefing on CAFTA, Oxfam America Policy Advisor, January 22, 2004.

143 Whalen, S.C. and W.S. Reeburgh. 2000. Methane oxidation, production, and emission at contrasting sites in a boreal bog. Geomicrobiology Journal 17: 237-251.

Whalen, S.C. 2005. Biogeochemistry of methane exchange between natural wetlands and the atmosphere. Environmental Engineering Science 22: 73-94.

Whigham, D.F. and T.E. Jordan. 2003. Isolated wetlands and water quality. Wetlands 23: 541-549.

Whiting, G.J., J.P. Chanton, D.S. Bartlett, and J.D. Happell. 1991. Relationships

between CH4 emission, biomass, and CO2 exchange in a subtropical grassland. Journal of Geophysical Research 96: 13067-13071.

Whiting, G.J. and J.P. Chanton. 1993. Primary production control of methane emission from wetlands. Nature 364: 794-795.

Whiting, G.J. and J.P. Chanton. 1996. Control of the diurnal pattern of methane emission from emergent aquatic macrophytes by gas transport mechanisms. Aquatic Botany 54: 237-253.

Whiting, G.J. and J.P. Chanton. 2001. Greenhouse carbon balance of wetlands: methane emission versus carbon sequestration. Tellus 53B: 521-528.

Whyte, R.S., D. Trexel-Kroll, D.M. Klarer, R. Shields, and D.A. Francko. 2008. The invasion and spread of Phragmites australis during a period of low water in a Lake Erie Coastal Wetland. Journal of Coastal Research 55: 111-120.

Wilson, J.O., P.M. Crill, K.B. Bartlett, D.I. Sebacher, R.C. Harriss, and R.L. Sass. 1989. Seasonal variation of methane emissions from a temperate swamp. Biogeochemistry 8: 55-71.

Wu, X. and W.J. Mitsch. 1998. Spatial and temporal patterns of algae in newly constructed freshwater wetlands. Wetlands 18: 9-20.

Wuebbles, D.J. and K. Hayhoe. 2002. Atmospheric methane and global climate change. Earth-Science Reviews 57: 177-210.

Yavitt, J.B. 1997. Methane and carbon dioxide dynamics in Typha latifolia (L.) wetlands in central New York state. Wetlands 17: 394-406.

Yu, K.W., Z.P. Wang, A. Vermoesen, W.H. Patrick Jr., and O. Van Cleemput. 2001. Nitrous oxide and methane emissions from different soil suspensions: effect of soil redox status. Biology and Fertility of Soils 34: 25-30.

144 Yu, K., S.P. Faulkner, and M.J. Baldwin. 2008. Effect of hydrological conditions on nitrous oxide, methane, and carbon dioxide dynamics in a bottomland hardwood forest and its implication for soil carbon sequestration. Global Change Biology 14: 798-812.

Zedler, J.B. 2004. Compensating for wetland losses in the United States. Ibis 146: 92- 100.

145

Appendix A: Raw Laboratory Data from Tropical Treatment Wetlands in Costa Rica

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) Lecheria I-B3 15-Aug-08 * 8.10 35.155 0.12 1.50 * 1720 * Lecheria O 15-Aug-08 * 7.40 3.537 0.43 0.66 * 445 * Lecheria I 15-Aug-08 * 7.70 5.335 1.45 0.58 * 245 * Lecheria O 15-Aug-08 * 7.60 * 0.33 0.26 * 770 * Lecheria I-A 15-Aug-08 * 7.80 3.718 0.15 0.24 * 395 * Lecheria O 15-Aug-08 * 7.60 * 1.31 0.40 * 160 * Lecheria I 15-Aug-08 * 7.50 2.129 * 0.12 * 70 * Lecheria O 15-Aug-08 * 7.80 0.767 0.14 0.30 * 245 * Sanitario I-A2 15-Aug-08 * 7.60 0.054 0.45 0.04 * 245 * Sanitario O 15-Aug-08 * 6.80 5.574 0.05 0.26 * 245 * LaPA I-A 15-Aug-08 * 7.00 1.773 0.15 0.30 * 1545 * LaPA O 15-Aug-08 * 7.30 5.423 0.03 0.70 * 45 * LaPA R 15-Aug-08 * 7.50 4.212 0.34 0.24 * 52 * Papel I-B 15-Aug-08 * 7.50 4.153 1.09 0.21 * 995 * Papel O 15-Aug-08 * 7.00 8.420 0.46 0.36 * 5420 * Empacadora S-B 18-Aug-08 * 7.90 5.495 1.93 0.40 * 2070 * Empacadora S-C 18-Aug-08 * 7.20 0.319 2.89 0.20 * 3495 * Empacadora S-D 18-Aug-08 * 7.40 0.415 1.31 0.14 * 570 * Empacadora S-E 18-Aug-08 * 7.40 4.803 2.00 0.44 * 670 * Empacadora S-F 18-Aug-08 * 7.60 0.486 1.28 0.32 * 3520 * Empacadora R 18-Aug-08 * * * * * * * * Biodigestor I 5-Sep-08 * 7.00 3.529 * 1.08 * 1645 * Biodigestor O 5-Sep-08 * 7.20 38.759 0.10 9.02 * 1545 * Biodigestor O 5-Sep-08 * 7.20 36.412 0.76 1.87 * 1145 * Canal O 5-Sep-08 * 7.40 38.391 0.21 9.28 * 545 * Canal I 5-Sep-08 * 7.20 37.452 0.32 1.34 * 270 * Canal O 5-Sep-08 * 7.80 41.442 0.49 5.38 * 270 * Canal I 5-Sep-08 * 7.70 39.329 0.44 5.00 * 120 * Canal O 5-Sep-08 * 7.60 36.982 0.74 4.70 * 245 * Canal I 5-Sep-08 * 7.70 38.994 0.48 3.18 * 2245 * Canal O 5-Sep-08 * 7.90 38.491 0.19 5.26 * 270 * Canal I 5-Sep-08 * 8.00 47.678 0.05 9.48 * 770 * Canal O 5-Sep-08 * 7.60 38.424 1.30 4.80 * 245 * Canal I 5-Sep-08 * 7.70 39.765 0.23 9.88 * 1845 * Canal O 5-Sep-08 * 7.90 26.115 0.25 9.62 * 195 *

Table A1. Nutrients, oxygen-demanding substances, and solids estimated from tropical treatment wetlands in Costa Rica. 146 Table A1 continued

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) Sanitario O 26-Nov-08 9:30 5.49 3.301 0.26 0.00 22.0 0 3.9 Biodigestor I 26-Nov-08 10:15 6.60 9.190 0.21 2.86 17.0 47 8.3 Biodigestor O 26-Nov-08 10:20 5.85 78.697 0.24 4.20 17.0 75 31.0 Canal O 26-Nov-08 10:25 7.00 78.697 0.98 4.06 117.0 0 18.0 Canal I 26-Nov-08 10:30 7.00 75.528 0.47 3.70 60.5 27 17.0 Canal O 26-Nov-08 10:32 7.39 70.951 0.64 4.68 54.5 67 13.6 Canal I 26-Nov-08 10:36 7.33 65.669 0.78 4.68 23.5 2 133.0 Canal O 26-Nov-08 10:40 7.65 79.049 0.91 4.70 80.0 77 9.2 Canal I 26-Nov-08 10:42 7.71 73.768 1.30 4.76 42.0 37 9.3 Canal O 26-Nov-08 10:45 7.73 65.669 1.99 2.72 29.0 2 8.4 Canal I 26-Nov-08 10:51 7.81 59.683 1.38 3.18 38.0 0 9.6 Canal O 26-Nov-08 10:55 7.72 64.613 2.42 3.52 67.3 152 6.0 Canal I 26-Nov-08 10:57 7.75 57.570 2.22 3.66 19.3 55 6.2 Canal O 26-Nov-08 11:00 7.66 44.894 2.84 3.46 28.7 122 5.5 Lecheria I-B2 26-Nov-08 13:40 6.55 7.077 0.40 0.82 22.0 422 112.0 Lecheria I-B3 26-Nov-08 13:43 6.72 4.120 0.33 0.51 61.0 125 93.0 Lecheria I-B1 26-Nov-08 13:45 6.43 12.993 0.09 0.52 53.5 237 38.0 Lecheria I-B4 26-Nov-08 13:48 6.50 1.188 * 0.63 82.0 115 85.0 Lecheria I-A 26-Nov-08 13:52 6.41 12.923 2.04 1.84 20.7 0 12.7 Lecheria O 26-Nov-08 13:57 6.38 9.542 0.07 0.06 100.0 0 7.9 Lecheria I 26-Nov-08 14:00 6.14 0.555 0.15 0.13 52.0 27 18.6 Lecheria O 26-Nov-08 14:03 5.92 1.646 * 0.06 12.3 0 21.0 Lecheria I-A 26-Nov-08 14:30 5.85 2.491 * 0.02 26.3 17 5.4 Lecheria I-B 26-Nov-08 14:35 6.08 1.294 * 0.02 21.7 0 8.5 Lecheria O 26-Nov-08 14:39 6.00 2.421 * 0.02 19.7 0 2.9 Lecheria I 26-Nov-08 14:45 6.00 1.910 * 0.20 20.7 0 7.4 Lecheria O 26-Nov-08 14:53 5.94 3.178 * 0.02 17.7 0 17.2 Lecheria W 26-Nov-08 14:55 5.93 2.914 0.01 0.02 20.3 0 3.7 LaPA I-B1 26-Nov-08 15:57 6.15 3.195 * 0.02 15.0 0 3.9 LaPA I-A 26-Nov-08 16:10 6.14 1.400 * 0.02 22.3 0 13.2 LaPA I-B2 26-Nov-08 16:20 6.20 1.593 0.11 0.02 15.7 0 4.7 LaPA O 26-Nov-08 16:27 6.22 2.702 * 0.02 15.3 0 4.0 Empacadora S-A 28-Nov-08 8:10 7.04 3.195 0.07 0.08 20.0 0 1.3 Empacadora S-B 28-Nov-08 8:15 7.04 1.558 0.13 0.06 8.7 0 2.0 Empacadora S-B 28-Nov-08 8:15 7.05 3.195 0.29 0.08 19.3 0 1.8 Empacadora S-C 28-Nov-08 8:20 7.25 1.928 0.26 0.06 14.0 35 1.7 Empacadora R 28-Nov-08 8:30 6.87 3.195 0.01 0.04 2.0 0 1.8 Papel O 28-Nov-08 9:37 6.14 3.160 0.49 0.08 13.0 0 0.3 Papel O 28-Nov-08 9:37 6.10 2.597 0.52 0.02 18.3 0 0.3 Papel I 28-Nov-08 9:42 6.10 1.048 0.46 0.02 12.7 0 0.4 BLANK * 28-Nov-08 * 5.00 1.276 * 0.09 6.7 0 0.5 Papel O 28-Nov-08 9:55 5.86 2.121 0.37 0.03 18.0 0 0.7 Papel R 28-Nov-08 9:51 6.10 44.630 0.27 0.02 20.5 0 0.5 Papel I-A1 28-Nov-08 10:00 4.78 17.945 4.38 3.72 51.5 0 37.0 LaPA S-E 30-Nov-08 10:26 4.93 2.782 0.09 1.74 206.5 640 84.0 LaPA S-G 30-Nov-08 10:33 6.95 0.977 * 0.96 217.0 7 29.0

Continued 147 Table A1 continued

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) LaPA S-A 30-Nov-08 10:55 6.02 1.136 0.23 0.52 272.5 192 34.0 LaPA S-B 30-Nov-08 10:18 * * * * * * * LaPA S-D 30-Nov-08 10:23 * * * * * * * LaPA S-F 30-Nov-08 10:23 * * * * * * * LaPA I-A 28-Jan-09 11:02 6.88 0.000 0.46 0.17 73.5 7 19.8 LaPA I-B1 28-Jan-09 11:20 7.04 0.000 0.61 0.00 0.0 0 11.1 LaPA I-B2 28-Jan-09 11:28 6.70 0.000 0.44 0.00 0.0 5 17.7 LaPA O 28-Jan-09 11:38 6.88 0.988 0.08 0.00 0.8 2 9.8 LaPA R 28-Jan-09 11:45 6.89 0.132 0.03 0.00 0.0 0 9.7 Sanitario I-A2 28-Jan-09 12:26 6.42 4.934 0.79 0.00 0.0 0 4.0 Sanitario O 28-Jan-09 12:31 6.46 5.909 0.99 0.00 0.0 0 1.5 Lecheria I-B 27-Jan-09 13:20 6.89 0.000 0.14 0.00 0.0 0 4.1 Canal O 27-Jan-09 11:41 7.29 82.937 0.35 3.24 0.0 56 31.0 Canal I 27-Jan-09 11:35 7.24 85.578 0.37 3.54 0.0 63 24.0 Lecheria I-B2 27-Jan-09 * 6.75 15.775 0.11 2.82 32.3 340 224.0 Canal O 27-Jan-09 11:33 7.21 120.270 0.51 4.18 15.8 72 35.0 Canal I 27-Jan-09 11:10 7.12 79.336 0.31 3.66 0.0 61 29.0 Canal I 27-Jan-09 11:26 7.20 86.899 0.23 4.90 24.8 40 28.0 Lecheria I-B1 27-Jan-09 12:25 6.50 8.512 0.18 4.28 60.0 480 459.0 Canal O 27-Jan-09 11:24 7.24 74.774 0.29 4.40 18.0 69 30.0 Canal O 27-Jan-09 11:16 7.30 94.581 0.34 4.73 19.8 90 28.0 Canal I 27-Jan-09 11:19 7.33 92.720 0.48 4.45 10.5 54 22.0 Biodigestor I 27-Jan-09 10:47 7.40 4.791 0.13 4.45 14.3 200 162.0 Biodigestor O 27-Jan-09 10:48 6.86 103.524 2.18 4.91 28.5 380 71.0 Canal O 27-Jan-09 10:56 6.96 102.024 1.31 2.49 10.8 80 35.0 Canal O 27-Jan-09 11:05 7.14 95.481 0.32 2.77 4.3 64 25.0 Canal I 27-Jan-09 11:01 6.99 101.183 0.00 3.89 36.8 40 58.0 Lecheria I-B4 27-Jan-09 12:46 6.73 10.966 0.00 0.03 6.5 1240 38.0 Lecheria I-B3 27-Jan-09 12:37 6.95 14.057 0.06 1.74 8.2 80 168.0 Lecheria I-A 27-Jan-09 12:54 7.36 63.911 0.34 3.08 1.8 46 28.0 Lecheria I 27-Jan-09 13:03 6.49 4.064 1.29 0.05 3.0 17 28.0 Lecheria O 27-Jan-09 13:17 6.26 0.000 2.07 0.00 6.5 49 24.0 Lecheria O 27-Jan-09 12:59 6.33 2.788 0.96 0.01 4.5 16 6.0 Lecheria O 27-Jan-09 13:46 6.11 0.000 0.52 0.00 9.5 0 6.9 Lecheria O 27-Jan-09 13:34 5.81 0.000 0.16 0.01 24.3 1 2.0 Lecheria I 27-Jan-09 13:38 6.01 0.000 0.59 0.00 11.8 0 13.5 Lecheria W 27-Jan-09 13:52 6.07 0.000 0.51 0.00 14.3 0 7.1 Sanitario I-A1 27-Jan-09 12:36 6.24 6.345 0.17 0.00 0.0 1 107.0 Lecheria I-A 27-Jan-09 13:28 6.19 0.000 1.43 0.00 0.0 12 15.8 Dos Novillos S-A 28-Jan-09 10:15 7.11 0.000 0.09 0.00 5.8 1 2.8 Dos Novillos S-B 28-Jan-09 12:20 7.31 0.000 0.11 0.00 2.0 0 2.4 Dos Novillos S-C 29-Jan-09 9:50 7.37 0.000 0.16 0.04 4.8 5 1.6 Dos Novillos S-E 28-Jan-09 15:18 7.21 0.000 0.14 0.00 24.5 0 2.9 BLANK * 1-Feb-09 * 7.55 0.000 0.04 0.00 8.5 0 0.9 Papel I-A2 6-Feb-09 7:54 6.35 4.129 0.59 0.00 0.0 0 0.3 Papel I-B 6-Feb-09 8:02 6.62 0.000 0.99 0.00 25.3 0 1.1

Continued 148 Table A1 continued

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) Papel I 6-Feb-09 8:21 6.25 0.000 0.12 0.00 0.0 0 1.1 Papel I 6-Feb-09 8:21 6.24 0.000 0.08 0.00 0.0 0 2.0 Papel O 6-Feb-09 8:32 6.33 0.000 0.02 0.00 15.8 0 1.1 Papel R 6-Feb-09 8:35 6.44 0.000 0.01 0.00 41.0 0 0.8 Empacadora S-A 6-Feb-09 9:02 7.38 0.000 3.93 0.44 9.5 33 4.5 Empacadora S-B 6-Feb-09 9:07 7.43 0.000 4.48 0.40 5.3 44 4.7 Empacadora S-C 6-Feb-09 9:12 7.38 0.000 4.80 0.41 7.8 39 3.9 Empacadora S-D 6-Feb-09 9:16 7.42 0.000 4.51 0.42 3.8 83 4.5 Empacadora S-E 6-Feb-09 9:20 7.33 2.397 4.47 0.42 0.0 60 4.9 Empacadora S-F 6-Feb-09 9:25 7.36 1.215 4.44 0.45 15.8 57 3.5 Empacadora R 6-Feb-09 9:34 7.33 0.000 4.71 0.40 6.5 60 3.6 LaPA S-C 6-Feb-09 9:55 4.29 2.930 3.61 3.26 112.5 1590 73.0 LaPA S-D 6-Feb-09 10:05 5.38 8.158 1.29 4.00 72.5 124 59.0 LaPA S-E 6-Feb-09 10:10 5.40 1.065 1.10 4.11 126.5 276 50.0 LaPA S-F 6-Feb-09 10:14 5.62 6.909 0.00 4.26 117.3 330 37.0 LaPA S-G 6-Feb-09 10:23 6.34 4.345 0.76 3.63 91.8 268 21.0 Lecheria I-B1 13-Feb-09 7:30 6.85 30.095 0.44 8.80 119.8 1600 318.0 Lecheria O 13-Feb-09 7:46 6.97 23.230 0.04 1.70 1.8 85 39.0 Lecheria I 13-Feb-09 7:51 6.75 12.248 0.31 0.51 1.0 55 28.0 Lecheria O 13-Feb-09 7:56 6.56 4.719 0.56 0.20 1.7 49 19.0 Lecheria I-A 13-Feb-09 8:01 6.53 3.856 0.58 0.22 0.0 42 19.0 Lecheria O 13-Feb-09 8:15 6.27 0.000 0.07 0.05 2.0 38 8.6 Lecheria I-B 13-Feb-09 8:09 6.62 0.000 0.00 0.01 5.7 9 5.2 Lecheria I-B 13-Feb-09 8:09 6.64 0.000 0.00 0.01 0.0 10 3.8 Lecheria I 13-Feb-09 8:17 6.39 0.000 0.03 0.02 11.5 12 12.4 Lecheria O 13-Feb-09 8:22 6.25 0.000 0.00 0.01 0.0 10 5.4 Lecheria W 13-Feb-09 8:40 6.36 0.000 0.05 0.21 1.3 17 7.1 Biodigestor I 13-Feb-09 8:49 7.44 96.531 1.42 32.98 114.8 3000 213.0 Biodigestor O 13-Feb-09 8:51 6.95 95.097 0.32 3.03 23.5 100 22.0 Canal O 13-Feb-09 9:01 7.46 91.113 0.38 2.50 5.0 70 13.1 Canal I 13-Feb-09 9:31 7.49 88.510 0.47 2.56 13.3 102 13.8 Canal O 13-Feb-09 9:09 7.25 85.908 0.24 2.96 10.8 89 15.2 Canal I 13-Feb-09 9:06 7.27 83.570 0.26 3.01 11.8 127 13.7 Canal O 13-Feb-09 9:39 7.13 79.640 0.75 2.99 57.0 50 26.0 Canal I 13-Feb-09 9:34 7.15 80.277 0.37 3.10 78.0 110 26.0 Canal I 13-Feb-09 9:46 7.27 78.524 0.70 3.05 63.5 100 20.0 Canal O 13-Feb-09 9:49 7.26 81.711 0.82 3.38 68.8 250 29.0 Canal I 13-Feb-09 9:53 7.17 84.155 1.24 3.06 65.0 100 27.0 Canal O 13-Feb-09 9:59 7.16 75.656 1.19 2.90 82.0 250 29.0 Canal O 13-Feb-09 10:03 7.57 79.162 0.51 2.85 12.0 138 17.9 Lecheria I-A 13-Feb-09 10:11 7.53 78.365 0.51 2.91 25.0 100 23.0 Lecheria I-B3 13-Feb-09 10:23 7.05 12.580 0.11 1.59 87.5 250 123.0 Lecheria I-B4 13-Feb-09 10:31 7.00 16.577 0.16 2.92 45.8 350 137.0 BLANK * 13-Feb-09 * 7.50 0.000 0.00 0.16 5.0 3 0.9 Dos Novillos S-A 16-Feb-09 8:30 7.20 0.000 0.02 0.04 0.0 0 3.4 Dos Novillos S-B 16-Feb-09 11:15 7.46 0.000 0.02 0.03 0.0 0 0.5

Continued 149 Table A1 continued

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) Dos Novillos S-D 15-Feb-09 9:15 7.39 0.000 0.12 0.11 0.0 7 1.18 Dos Novillos S-E 16-Feb-09 14:00 7.45 0.000 0.09 0.02 0.0 4 3.3 Dos Novillos S-F 15-Feb-09 12:35 7.35 0.000 0.13 0.03 0.0 10 1.40 Sanitario O 18-Feb-09 7:30 5.93 0.000 4.70 0.11 15.3 14 0.982 Sanitario I-A2 18-Feb-09 7:46 5.79 0.000 2.08 0.10 12.5 11 0.765 Sanitario W 18-Feb-09 7:55 6.19 0.000 0.00 0.05 6.5 83 5.85 Papel I-A1 18-Feb-09 8:44 5.39 28.873 5.52 7.59 127.5 1800 124 Papel O 18-Feb-09 8:55 6.02 0.000 0.28 0.10 3.8 4 0.769 Papel I-A2 18-Feb-09 9:40 5.50 14.386 2.11 2.52 128.0 900 81.1 Papel I-B 18-Feb-09 9:45 6.37 0.000 1.14 0.04 1.3 12 1.37 Papel I 18-Feb-09 9:50 6.19 0.000 0.31 0.03 1.8 11 0.348 Papel O 18-Feb-09 9:54 6.22 0.000 0.21 0.12 0.8 9 0.231 Papel R 18-Feb-09 9:59 6.29 0.000 0.21 0.02 19.3 10 0.203 LaPA S-D 18-Feb-09 10:40 4.46 0.000 4.88 3.27 124.8 1840 64.1 LaPA S-E 18-Feb-09 10:44 4.46 0.000 5.00 2.82 127.3 1660 71.9 LaPA S-F 18-Feb-09 10:46 4.57 0.000 4.37 2.94 128.3 1360 56.0 LaPA I-A 18-Feb-09 10:57 6.08 0.000 0.02 0.48 42.8 130 19.4 LaPA I-B2 18-Feb-09 11:02 6.44 0.000 0.14 0.08 15.5 5 15.8 LaPA I-B1 18-Feb-09 11:11 6.48 0.000 0.16 0.08 3.3 14 15.6 LaPA O 18-Feb-09 11:24 6.47 0.000 0.00 0.04 13.8 15 9.23 LaPA R 18-Feb-09 11:30 6.56 0.000 0.12 0.04 0.0 7 9.45 LaPA S-C 3-Mar-09 15:37 4.01 1.437 3.65 2.71 129.0 * 60.1 LaPA S-D 3-Mar-09 15:47 4.65 7.363 3.42 2.85 124.0 * 73.4 LaPA S-E 3-Mar-09 15:52 4.66 8.854 3.33 2.06 121.3 * 76.9 LaPA S-F 3-Mar-09 15:55 4.94 10.725 3.49 2.24 125.3 * 61.3 LaPA S-G 3-Mar-09 16:02 6.06 10.476 1.75 2.42 124.0 * 44.6 LaPA I-A 3-Mar-09 16:20 6.41 0.000 0.21 0.87 45.0 * 13.1 LaPA I-B1 3-Mar-09 16:13 6.79 0.000 0.12 0.01 9.3 * 1.38 LaPA I-B2 3-Mar-09 16:24 6.53 0.000 0.19 0.57 14.0 * 6.98 LaPA O 3-Mar-09 16:38 6.75 0.000 0.00 0.10 11.8 * 6.52 LaPA R 3-Mar-09 16:41 6.73 0.000 0.00 0.04 13.5 * 6.46 Dos Novillos S-A 2-Mar-09 9:30 7.33 0.000 0.07 0.10 15.5 * 0.154 Dos Novillos S-B 2-Mar-09 13:15 7.52 0.000 0.01 0.03 6.8 * 0.272 Dos Novillos S-C 1-Mar-09 16:40 7.38 0.000 0.04 0.02 13.3 * 0.256 Dos Novillos S-D 3-Mar-09 9:00 7.27 0.000 0.05 0.03 15.0 * 0.594 Dos Novillos S-E 2-Mar-09 15:50 7.34 0.000 0.05 0.05 10.8 * 0.342 Dos Novillos S-F 3-Mar-09 10:45 7.36 0.000 0.14 0.04 10.8 * 0.392 Lecheria W 4-Mar-09 8:00 6.55 0.000 0.00 0.04 7.8 * 4.29 Lecheria O 4-Mar-09 8:04 6.30 0.000 0.00 0.03 21.3 * 4.35 Lecheria I 4-Mar-09 8:12 6.21 0.000 0.00 0.04 11.8 * 5.43 Lecheria O 4-Mar-09 8:17 6.30 0.000 0.00 0.04 10.5 * 6.33 Lecheria I-B 4-Mar-09 8:24 6.57 0.000 0.00 0.06 7.3 * 5.84 Lecheria I-A 4-Mar-09 8:30 6.28 0.403 0.00 0.20 8.0 * 12.8 Lecheria O 4-Mar-09 8:38 6.15 0.495 0.00 0.25 5.3 * 13.7 Lecheria I 4-Mar-09 8:44 6.45 21.295 0.00 1.70 15.8 * 27.0 Lecheria O 4-Mar-09 8:48 6.51 19.908 0.00 1.43 26.5 * 26.6

Continued 150 Table A1 continued

NH4 NO3 PO4 BOD COD Turbidity Site Location Date Time pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (TAU) Canal O 4-Mar-09 9:07 6.88 84.605 0.20 3.36 15.0 * 14.6 Canal I 4-Mar-09 9:09 7.44 93.867 0.26 3.45 115.8 * 17.8 Canal I 4-Mar-09 9:14 7.75 87.744 0.23 3.71 15.5 * 13.8 Canal O 4-Mar-09 9:17 7.67 87.483 0.11 3.43 40.8 * 15.6 Canal O 4-Mar-09 9:22 7.42 95.436 0.25 3.55 21.3 * 17.8 Canal I 4-Mar-09 9:59 7.10 84.029 0.54 3.08 51.8 * 12.0 Canal O 4-Mar-09 10:03 7.11 101.977 0.50 3.40 11.3 * 12.8 Biodigestor O 4-Mar-09 10:06 6.81 83.453 0.47 3.78 56.8 * 39.1 Canal I 4-Mar-09 10:11 7.40 98.942 0.40 3.78 16.8 * 14.5 Canal O 4-Mar-09 10:14 7.43 98.524 0.44 2.90 5.8 * 15.1 Canal I 4-Mar-09 10:16 6.94 100.251 0.27 2.84 0.0 * 24.5 Canal O 4-Mar-09 10:21 6.93 97.948 0.27 2.94 13.3 * 25.9 Biodigestor I 4-Mar-09 10:26 7.24 25.377 0.00 8.26 64.0 * 219 Lecheria I-B3 4-Mar-09 10:39 7.23 27.666 1.38 4.61 30.0 * 64.0 Lecheria I-B2 4-Mar-09 10:45 6.49 29.197 2.11 4.89 52.5 * 88.3 Lecheria I-B1 4-Mar-09 10:48 6.76 1.868 0.20 0.34 5.0 * 9.34 Lecheria I-B1 4-Mar-09 10:48 6.82 1.201 0.18 0.33 13.8 * 8.54 Empacadora S-A 4-Mar-09 11:01 7.32 0.468 5.28 0.53 13.5 * 4.68 Empacadora S-B 4-Mar-09 11:17 7.15 2.261 5.35 0.48 15.8 * 5.23 Empacadora S-C 4-Mar-09 11:20 7.36 3.438 4.40 0.53 9.5 * 2.11 Empacadora S-D 4-Mar-09 11:29 7.48 0.000 3.89 0.53 6.5 * 2.79 Empacadora S-E 4-Mar-09 11:26 7.51 0.000 4.16 0.58 5.5 * 2.30 Empacadora S-F 4-Mar-09 11:23 7.55 0.000 4.13 0.52 4.0 * 1.82 Empacadora R 4-Mar-09 11:39 7.63 3.111 3.68 0.53 8.5 * 2.16 Sanitario I-A2 4-Mar-09 13:24 6.42 0.000 0.00 0.02 3.3 * 1.93 Sanitario O 4-Mar-09 13:30 6.79 0.000 0.00 0.01 11.8 * 1.61 Papel I-A1 4-Mar-09 13:58 5.68 0.000 0.81 2.72 62.8 * 8.26 Papel I-A2 4-Mar-09 14:14 6.27 1.986 0.48 0.18 17.8 * 0.616 Papel I-B 4-Mar-09 14:17 6.46 0.000 0.90 0.88 6.3 * 0.202 Papel O 4-Mar-09 14:22 6.30 0.037 0.00 1.97 14.5 * 2.59 Papel I 4-Mar-09 14:23 6.29 0.000 0.00 2.27 19.5 * 2.54 Papel I 4-Mar-09 14:23 6.30 0.000 0.00 2.27 11.5 * 2.79 Papel O 4-Mar-09 14:35 6.36 0.000 0.06 0.10 5.5 * 1.73 Papel R 4-Mar-09 14:37 6.50 0.000 0.04 0.09 12.8 * 1.51 BLANK * 4-Mar-09 * 6.27 0.000 0.02 0.03 9.3 * 0.223

151

Appendix B: Raw In-Field Data from Tropical Treatment Wetlands in Costa Rica

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP Lecheria I-B3 15-Aug-08 * 29.00 * 3.70 7.10 * Lecheria O 15-Aug-08 * 29.00 * 0.30 6.71 * Lecheria I 15-Aug-08 * 29.00 * 0.22 6.68 * Lecheria O 15-Aug-08 * 28.00 * 0.86 6.32 * Lecheria I-A 15-Aug-08 * 29.00 * 1.26 6.59 * Lecheria O 15-Aug-08 * 30.00 * 0.70 6.99 * Lecheria I 15-Aug-08 * 30.00 * 1.29 5.92 * Lecheria O 15-Aug-08 * 30.00 * 0.70 6.32 * Sanitario I-A2 15-Aug-08 * 28.00 * 4.34 6.69 * Sanitario O 15-Aug-08 * 28.00 * 4.07 6.74 * LaPA I-A 15-Aug-08 * 28.00 * 1.71 6.82 * LaPA O 15-Aug-08 * 25.90 * 4.26 6.74 * LaPA R 15-Aug-08 * 25.90 * 5.83 6.93 * Papel I-B 15-Aug-08 * 27.50 * 5.85 6.70 * Papel O 15-Aug-08 * 27.00 * 0.73 6.24 * Empacadora S-B 18-Aug-08 * 27.60 * 6.50 7.50 * Empacadora S-C 18-Aug-08 * 27.70 * 5.84 7.52 * Empacadora S-D 18-Aug-08 * 27.80 * 5.93 7.46 * Empacadora S-E 18-Aug-08 * 28.20 * 5.94 7.47 * Empacadora S-F 18-Aug-08 * 28.20 * 5.80 7.50 * Empacadora R 18-Aug-08 * 28.30 * 5.74 * * Biodigestor I 5-Sep-08 * 26.30 * 5.46 * * Biodigestor O 5-Sep-08 * 26.30 * 1.16 * * Biodigestor O 5-Sep-08 * 26.40 * 1.32 * * Canal O 5-Sep-08 * 26.90 * 0.51 * * Canal I 5-Sep-08 * 26.90 * 0.17 * * Canal O 5-Sep-08 * 26.90 * 0.13 * * Canal I 5-Sep-08 * 26.40 * 0.73 * * Canal O 5-Sep-08 * 26.80 * 0.25 * * Canal I 5-Sep-08 * 26.80 * 1.29 * * Canal O 5-Sep-08 * 26.20 * 0.28 * * Canal I 5-Sep-08 * 26.40 * 0.87 * * Canal O 5-Sep-08 * 27.20 * 0.27 * * Canal I 5-Sep-08 * 26.50 * 1.20 * * Canal O 5-Sep-08 * 26.40 * 0.42 * *

Table B1. In-field data, including temperature, conductivity, dissolved oxygen (DO), pH, and oxidation-reduction potential (ORP) measured from tropical treatment wetlands. 152 Table B1 continued

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP Sanitario O 26-Nov-08 9:30 27.83 0.043 4.60 5.56 * Biodigestor I 26-Nov-08 10:15 27.13 0.462 1.31 6.86 * Biodigestor O 26-Nov-08 10:20 26.50 2.091 1.09 6.80 * Canal O 26-Nov-08 10:25 27.63 2.048 0.15 6.86 * Canal I 26-Nov-08 10:30 28.16 2.051 0.29 6.93 * Canal O 26-Nov-08 10:32 26.93 1.929 0.23 7.31 * Canal I 26-Nov-08 10:36 27.76 1.940 0.64 7.28 * Canal O 26-Nov-08 10:40 26.27 1.822 0.69 7.58 * Canal I 26-Nov-08 10:42 27.14 1.798 1.37 7.62 * Canal O 26-Nov-08 10:45 27.04 1.708 1.38 7.60 * Canal I 26-Nov-08 10:51 29.62 1.563 1.48 7.59 * Canal O 26-Nov-08 10:55 27.24 1.498 0.59 7.55 * Canal I 26-Nov-08 10:57 28.26 1.489 2.14 7.63 * Canal O 26-Nov-08 11:00 28.69 1.447 1.62 7.62 * Lecheria I-B2 26-Nov-08 13:40 * * * * * Lecheria I-B3 26-Nov-08 13:43 27.72 0.472 1.08 6.70 * Lecheria I-B1 26-Nov-08 13:45 * * * * * Lecheria I-B4 26-Nov-08 13:48 28.83 0.474 0.23 6.49 * Lecheria I-A 26-Nov-08 13:52 25.94 0.169 1.65 6.24 * Lecheria O 26-Nov-08 13:57 25.88 0.185 0.18 6.15 * Lecheria I 26-Nov-08 14:00 28.97 0.448 2.33 6.02 * Lecheria O 26-Nov-08 14:03 25.50 0.144 0.17 6.06 * Lecheria I-A 26-Nov-08 14:30 26.22 0.047 1.91 6.01 * Lecheria I-B 26-Nov-08 14:35 26.20 0.052 5.45 6.28 * Lecheria O 26-Nov-08 14:39 25.23 0.071 1.59 5.75 * Lecheria I 26-Nov-08 14:45 26.40 0.072 0.86 5.83 * Lecheria O 26-Nov-08 14:53 26.77 0.065 0.33 5.67 * Lecheria W 26-Nov-08 14:55 * * * * * LaPA I-B1 26-Nov-08 15:57 25.89 0.051 6.61 6.26 * LaPA I-A 26-Nov-08 16:10 28.00 0.065 2.53 6.13 * LaPA I-B2 26-Nov-08 16:20 26.03 0.051 5.84 6.30 * LaPA O 26-Nov-08 16:27 26.42 0.055 4.41 6.07 * Empacadora S-A 28-Nov-08 8:10 25.79 0.135 6.40 7.59 * Empacadora S-B 28-Nov-08 8:15 25.90 0.132 5.96 7.48 * Empacadora S-B 28-Nov-08 8:15 * * * * * Empacadora S-C 28-Nov-08 8:20 25.90 0.132 6.77 7.44 * Empacadora R 28-Nov-08 8:30 26.00 0.128 6.84 6.91 * Papel O 28-Nov-08 9:37 25.96 0.101 0.51 5.80 * Papel O 28-Nov-08 9:37 * * * * * Papel I 28-Nov-08 9:42 25.95 0.101 0.78 5.92 * BLANK * 28-Nov-08 * * * * * * Papel O 28-Nov-08 9:55 25.91 0.100 1.24 5.99 * Papel R 28-Nov-08 9:51 25.92 0.100 2.02 5.97 * Papel I-A1 28-Nov-08 10:00 25.69 6.618 5.53 4.13 * LaPA S-E 30-Nov-08 10:26 26.68 0.658 1.49 5.00 * LaPA S-G 30-Nov-08 10:33 26.73 0.621 0.09 6.16 *

Continued 153 Table B1 continued

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP LaPA S-A 30-Nov-08 10:55 27.42 0.195 5.29 6.93 * LaPA S-B 30-Nov-08 10:18 28.16 0.286 2.42 5.14 * LaPA S-D 30-Nov-08 10:23 26.77 0.695 1.92 4.86 * LaPA S-F 30-Nov-08 10:23 26.85 0.649 0.12 5.35 * LaPA I-A 28-Jan-09 11:02 24.02 0.061 4.40 6.67 80 LaPA I-B1 28-Jan-09 11:20 24.56 0.047 5.20 6.47 114 LaPA I-B2 28-Jan-09 11:28 24.15 0.046 5.20 6.18 144 LaPA O 28-Jan-09 11:38 23.77 0.044 6.23 6.38 140 LaPA R 28-Jan-09 11:45 23.57 0.045 6.78 6.32 121 Sanitario I-A2 28-Jan-09 12:26 25.18 0.106 3.59 6.42 47 Sanitario O 28-Jan-09 12:31 24.84 0.104 2.92 6.23 125 Lecheria I-B 27-Jan-09 13:20 23.96 0.045 7.05 6.27 97 Canal O 27-Jan-09 11:41 23.80 1.040 0.77 7.30 -59 Canal I 27-Jan-09 11:35 23.03 0.937 1.47 7.27 -132 Lecheria I-B2 27-Jan-09 * * * * * * Canal O 27-Jan-09 11:33 22.77 0.996 0.11 7.19 -188 Canal I 27-Jan-09 11:10 22.85 1.441 0.30 7.07 -130 Canal I 27-Jan-09 11:26 23.46 1.129 0.21 7.22 -121 Lecheria I-B1 27-Jan-09 12:25 23.46 0.792 1.87 6.53 -97 Canal O 27-Jan-09 11:24 23.11 1.185 0.08 7.18 -108 Canal O 27-Jan-09 11:16 22.62 1.408 0.09 7.25 -152 Canal I 27-Jan-09 11:19 22.77 1.396 1.19 7.26 -133 Biodigestor I 27-Jan-09 10:47 24.24 0.305 5.65 7.65 172 Biodigestor O 27-Jan-09 10:48 23.29 1.678 2.60 6.85 -161 Canal O 27-Jan-09 10:56 23.41 1.650 0.25 6.91 -200 Canal O 27-Jan-09 11:05 22.85 1.444 0.22 7.08 -110 Canal I 27-Jan-09 11:01 23.36 1.611 0.38 6.93 -180 Lecheria I-B4 27-Jan-09 12:46 24.93 0.354 0.32 6.65 -125 Lecheria I-B3 27-Jan-09 12:37 25.80 0.399 0.35 6.83 -101 Lecheria I-A 27-Jan-09 12:54 24.24 0.938 1.26 6.97 -177 Lecheria I 27-Jan-09 13:03 23.56 0.114 1.00 6.14 41 Lecheria O 27-Jan-09 13:17 23.42 0.092 0.18 5.99 108 Lecheria O 27-Jan-09 12:59 23.67 0.108 0.62 6.28 42 Lecheria O 27-Jan-09 13:46 23.73 0.051 0.68 5.62 193 Lecheria O 27-Jan-09 13:34 24.26 0.029 0.97 5.53 154 Lecheria I 27-Jan-09 13:38 23.72 0.051 0.53 5.66 158 Lecheria W 27-Jan-09 13:52 23.78 0.051 6.13 6.07 83 Sanitario I-A1 27-Jan-09 12:36 25.46 0.173 4.60 6.59 5 Lecheria I-A 27-Jan-09 13:28 23.52 0.081 2.60 6.15 119 Dos Novillos S-A 28-Jan-09 10:15 19.20 33.300 10.26 * * Dos Novillos S-B 28-Jan-09 12:20 20.30 30.200 10.01 * * Dos Novillos S-C 29-Jan-09 9:50 21.40 42.200 9.70 * * Dos Novillos S-E 28-Jan-09 15:18 21.95 0.038 8.87 6.85 143 BLANK * 1-Feb-09 * * * * * * Papel I-A2 6-Feb-09 7:54 25.18 0.081 3.90 6.36 97 Papel I-B 6-Feb-09 8:02 25.25 0.088 6.21 6.59 102

Continued 154 Table B1 continued

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP Papel I 6-Feb-09 8:21 24.85 0.081 0.68 6.01 67 Papel I 6-Feb-09 8:21 * * * * * Papel O 6-Feb-09 8:32 24.62 0.046 1.33 6.20 97 Papel R 6-Feb-09 8:35 24.68 0.084 3.71 6.29 71 Empacadora S-A 6-Feb-09 9:02 25.51 0.121 6.83 7.45 49 Empacadora S-B 6-Feb-09 9:07 25.49 0.123 6.88 7.56 43 Empacadora S-C 6-Feb-09 9:12 25.49 0.122 7.90 7.52 46 Empacadora S-D 6-Feb-09 9:16 25.43 0.122 6.82 7.42 49 Empacadora S-E 6-Feb-09 9:20 25.47 0.123 6.81 7.47 57 Empacadora S-F 6-Feb-09 9:25 25.48 0.123 6.97 7.50 48 Empacadora R 6-Feb-09 9:34 25.38 0.123 6.92 7.53 50 LaPA S-C 6-Feb-09 9:55 26.10 0.514 0.54 4.46 30 LaPA S-D 6-Feb-09 10:05 25.57 0.599 0.09 5.48 -37 LaPA S-E 6-Feb-09 10:10 25.57 0.599 0.13 5.44 -47 LaPA S-F 6-Feb-09 10:14 25.54 0.608 0.08 5.66 -104 LaPA S-G 6-Feb-09 10:23 25.23 0.656 0.33 6.39 -149 Lecheria I-B1 13-Feb-09 7:30 23.04 1.231 1.91 6.86 -163 Lecheria O 13-Feb-09 7:46 23.35 0.409 0.30 6.88 -140 Lecheria I 13-Feb-09 7:51 23.45 0.259 0.29 6.66 -49 Lecheria O 13-Feb-09 7:56 23.41 0.165 0.10 6.32 23 Lecheria I-A 13-Feb-09 8:01 23.64 0.130 1.55 6.23 27 Lecheria O 13-Feb-09 8:15 24.00 0.067 0.74 6.25 78 Lecheria I-B 13-Feb-09 8:09 23.35 0.051 6.68 6.50 54 Lecheria I-B 13-Feb-09 8:09 * * * * * Lecheria I 13-Feb-09 8:17 23.82 0.066 0.60 6.24 87 Lecheria O 13-Feb-09 8:22 23.87 0.061 0.31 6.07 82 Lecheria W 13-Feb-09 8:40 24.02 0.061 5.93 6.61 47 Biodigestor I 13-Feb-09 8:49 23.26 3.918 0.10 7.53 -240 Biodigestor O 13-Feb-09 8:51 23.56 1.850 1.93 6.90 -167 Canal O 13-Feb-09 9:01 23.26 1.450 0.45 7.22 -148 Canal I 13-Feb-09 9:31 23.52 1.636 1.37 7.25 -65 Canal O 13-Feb-09 9:09 23.05 1.411 0.05 7.15 -204 Canal I 13-Feb-09 9:06 23.22 1.252 0.40 7.26 -161 Canal O 13-Feb-09 9:39 23.18 1.162 0.08 7.06 -208 Canal I 13-Feb-09 9:34 23.39 1.048 1.15 7.14 -85 Canal I 13-Feb-09 9:46 23.66 1.108 0.90 7.18 -188 Canal O 13-Feb-09 9:49 22.85 1.127 0.20 7.18 -202 Canal I 13-Feb-09 9:53 23.65 1.158 0.64 7.23 -185 Canal O 13-Feb-09 9:59 23.50 1.160 0.27 7.11 -209 Canal O 13-Feb-09 10:03 23.44 1.174 0.36 7.43 -173 Lecheria I-A 13-Feb-09 10:11 25.60 1.130 2.77 7.51 -117 Lecheria I-B3 13-Feb-09 10:23 28.50 0.436 3.32 7.10 -41 Lecheria I-B4 13-Feb-09 10:31 26.85 0.547 1.11 6.79 -161 BLANK * 13-Feb-09 * * * * * * Dos Novillos S-A 16-Feb-09 8:30 19.78 0.042 8.98 7.07 * Dos Novillos S-B 16-Feb-09 11:15 21.66 0.042 9.13 7.64 *

Continued 155 Table B1 continued

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP Dos Novillos S-D 15-Feb-09 9:15 21.94 0.041 8.89 6.38 * Dos Novillos S-E 16-Feb-09 14:00 24.07 0.047 9.05 7.34 * Dos Novillos S-F 15-Feb-09 12:35 23.41 0.054 8.24 6.79 * Sanitario O 18-Feb-09 7:30 24.42 0.077 2.79 6.54 147 Sanitario I-A2 18-Feb-09 7:46 24.44 0.059 2.81 6.06 171 Sanitario W 18-Feb-09 7:55 23.00 0.079 2.74 6.30 141 Papel I-A1 18-Feb-09 8:44 23.95 1.935 2.85 6.41 64 Papel O 18-Feb-09 8:55 24.94 0.081 0.51 5.94 27 Papel I-A2 18-Feb-09 9:40 24.66 1.003 3.45 6.28 85 Papel I-B 18-Feb-09 9:45 25.29 0.089 5.49 6.33 80 Papel I 18-Feb-09 9:50 24.99 0.081 1.18 6.08 56 Papel O 18-Feb-09 9:54 24.87 0.082 1.36 6.19 72 Papel R 18-Feb-09 9:59 24.86 0.082 3.66 6.28 60 LaPA S-D 18-Feb-09 10:40 25.86 0.639 0.32 4.52 -35 LaPA S-E 18-Feb-09 10:44 25.61 0.662 0.12 4.57 -57 LaPA S-F 18-Feb-09 10:46 25.58 0.678 0.11 4.68 -82 LaPA I-A 18-Feb-09 10:57 24.53 0.137 3.09 6.08 -26 LaPA I-B2 18-Feb-09 11:02 24.49 0.061 3.48 6.37 12 LaPA I-B1 18-Feb-09 11:11 24.95 0.053 3.67 6.40 25 LaPA O 18-Feb-09 11:24 24.04 0.054 5.77 6.35 59 LaPA R 18-Feb-09 11:30 24.00 0.057 5.54 6.50 60 LaPA S-C 3-Mar-09 15:37 27.91 0.588 0.97 4.75 -83 LaPA S-D 3-Mar-09 15:47 28.05 0.620 0.30 4.68 -82 LaPA S-E 3-Mar-09 15:52 28.26 0.742 0.06 4.84 -92 LaPA S-F 3-Mar-09 15:55 28.13 0.750 0.17 5.12 -124 LaPA S-G 3-Mar-09 16:02 28.39 0.780 0.31 6.08 -182 LaPA I-A 3-Mar-09 16:20 27.16 0.265 2.42 6.32 -75 LaPA I-B1 3-Mar-09 16:13 26.86 0.068 1.30 6.66 -20 LaPA I-B2 3-Mar-09 16:24 26.19 0.140 2.50 6.44 -123 LaPA O 3-Mar-09 16:38 25.75 0.065 4.42 6.49 15 LaPA R 3-Mar-09 16:41 25.92 0.065 5.29 6.49 29 Dos Novillos S-A 2-Mar-09 9:30 19.80 61.200 9.20 * * Dos Novillos S-B 2-Mar-09 13:15 24.50 58.000 9.23 * * Dos Novillos S-C 1-Mar-09 16:40 25.20 57.200 8.46 * * Dos Novillos S-D 3-Mar-09 9:00 23.10 71.600 9.25 * * Dos Novillos S-E 2-Mar-09 15:50 26.80 67.100 8.30 * * Dos Novillos S-F 3-Mar-09 10:45 24.55 81.950 8.16 * * Lecheria W 4-Mar-09 8:00 26.06 0.053 5.04 7.20 45 Lecheria O 4-Mar-09 8:04 26.11 0.054 0.22 6.32 45 Lecheria I 4-Mar-09 8:12 26.15 0.053 0.32 6.10 64 Lecheria O 4-Mar-09 8:17 26.27 0.055 3.17 6.21 47 Lecheria I-B 4-Mar-09 8:24 25.22 0.068 5.28 6.48 49 Lecheria I-A 4-Mar-09 8:30 26.21 0.063 1.60 6.29 17 Lecheria O 4-Mar-09 8:38 25.33 0.105 0.13 6.25 -29 Lecheria I 4-Mar-09 8:44 25.73 0.209 0.55 6.41 -93 Lecheria O 4-Mar-09 8:48 25.66 0.318 1.55 6.51 -141

Continued 156 Table B1 continued

Temp Conductivity DO Site Location Date Time (˚C) (mS/cm) (mg/L) pH ORP Canal O 4-Mar-09 9:07 26.05 1.424 0.26 7.57 -136 Canal I 4-Mar-09 9:09 26.52 1.690 0.39 7.59 -169 Canal I 4-Mar-09 9:14 26.68 1.487 1.91 7.78 -150 Canal O 4-Mar-09 9:17 26.56 1.497 0.08 7.73 -189 Canal O 4-Mar-09 9:22 25.96 1.717 0.18 7.56 -208 Canal I 4-Mar-09 9:59 25.96 1.980 0.81 7.29 34 Canal O 4-Mar-09 10:03 25.95 2.013 0.35 7.20 -69 Biodigestor O 4-Mar-09 10:06 26.12 2.183 1.41 6.92 -161 Canal I 4-Mar-09 10:11 26.05 1.904 0.99 7.49 -156 Canal O 4-Mar-09 10:14 25.73 1.917 0.11 7.47 -194 Canal I 4-Mar-09 10:16 26.71 2.140 0.49 6.99 -143 Canal O 4-Mar-09 10:21 26.90 2.149 0.12 6.98 -182 Biodigestor I 4-Mar-09 10:26 27.73 0.458 0.05 7.65 -169 Lecheria I-B3 4-Mar-09 10:39 34.74 0.699 0.36 7.11 -128 Lecheria I-B2 4-Mar-09 10:45 27.42 0.738 2.81 6.73 -132 Lecheria I-B1 4-Mar-09 10:48 26.61 0.161 5.62 6.96 -83 Lecheria I-B1 4-Mar-09 10:48 * * * * * Empacadora S-A 4-Mar-09 11:01 26.64 0.125 6.86 7.46 -1 Empacadora S-B 4-Mar-09 11:17 27.26 0.127 6.09 7.68 -11 Empacadora S-C 4-Mar-09 11:20 27.21 0.125 6.97 7.50 -9 Empacadora S-D 4-Mar-09 11:29 27.63 0.128 7.30 7.62 -12 Empacadora S-E 4-Mar-09 11:26 27.51 0.127 7.19 7.68 -26 Empacadora S-F 4-Mar-09 11:23 27.44 0.051 7.40 7.71 -18 Empacadora R 4-Mar-09 11:39 27.59 0.124 6.83 7.67 -23 Sanitario I-A2 4-Mar-09 13:24 29.76 0.052 4.32 6.51 -89 Sanitario O 4-Mar-09 13:30 28.19 0.048 7.40 6.32 31 Papel I-A1 4-Mar-09 13:58 24.52 0.169 4.41 6.60 4 Papel I-A2 4-Mar-09 14:14 25.11 0.086 3.73 6.13 36 Papel I-B 4-Mar-09 14:17 25.57 0.087 5.23 6.33 60 Papel O 4-Mar-09 14:22 25.19 0.105 0.17 6.13 -3 Papel I 4-Mar-09 14:23 25.20 0.104 0.60 6.11 -5 Papel I 4-Mar-09 14:23 * * * * * Papel O 4-Mar-09 14:35 25.86 0.096 0.51 6.32 49 Papel R 4-Mar-09 14:37 25.69 0.096 3.08 6.33 15 BLANK * 4-Mar-09 * * * * * *

157

Appendix C: Raw Methane Emission Data from Tropical Wetlands in Costa Rica

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 E UP I a AM 0 25.0 * 26.0 NL SU06 E UP I b AM 0 25.0 * 26.0 NL SU06 E UP I a PM 0 27.0 * 29.5 NL SU06 E UP I b PM 0 28.0 * 28.2 NL SU06 E UP O a AM 0 27.0 * 26.0 0.3 SU06 E UP O b AM 0 27.0 * 26.0 NL SU06 E UP O a PM 0 27.5 * 28.0 NL SU06 E UP O b PM 0 28.0 * 28.0 NL SU06 E IF I a AM 33 25.5 25.5 27.0 1.4 SU06 E IF I b AM 33 25.5 25.5 26.0 NL SU06 E IF I a PM 33 30.0 27.0 35.0 1.9 SU06 E IF I b PM 33 30.0 28.0 33.0 0.6 SU06 E IF O a AM 67 26.5 26.5 25.3 10.3 SU06 E IF O b AM 66 26.5 26.5 25.5 11.8 SU06 E IF O a PM 67 25.8 25.5 30.0 7.0 SU06 E IF O b PM 66 25.5 25.5 30.0 9.0 SU06 E PF I a AM 30 25.3 25.0 27.0 5.4 SU06 E PF I b AM 25 25.0 25.0 26.5 3.7 SU06 E PF I a PM 25 28.0 * 32.0 4.8 SU06 E PF I b PM 25 28.0 * 30.5 0.6 SU06 E PF O a AM 69 26.0 26.0 26.0 21.8 SU06 E PF O b AM 70 26.0 26.0 26.0 12.1 SU06 E PF O a PM 69 26.0 26.0 30.0 17.9 SU06 E PF O b PM 69 26.0 26.0 30.0 5.5 SU06 PV UP I a AM 0 27.0 * 27.0 NL SU06 PV UP I b AM 0 27.5 * 27.0 NL SU06 PV UP I a PM 0 28.0 * 29.0 NL SU06 PV UP I b PM 0 28.0 * 29.5 NL SU06 PV UP O a AM 0 28.0 * 27.5 NL SU06 PV UP O b AM 0 28.0 * 27.5 NL SU06 PV UP O a PM 0 29.0 * 28.0 NL SU06 PV UP O b PM 0 29.0 * 29.0 NL SU06 PV IF I a AM 2 29.0 30.0 27.0 10.4 SU06 PV IF I b AM 2 30.0 30.5 27.5 11.9 SU06 PV IF I a PM 2 31.5 30.5 33.5 21.2 SU06 PV IF I b PM 2 31.5 31.0 34.5 25.8 SU06 PV IF O a AM 0 29.0 30.0 29.0 1.7 SU06 PV IF O b AM 0 29.0 30.0 29.5 31.2

Table C1. Raw methane emission and environmental property data from tropical wetlands in Costa Rica including EARTH (E), Palo Verde (PV), and La Selva (LS). 158 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 PV IF O a PM 0 31.0 30.0 32.0 4.2 SU06 PV IF O b PM 0 32.0 31.0 33.5 14.1 SU06 PV PF I a AM 30 29.0 * 29.0 80.4 SU06 PV PF I b AM 23 29.0 * 28.5 24.8 SU06 PV PF I a PM 25 30.0 * 36.0 28.3 SU06 PV PF I b PM 19 30.0 * 35.0 18.9 SU06 PV PF O a AM 10 29.5 * 31.0 74.8 SU06 PV PF O b AM 11 29.5 * 31.0 178.0 SU06 PV PF O a PM 11 31.0 * 32.0 25.1 SU06 PV PF O b PM 8 31.0 * 32.0 558.6 SU06 LS UP I a AM 0 25.0 * 23.5 NL SU06 LS UP I b AM 0 25.0 * 24.0 -0.8 SU06 LS UP I a PM 0 26.0 * 27.0 NL SU06 LS UP I b PM 0 26.0 * 27.0 NL SU06 LS UP O a AM 0 25.0 * 24.0 NL SU06 LS UP O b AM 0 25.0 * 24.0 NL SU06 LS UP O a PM 0 26.0 * 27.0 0.6 SU06 LS UP O b PM 0 26.0 * 27.0 NL SU06 LS IF I a AM 0 25.0 * 25.0 17.4 SU06 LS IF I b AM 0 25.0 * 24.5 24.8 SU06 LS IF I a PM 0 26.0 * 27.0 44.0 SU06 LS IF I b PM 0 26.0 * 28.0 22.8 SU06 LS IF O a AM 0 25.0 26.0 24.0 NL SU06 LS IF O b AM 0 25.0 26.0 23.3 NL SU06 LS IF O a PM 0 26.0 26.0 27.0 NL SU06 LS IF O b PM 0 26.0 26.0 27.0 NL SU06 LS PF I a AM 9 26.0 * 24.0 NL SU06 LS PF I b AM 11 26.0 * 25.0 NL SU06 LS PF I a PM 18 26.5 * 28.0 16.7 SU06 LS PF I b PM 8 26.5 * 28.0 68.9 SU06 LS PF O a AM 0 25.0 26.0 23.5 NL SU06 LS PF O b AM 0 25.0 26.0 24.0 NL SU06 LS PF O a PM 0 26.0 26.0 28.0 NL SU06 LS PF O b PM 0 26.0 26.0 28.0 NL WI07 E UP I a AM 0 24.5 23.8 26.0 NL WI07 E UP I b AM 0 24.5 23.8 26.0 NL WI07 E UP I a PM 0 25.0 25.0 29.0 NL WI07 E UP I b PM 0 25.0 25.0 30.0 NL WI07 E UP O a AM 0 25.0 25.0 27.0 0 WI07 E UP O b AM 0 25.0 25.0 27.0 NL WI07 E UP O a PM 0 27.0 26.0 31.0 NL WI07 E UP O b PM 0 27.0 26.0 33.0 NL WI07 E IF I a AM 33 24.5 24.5 24.0 NL WI07 E IF I b AM 33 24.5 24.5 24.8 0 WI07 E IF I a PM 33 26.0 25.3 33.0 1 WI07 E IF I b PM 33 26.0 25.3 34.5 NL WI07 E IF O a AM 68 24.0 24.0 27.5 1 WI07 E IF O b AM 67 24.0 24.0 27.3 1 WI07 E IF O a PM 67 24.0 24.0 33.0 1 WI07 E IF O b PM 67 24.0 24.0 34.0 3

Continued 159 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) WI07 E PF I a AM 42 24.0 24.0 25.0 1 WI07 E PF I b AM 30 24.0 24.0 25.0 NL WI07 E PF I a PM 25 25.0 24.8 29.0 4 WI07 E PF I b PM 25 25.0 24.8 29.0 1 WI07 E PF O a AM 70 24.0 24.0 25.0 5 WI07 E PF O b AM 69 24.0 24.0 25.0 3 WI07 E PF O a PM 70 24.0 24.0 30.3 6 WI07 E PF O b PM 70 24.0 24.0 31.0 2 WI07 PV UP I a AM 0 30.5 * 32.0 NL WI07 PV UP I b AM 0 30.5 * 32.0 NL WI07 PV UP I a PM 0 31.0 * 33.0 NL WI07 PV UP I b PM 0 31.0 * 33.0 NL WI07 PV UP O a AM 0 30.0 * 34.0 NL WI07 PV UP O b AM 0 30.0 * 34.0 NL WI07 PV UP O a PM 0 32.0 * 33.5 NL WI07 PV UP O b PM 0 32.0 * 33.5 NL WI07 PV IF I a AM 28 26.3 26.5 31.0 294 WI07 PV IF I b AM 26 26.3 26.5 31.0 50 WI07 PV IF I a PM 23 27.0 27.0 34.8 45 WI07 PV IF I b PM 24 27.0 27.0 32.0 84 WI07 PV IF O a AM 27 26.5 27.0 29.0 51 WI07 PV IF O b AM 25 26.5 27.0 32.0 NL WI07 PV IF O a PM 27 27.5 27.0 37.3 NL WI07 PV IF O b PM 24 27.5 27.0 32.8 35 WI07 PV PF I a AM 60 26.0 26.5 32.0 NL WI07 PV PF I b AM 55 26.0 26.5 32.5 35 WI07 PV PF I a PM 53 26.0 26.5 34.0 6 WI07 PV PF I b PM 47 26.0 26.5 32.0 5 WI07 PV PF O a AM 54 26.5 26.5 30.5 79 WI07 PV PF O b AM 54 26.5 26.5 28.0 39 WI07 PV PF O a PM 55 27.0 27.0 36.0 2 WI07 PV PF O b PM 67 27.0 27.0 33.0 27 WI07 LS UP I a AM 0 23.0 23.5 23.0 NL WI07 LS UP I b AM 0 23.0 23.5 23.0 NL WI07 LS UP I a PM 0 23.5 24.0 25.0 NL WI07 LS UP I b PM 0 23.5 24.0 25.3 NL WI07 LS UP O a AM 0 22.8 23.0 23.5 0 WI07 LS UP O b AM 0 22.8 23.0 23.0 NL WI07 LS UP O a PM 0 23.5 23.8 27.0 NL WI07 LS UP O b PM 0 23.5 23.8 27.0 NL WI07 LS IF I a AM 15 24.0 24.3 23.0 2 WI07 LS IF I b AM 15 24.0 24.3 23.5 40 WI07 LS IF I a PM 16 24.0 24.3 25.5 9 WI07 LS IF I b PM 16 24.0 24.3 25.5 4 WI07 LS IF O a AM 0 23.0 23.3 24.0 0 WI07 LS IF O b AM 0 23.0 23.3 24.0 NL WI07 LS IF O a PM 0 24.0 24.0 27.0 0 WI07 LS IF O b PM 0 24.0 24.0 27.0 NL WI07 LS PF I a AM 36 24.0 25.3 24.0 10 WI07 LS PF I b AM 36 24.0 24.3 24.0 18

Continued 160 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) WI07 LS PF I a PM 40 24.0 24.3 25.5 12 WI07 LS PF I b PM 40 24.0 24.3 25.5 8 WI07 LS PF O a AM 0 23.8 24.0 25.0 0 WI07 LS PF O b AM 0 23.8 24.0 25.0 NL WI07 LS PF O a PM 0 24.5 24.0 26.5 0 WI07 LS PF O b PM 0 24.5 24.0 26.5 NL SP07 E UP I a AM 0 24.8 * 26.0 NL SP07 E UP I b AM 0 24.8 * 25.0 NL SP07 E UP I a PM 0 25.0 * 30.0 -1 SP07 E UP I b PM 0 25.0 * 30.0 NL SP07 E UP O a AM 0 26.0 * 28.0 NL SP07 E UP O b AM 0 26.0 * 29.0 NL SP07 E UP O a PM 0 26.0 * 28.0 NL SP07 E UP O b PM 0 26.0 * 28.0 NL SP07 E IF I a AM 33 24.0 24.0 25.5 NL SP07 E IF I b AM 33 24.5 24.5 25.0 NL SP07 E IF I a PM 33 27.8 26.0 33.5 18 SP07 E IF I b PM 33 27.0 25.0 33.0 10 SP07 E IF O a AM 66 27.0 26.0 34.0 16 SP07 E IF O b AM 66 27.0 26.0 33.0 4 SP07 E IF O a PM 66 32.0 31.5 31.0 0 SP07 E IF O b PM 66 32.0 31.5 32.0 0 SP07 E PF I a AM 25 26.0 26.0 25.0 1 SP07 E PF I b AM 25 26.0 26.0 27.0 2 SP07 E PF I a PM 25 27.0 26.0 34.0 7 SP07 E PF I b PM 25 27.0 26.0 32.0 7 SP07 E PF O a AM 65 25.0 25.0 31.0 7 SP07 E PF O b AM 65 25.0 25.0 32.0 6 SP07 E PF O a PM 65 25.0 24.8 30.0 1 SP07 E PF O b PM 65 25.0 24.8 28.0 NL SP07 PV UP I a AM 0 26.5 * 27.0 NL SP07 PV UP I b AM 0 26.5 * 26.5 NL SP07 PV UP I a PM 0 30.5 * 31.0 -3 SP07 PV UP I b PM 0 30.5 * 31.0 0 SP07 PV UP O a AM 0 27.0 * 29.0 NL SP07 PV UP O b AM 0 27.0 * 29.0 0 SP07 PV UP O a PM 0 31.0 * 32.0 NL SP07 PV UP O b PM 0 31.0 * 33.0 -1 SP07 PV IF I a AM 0 26.8 27.5 27.3 25 SP07 PV IF I b AM 0 27.5 27.5 26.8 7 SP07 PV IF I a PM 0 32.0 28.0 33.0 8 SP07 PV IF I b PM 0 32.0 28.0 32.0 21 SP07 PV IF O a AM 0 26.0 27.0 28.0 16 SP07 PV IF O b AM 0 26.0 27.0 28.0 26 SP07 PV IF O a PM 0 30.0 28.0 38.0 NL SP07 PV IF O b PM 0 30.0 28.0 39.0 4 SP07 PV PF I a AM 0 26.3 26.5 25.5 NL SP07 PV PF I b AM 0 26.3 26.5 25.0 10 SP07 PV PF I a PM 0 29.0 27.5 37.0 0 SP07 PV PF I b PM 0 29.0 27.5 36.0 1

Continued 161 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SP07 PV PF O a AM 0 25.5 26.5 28.0 NL SP07 PV PF O b AM 0 25.5 26.5 28.0 NL SP07 PV PF O a PM 0 30.0 27.0 35.0 NL SP07 PV PF O b PM 0 30.0 27.0 36.0 7 SP07 LS UP I a AM 0 23.5 * 24.0 NL SP07 LS UP I b AM 0 23.5 * 25.0 NL SP07 LS UP I a PM 0 26.5 * 28.5 NL SP07 LS UP I b PM 0 26.5 * 26.0 NL SP07 LS UP O a AM 0 25.5 * 27.0 NL SP07 LS UP O b AM 0 25.5 * 27.0 NL SP07 LS UP O a PM 0 26.0 * 28.0 1 SP07 LS UP O b PM 0 26.0 * 27.0 1 SP07 LS IF I a AM 0 25.0 26.0 24.0 1 SP07 LS IF I b AM 0 25.0 26.0 23.0 3 SP07 LS IF I a PM 0 25.0 24.0 29.0 NL SP07 LS IF I b PM 0 25.0 24.0 29.0 1 SP07 LS IF O a AM 0 25.0 24.5 26.0 NL SP07 LS IF O b AM 0 25.0 24.5 28.0 NL SP07 LS IF O a PM 0 26.0 26.4 26.0 NL SP07 LS IF O b PM 0 26.0 26.4 26.0 NL SP07 LS PF I a AM 0 24.5 25.0 23.0 6 SP07 LS PF I b AM 0 24.5 25.0 22.0 11 SP07 LS PF I a PM 0 26.0 25.0 27.5 5 SP07 LS PF I b PM 0 26.0 25.0 27.9 3 SP07 LS PF O a AM 0 24.5 24.8 28.0 0 SP07 LS PF O b AM 0 24.5 24.8 30.0 -1 SP07 LS PF O a PM 0 25.0 24.5 26.0 1 SP07 LS PF O b PM 0 25.0 24.5 27.0 NL SU07 E UP I a AM 0 25.0 * 27.3 1 SU07 E UP I b AM 0 25.0 * 27.0 NL SU07 E UP I a PM 0 26.5 * 29.5 NL SU07 E UP I b PM 0 26.5 * 30.0 NL SU07 E UP O a AM 0 25.8 * 26.3 NL SU07 E UP O b AM 0 26.0 * 26.0 NL SU07 E UP O a PM 0 27.0 * 29.8 NL SU07 E UP O b PM 0 27.0 * 35.5 NL SU07 E IF I a AM 34 25.0 25.5 25.5 NL SU07 E IF I b AM 34 25.0 25.5 25.5 NL SU07 E IF I a PM 34 28.5 28.0 41.5 NL SU07 E IF I b PM 34 28.5 27.0 35.0 17 SU07 E IF O a AM 68 25.0 25.0 27.0 74 SU07 E IF O b AM 68 25.0 25.0 28.0 414 SU07 E IF O a PM 67 25.5 25.0 30.2 59 SU07 E IF O b PM 69 25.8 25.0 34.0 92 SU07 E PF I a AM 30 24.8 24.8 25.0 27 SU07 E PF I b AM 30 24.8 24.8 24.0 NL SU07 E PF I a PM 30 26.5 26.3 31.8 20 SU07 E PF I b PM 30 26.5 26.3 30.5 -6 SU07 E PF O a AM 67 24.8 24.5 25.3 37 SU07 E PF O b AM 67 24.8 25.0 26.0 40

Continued 162 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU07 E PF O a PM 66 28.0 27.0 32.5 25 SU07 E PF O b PM 66 27.0 27.0 32.5 22 SU07 PV UP I a AM 0 25.8 * 26.0 0 SU07 PV UP I b AM 0 25.8 * 25.0 0 SU07 PV UP I a PM 0 28.3 * 27.0 NL SU07 PV UP I b PM 0 28.3 * 26.0 NL SU07 PV UP O a AM 0 25.5 * 27.0 0 SU07 PV UP O b AM 0 25.5 * 29.0 NL SU07 PV UP O a PM 0 27.5 * 28.0 NL SU07 PV UP O b PM 0 27.5 * 28.0 NL SU07 PV IF I a AM 56 27.3 * 33.0 44 SU07 PV IF I b AM 64 27.3 * 30.0 NL SU07 PV IF I a PM * * * * * SU07 PV IF I b PM * * * * * SU07 PV IF O a AM 64 26.0 * 32.0 15 SU07 PV IF O b AM 69 26.0 * 31.0 16 SU07 PV IF O a PM 64 31.5 * 37.5 NL SU07 PV IF O b PM 70 30.5 * 37.0 13 SU07 PV PF I a AM 80 28.0 * 35.5 33 SU07 PV PF I b AM 82 28.5 * 36.0 NL SU07 PV PF I a PM 79 30.5 * 36.0 12 SU07 PV PF I b PM 81 32.0 * 38.0 47 SU07 PV PF O a AM 69 26.5 * 33.5 108 SU07 PV PF O b AM 74 27.0 * 32.0 NL SU07 PV PF O a PM 72 30.0 * 39.0 22 SU07 PV PF O b PM 72 30.5 * 39.0 33 SU07 LS UP I a AM 0 25.0 * 24.3 NL SU07 LS UP I b AM 0 25.1 * 24.5 NL SU07 LS UP I a PM 0 25.0 * 26.5 0 SU07 LS UP I b PM 0 25.0 * 27.0 NL SU07 LS UP O a AM 0 24.5 * 25.8 0 SU07 LS UP O b AM 0 24.5 * 24.8 0 SU07 LS UP O a PM 0 24.0 * 25.5 0 SU07 LS UP O b PM 0 24.0 * 26.3 0 SU07 LS IF I a AM 3 24.0 24.3 24.0 NL SU07 LS IF I b AM 4 24.0 24.3 25.0 NL SU07 LS IF I a PM 1 24.8 24.8 27.3 -4 SU07 LS IF I b PM 1 24.5 24.3 27.5 NL SU07 LS IF O a AM 0 23.8 24.0 25.0 NL SU07 LS IF O b AM 0 23.8 24.0 24.8 -1 SU07 LS IF O a PM 0 24.3 24.3 25.5 NL SU07 LS IF O b PM 0 25.0 25.0 25.0 NL SU07 LS PF I a AM 37 25.0 25.0 25.0 401 SU07 LS PF I b AM 37 25.0 25.0 25.0 278 SU07 LS PF I a PM 33 25.3 25.3 27.0 66 SU07 LS PF I b PM 33 25.3 25.3 27.0 128 SU07 LS PF O a AM 0 25.0 24.8 25.8 NL SU07 LS PF O b AM 0 25.0 24.8 26.5 NL SU07 LS PF O a PM 0 25.0 25.0 25.0 0 SU07 LS PF O b PM 0 25.0 25.0 26.0 0

Continued 163 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU08 E UP I a AM 0 26.0 * 26.2 -1 SU08 E UP I b AM 0 26.0 * 25.0 0 SU08 E UP I a PM 0 27.0 * 26.8 NL SU08 E UP I b PM 0 27.0 * 25.5 NL SU08 E UP O a AM 0 24.5 * 26.8 NL SU08 E UP O b AM 0 24.5 * 27.0 0 SU08 E UP O a PM 0 25.3 * 30.0 NL SU08 E UP O b PM 0 25.3 * 30.5 NL SU08 E IF I a AM 34 23.3 23.5 27.0 -5 SU08 E IF I b AM 34 23.3 23.5 26.0 28 SU08 E IF I a PM 34 26.0 24.5 31.2 NL SU08 E IF I b PM 34 26.0 25.0 31.8 NL SU08 E IF O a AM 68 23.1 23.1 26.2 6 SU08 E IF O b AM 70 23.3 23.3 25.9 7 SU08 E IF O a PM 68 24.0 24.0 28.9 9 SU08 E IF O b PM 70 24.0 24.0 29.2 4 SU08 E PF I a AM 36 26.0 26.0 25.0 1 SU08 E PF I b AM 36 26.0 26.0 24.0 -4 SU08 E PF I a PM 36 25.0 24.5 28.4 1 SU08 E PF I b PM 36 25.0 24.5 28.0 1 SU08 E PF O a AM 72 23.5 23.5 28.1 17 SU08 E PF O b AM 69 23.5 23.5 27.0 17 SU08 E PF O a PM 70 24.0 23.8 28.9 13 SU08 E PF O b PM 70 24.1 24.0 30.0 13 SU08 PV UP I a AM 0 26.5 * 24.9 NL SU08 PV UP I b AM 0 26.5 * 25.3 NL SU08 PV UP I a PM 0 27.3 * 25.0 1 SU08 PV UP I b PM 0 27.3 * 25.5 NL SU08 PV UP O a AM 0 28.0 * 28.5 NL SU08 PV UP O b AM 0 28.0 * 27.5 NL SU08 PV UP O a PM 0 28.0 * 26.0 NL SU08 PV UP O b PM 0 28.0 * 25.0 NL SU08 PV IF I a AM 0 28.0 * 28.0 35 SU08 PV IF I b AM 0 28.0 * 28.0 60 SU08 PV IF I a PM 0 29.0 * 30.0 4 SU08 PV IF I b PM 0 29.0 * 31.8 21 SU08 PV IF O a AM 62 29.5 * 29.8 4 SU08 PV IF O b AM 62 29.5 * 30.0 6 SU08 PV IF O a PM 46 30.0 * 31.0 6 SU08 PV IF O b PM 46 30.0 * 32.0 4 SU08 PV PF I a AM 0 28.0 * 26.0 10 SU08 PV PF I b AM 0 28.0 * 25.0 5 SU08 PV PF I a PM 0 29.0 * 28.5 6 SU08 PV PF I b PM 0 29.0 * 29.0 2 SU08 PV PF O a AM 71 29.5 * 29.5 32 SU08 PV PF O b AM 71 29.5 * 30.0 12 SU08 PV PF O a PM 70 30.0 * 35.0 13 SU08 PV PF O b PM 70 30.0 * 33.5 10 SU08 LS UP I a AM 0 26.0 * 25.0 1 SU08 LS UP I b AM 0 26.0 * 23.0 -1

Continued 164 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU08 LS UP I a PM 0 26.0 * 27.0 NL SU08 LS UP I b PM 0 26.0 * 27.5 NL SU08 LS UP O a AM 0 26.0 * 24.0 NL SU08 LS UP O b AM 0 26.0 * 25.0 NL SU08 LS UP O a PM 0 25.2 26.1 27.5 NL SU08 LS UP O b PM 0 25.2 26.1 27.5 0 SU08 LS IF I a AM 62 25.8 * 26.0 9 SU08 LS IF I b AM 62 25.8 * 26.0 1 SU08 LS IF I a PM 57 25.5 * 28.0 4 SU08 LS IF I b PM 57 25.5 * 27.5 7 SU08 LS IF O a AM 0 24.0 24.0 24.8 NL SU08 LS IF O b AM 0 24.0 24.0 24.8 NL SU08 LS IF O a PM 0 24.0 24.2 25.0 NL SU08 LS IF O b PM 0 24.0 24.2 25.5 NL SU08 LS PF I a AM 79 26.0 * 26.0 159 SU08 LS PF I b AM 79 26.0 * 25.5 16 SU08 LS PF I a PM 76 24.8 * 27.0 6 SU08 LS PF I b PM 76 24.8 * 27.0 75 SU08 LS PF O a AM 16 24.8 25.0 25.0 1 SU08 LS PF O b AM 10 24.8 25.0 24.2 2 SU08 LS PF O a PM 16 24.8 25.0 26.0 5 SU08 LS PF O b PM 10 24.8 25.0 25.3 2 WI09 E UP I a AM 0 23.0 * 25.0 0 WI09 E UP I b AM 0 23.0 * 25.0 NL WI09 E UP I a PM 0 24.0 * 24.0 0 WI09 E UP I b PM 0 24.0 * 23.5 NL WI09 E UP O a AM 0 25.5 * 27.0 0 WI09 E UP O b AM 0 26.0 * 25.5 0 WI09 E UP O a PM 0 25.0 * 27.0 NL WI09 E UP O b PM 0 25.0 * 27.0 NL WI09 E IF I a AM 36 24.0 24.8 22.0 NL WI09 E IF I b AM 40 24.0 24.8 22.5 5 WI09 E IF I a PM 55 24.8 24.8 25.0 NL WI09 E IF I b PM 55 25.0 25.0 24.5 -5 WI09 E IF O a AM 72 24.0 * 28.0 2 WI09 E IF O b AM 71 24.0 * 28.5 2 WI09 E IF O a PM 71 23.5 * 28.0 1 WI09 E IF O b PM 73 23.5 * 28.0 1 WI09 E PF I a AM 30 23.0 23.0 23.5 7 WI09 E PF I b AM 30 23.0 23.0 24.5 NL WI09 E PF I a PM 59 24.0 * 25.0 NL WI09 E PF I b PM 48 24.0 * 25.0 1 WI09 E PF O a AM 77 23.8 * 27.0 1 WI09 E PF O b AM 76 23.8 * 27.0 3 WI09 E PF O a PM 78 23.5 * 28.0 1 WI09 E PF O b PM 76 23.8 * 27.5 2 WI09 PV UP I a AM 0 25.8 * 28.5 NL WI09 PV UP I b AM 0 25.8 * 29.3 NL WI09 PV UP I a PM 0 28.8 * 29.5 0 WI09 PV UP I b PM 0 28.8 * 29.0 NL

Continued 165 Table C1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) WI09 PV UP O a AM 0 31.5 * 33.0 NL WI09 PV UP O b AM 0 31.5 * 32.5 1 WI09 PV UP O a PM 0 30.5 * 32.0 NL WI09 PV UP O b PM 0 30.5 * 31.0 0 WI09 PV IF I a AM 0 24.0 * 30.0 NL WI09 PV IF I b AM 0 24.0 * 30.0 14 WI09 PV IF I a PM 0 27.0 * 34.0 NL WI09 PV IF I b PM 0 27.0 * 34.0 6 WI09 PV IF O a AM 20 23.0 24.0 31.0 111 WI09 PV IF O b AM 20 24.0 24.0 31.0 3 WI09 PV IF O a PM 30 25.0 * 30.0 490 WI09 PV IF O b PM 27 24.5 * 30.5 5 WI09 PV PF I a AM 25 23.0 * 33.0 1 WI09 PV PF I b AM 25 23.0 * 32.8 2 WI09 PV PF I a PM 25 23.3 * 35.0 3 WI09 PV PF I b PM 25 23.3 * 39.5 3 WI09 PV PF O a AM 11 25.0 24.8 31.0 119 WI09 PV PF O b AM 13 24.0 24.0 30.0 6 WI09 PV PF O a PM 10 25.0 * 34.0 16 WI09 PV PF O b PM 25 25.5 * 35.0 8 WI09 LS UP I a AM 0 24.0 * 24.0 NL WI09 LS UP I b AM 0 24.0 * 24.0 0 WI09 LS UP I a PM 0 24.0 * 24.5 NL WI09 LS UP I b PM 0 24.0 * 25.0 0 WI09 LS UP O a AM 40 23.5 * 24.0 NL WI09 LS UP O b AM 60 23.5 * 24.0 NL WI09 LS UP O a PM 8 25.0 * 24.0 0 WI09 LS UP O b PM 12 25.0 * 24.0 NL WI09 LS IF I a AM 23 24.0 * 23.0 44 WI09 LS IF I b AM 23 24.0 * 24.0 69 WI09 LS IF I a PM 35 24.8 * 26.0 340 WI09 LS IF I b PM 35 24.8 * 26.0 38 WI09 LS IF O a AM 0 23.0 23.8 23.5 NL WI09 LS IF O b AM 0 23.0 23.8 24.5 0 WI09 LS IF O a PM 0 23.0 23.0 24.8 0 WI09 LS IF O b PM 0 23.0 23.0 23.8 0 WI09 LS PF I a AM 68 24.0 * 24.7 21 WI09 LS PF I b AM 68 24.0 * 25.0 27 WI09 LS PF I a PM 65 24.5 * 26.0 262 WI09 LS PF I b PM 65 24.5 * 26.0 87 WI09 LS PF O a AM 2 25.0 25.0 23.0 1 WI09 LS PF O b AM 2 25.0 25.0 24.0 0 WI09 LS PF O a PM 2 25.0 25.0 23.5 5 WI09 LS PF O b PM 2 25.0 25.0 25.0 1

166

Appendix D: Raw Methane Emission Data from Temperate Wetlands in Ohio

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 ORW1 UP O b PM 0.00 23.5 23.0 24.0 NL SU06 ORW1 IF I a AM 0.04 24.0 24.5 25.0 12 SU06 ORW1 IF I b AM 0.03 24.0 24.0 24.8 5 SU06 ORW1 IF I a PM 0.04 25.0 25.0 24.0 10 SU06 ORW1 IF I b PM 0.05 25.0 25.0 24.0 2 SU06 ORW1 IF O a AM 0.03 25.0 26.0 25.0 1 SU06 ORW1 IF O b AM 0.03 25.0 26.0 25.0 NL SU06 ORW1 IF O a PM 0.04 23.5 23.5 26.0 4 AU06 ORW1 UP O b PM 0.00 6.0 * 14.0 NL AU06 ORW1 IF I a AM 0.04 4.5 4.2 6.9 NL AU06 ORW1 IF I b AM 0.05 4.5 4.2 8.2 0 AU06 ORW1 IF I a PM 0.06 6.0 6.0 12.0 1 AU06 ORW1 IF I b PM 0.03 6.0 6.0 15.0 0 AU06 ORW1 IF O a AM 0.20 6.2 6.3 15.0 0 AU06 ORW1 IF O b AM 0.18 6.2 6.8 12.2 0 AU06 ORW1 IF O a PM 0.20 6.5 * 14.0 NL SU07 ORW1 UP O b PM 0.00 24.0 * 25.8 NL SU07 ORW1 IF I a AM 0.00 21.0 * 21.5 NL SU07 ORW1 IF I b AM 0.00 21.0 * 21.5 NL SU07 ORW1 IF I a PM 0.00 22.0 21.5 28.0 NL SU07 ORW1 IF I b PM 0.00 22.0 1.5 28.5 NL SU07 ORW1 IF O a AM 0.05 23.0 24.0 20.5 2 SU07 ORW1 IF O b AM 0.03 23.0 24.0 20.5 4 SU07 ORW1 IF O a PM 0.05 26.0 25.0 28.5 NL AU07 ORW1 UP O b PM 0.00 5.8 * 10.0 NL AU07 ORW1 IF I a AM 0.09 2.8 3.5 -2.3 NL AU07 ORW1 IF I b AM 0.09 3.0 3.8 -2.3 0 AU07 ORW1 IF I a PM 0.06 3.0 * 10.0 NL AU07 ORW1 IF I b PM 0.05 3.0 * 10.0 0 AU07 ORW1 IF O a AM 0.22 1.0 * -2.0 NL AU07 ORW1 IF O b AM 0.21 1.0 * -2.3 0 AU07 ORW1 IF O a PM 0.20 3.0 * 14.5 NL WI08 ORW1 UP O b PM 0.00 6.9 7.0 10.2 NL WI08 ORW1 IF I a AM 0.13 1.5 * 5.8 NL WI08 ORW1 IF I b AM 0.11 1.0 * 5.3 0 WI08 ORW1 IF I a PM 0.11 2.0 1.1 10.5 NL WI08 ORW1 IF I b PM 0.11 1.5 1.8 11.2 NL WI08 ORW1 IF O a AM 0.22 3.0 * 5.3 NL

Table D1. Raw methane emission and environmental property data from temperate wetlands in Ohio including Olentangy River Wetland 1 (ORW1), Olentangy River Wetland 2 (ORW2), and Old Woman Creek (OWC). 167 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) WI08 ORW1 IF O b AM 0.23 3.5 * 5.0 NL WI08 ORW1 IF O a PM 0.26 2.5 2.5 10.0 NL SP08 ORW1 UP O b PM 0.00 14.0 13.5 17.0 NL SP08 ORW1 IF I a AM 0.00 10.0 11.0 8.0 NL SP08 ORW1 IF I b AM 0.00 10.0 11.0 8.0 -1 SP08 ORW1 IF I a PM 0.00 13.0 13.0 19.0 NL SP08 ORW1 IF I b PM 0.00 12.8 13.0 18.5 NL SP08 ORW1 IF O a AM 0.00 9.8 11.3 11.0 -2 SP08 ORW1 IF O b AM 0.00 9.8 11.3 12.0 NL SP08 ORW1 IF O a PM 0.00 14.5 13.0 20.0 NL SU08 ORW1 UP O b PM 0.00 22.0 * 0.0 NL SU08 ORW1 IF I a AM 0.00 17.0 19.0 17.5 11 SU08 ORW1 IF I b AM 0.00 19.0 19.0 16.8 9 SU08 ORW1 IF I a PM 0.00 * * 34.2 NL SU08 ORW1 IF I b PM 0.00 * * 34.2 NL SU08 ORW1 IF O a AM 0.09 * * 20.2 NL SU08 ORW1 IF O b AM 0.09 * * 20.0 NL SU08 ORW1 IF O a PM 0.09 22.0 22.0 0.0 4 SU06 ORW1 IF O b PM 0.06 23.5 23.5 24.0 2 SU06 ORW1 PF I a AM 0.22 25.0 25.0 28.0 0 SU06 ORW1 PF I b AM 0.22 25.0 25.0 28.5 0 SU06 ORW1 PF I a PM 0.22 26.0 25.5 25.5 0 SU06 ORW1 PF I b PM 0.21 26.0 25.5 28.0 0 SU06 ORW1 PF O a AM 0.15 25.0 25.0 25.0 0 SU06 ORW1 PF O b AM 0.15 25.0 25.0 26.0 0 SU06 ORW1 PF O a PM 0.11 26.5 26.8 29.0 0 AU06 ORW1 IF O b PM 0.21 6.5 * 16.0 NL AU06 ORW1 PF I a AM 0.25 7.0 * 11.5 0 AU06 ORW1 PF I b AM 0.23 7.0 * 11.0 1 AU06 ORW1 PF I a PM 0.25 8.0 8.0 14.0 0 AU06 ORW1 PF I b PM 0.25 8.0 8.0 14.0 NL AU06 ORW1 PF O a AM 0.27 5.5 * 15.0 0 AU06 ORW1 PF O b AM 0.27 5.5 * 16.0 0 AU06 ORW1 PF O a PM 0.23 7.0 * 14.0 NL SU07 ORW1 IF O b PM 0.03 26.0 25.0 27.0 5 SU07 ORW1 PF I a AM 0.10 24.0 * 28.0 NL SU07 ORW1 PF I b AM 0.10 24.0 * 28.0 NL SU07 ORW1 PF I a PM 0.10 25.0 * 27.0 3 SU07 ORW1 PF I b PM 0.10 25.0 * 27.0 NL SU07 ORW1 PF O a AM 0.14 24.8 25.0 22.5 NL SU07 ORW1 PF O b AM 0.14 24.8 25.0 22.5 24 SU07 ORW1 PF O a PM 0.14 26.5 26.0 36.5 39 AU07 ORW1 IF O b PM 0.21 2.5 * 14.5 NL AU07 ORW1 PF I a AM 0.27 4.0 * -1.5 NL AU07 ORW1 PF I b AM 0.27 4.0 * -2.0 NL AU07 ORW1 PF I a PM 0.23 7.0 7.5 12.0 NL AU07 ORW1 PF I b PM 0.39 1.5 * 12.0 0 AU07 ORW1 PF O a AM 0.39 1.5 * 0.0 1 AU07 ORW1 PF O b AM 0.39 1.5 * 0.0 1 AU07 ORW1 PF O a PM 0.40 5.5 * 10.0 NL

Continued 168 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) WI08 ORW1 IF O b PM 0.26 2.5 2.5 10.0 NL WI08 ORW1 PF I a AM 0.33 6.0 * 7.0 0 WI08 ORW1 PF I b AM 0.33 6.0 * 7.0 NL WI08 ORW1 PF I a PM 0.40 6.5 * 12.0 NL WI08 ORW1 PF I b PM 0.40 6.5 * 12.0 NL WI08 ORW1 PF O a AM 0.46 1.0 * 6.3 NL WI08 ORW1 PF O b AM 0.46 1.0 * 7.0 NL WI08 ORW1 PF O a PM 0.46 7.0 * 11.0 NL SP08 ORW1 IF O b PM 0.00 14.5 13.0 21.0 1 SP08 ORW1 PF I a AM 0.00 11.5 13.5 15.5 NL SP08 ORW1 PF I b AM 0.00 10.5 12.3 13.0 NL SP08 ORW1 PF I a PM 0.00 18.0 16.3 21.2 NL SP08 ORW1 PF I b PM 0.00 17.5 16.0 20.8 NL SP08 ORW1 PF O a AM 0.00 11.0 13.0 17.3 1 SP08 ORW1 PF O b AM 0.00 11.5 13.0 15.3 3 SP08 ORW1 PF O a PM 0.00 16.0 14.5 19.0 1 SU08 ORW1 IF O b PM 0.09 23.0 22.0 0.0 11 SU08 ORW1 PF I a AM 0.14 22.0 23.0 17.8 NL SU08 ORW1 PF I b AM 0.14 22.0 23.0 17.5 2 SU08 ORW1 PF I a PM 0.17 23.5 23.1 40.5 10 SU08 ORW1 PF I b PM 0.17 23.5 23.1 36.0 17 SU08 ORW1 PF O a AM 0.17 21.0 23.0 18.0 3 SU08 ORW1 PF O b AM 0.17 21.0 23.0 18.0 NL SU08 ORW1 PF O a PM 0.18 22.3 22.5 0.0 NL SU06 OWC PF O b PM 0.24 33.5 33.5 35.0 7 SU06 ORW1 UP I a AM 0.00 23.0 23.0 26.0 NL SU06 ORW1 UP I b AM 0.00 23.0 23.0 25.0 NL SU06 ORW1 UP I a PM 0.00 23.0 23.0 24.0 NL SU06 ORW1 UP I b PM 0.00 23.1 23.1 24.0 NL SU06 ORW1 UP O a AM 0.00 25.0 25.0 27.0 NL SU06 ORW1 UP O b AM 0.00 25.0 25.0 27.0 NL SU06 ORW1 UP O a PM 0.00 24.2 24.0 25.3 0 AU06 OWC PF O b PM 0.20 6.5 7.0 7.0 NL AU06 ORW1 UP I a AM 0.00 6.0 * 9.0 NL AU06 ORW1 UP I b AM 0.00 6.0 * 9.0 0 AU06 ORW1 UP I a PM 0.00 7.0 * 13.0 0 AU06 ORW1 UP I b PM 0.00 6.0 * 13.0 0 AU06 ORW1 UP O a AM 0.00 6.0 * 17.0 0 AU06 ORW1 UP O b AM 0.00 6.0 * 17.0 NL AU06 ORW1 UP O a PM 0.00 6.0 * 15.0 NL SU07 OWC PF O b PM 0.46 27.3 * 41.5 NL SU07 ORW1 UP I a AM 0.00 20.0 * 20.0 NL SU07 ORW1 UP I b AM 0.00 20.0 * 20.0 NL SU07 ORW1 UP I a PM 0.00 22.0 * 27.0 NL SU07 ORW1 UP I b PM 0.00 22.0 * 27.0 NL SU07 ORW1 UP O a AM 0.00 22.0 * 23.0 0 SU07 ORW1 UP O b AM 0.00 22.0 * 24.0 NL SU07 ORW1 UP O a PM 0.00 24.0 * 25.5 NL SU07 LS PF O b PM 0.00 25.0 25.0 26.0 0 AU07 ORW1 UP I a AM 0.00 3.0 * 2.3 0

Continued 169 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) AU07 ORW1 UP I b AM 0.00 5.0 * 3.0 NL AU07 ORW1 UP I a PM 0.00 5.0 * 8.9 NL AU07 ORW1 UP I b PM 0.00 5.3 * 10.1 NL AU07 ORW1 UP O a AM 0.00 3.0 * -3.0 NL AU07 ORW1 UP O b AM 0.00 3.0 * -3.0 0 AU07 ORW1 UP O a PM 0.00 5.5 * 10.0 NL WI08 OWC PF O b PM 0.21 1.0 * 12.0 2 WI08 ORW1 UP I a AM 0.00 6.8 7.2 5.5 -1 WI08 ORW1 UP I b AM 0.00 6.1 6.0 5.9 NL WI08 ORW1 UP I a PM 0.00 8.0 * 9.8 NL WI08 ORW1 UP I b PM 0.00 7.5 * 9.7 NL WI08 ORW1 UP O a AM 0.00 6.4 6.7 5.2 NL WI08 ORW1 UP O b AM 0.00 6.4 6.7 6.8 NL WI08 ORW1 UP O a PM 0.00 6.6 5.8 10.2 NL SP08 OWC PF O b PM 0.42 19.0 * 20.0 NL SP08 ORW1 UP I a AM 0.00 10.0 * 10.0 NL SP08 ORW1 UP I b AM 0.00 10.0 * 9.0 NL SP08 ORW1 UP I a PM 0.00 12.3 * 17.0 NL SP08 ORW1 UP I b PM 0.00 12.3 * 16.5 NL SP08 ORW1 UP O a AM 0.00 13.0 * 19.0 NL SP08 ORW1 UP O b AM 0.00 13.0 * 23.0 NL SP08 ORW1 UP O a PM 0.00 14.0 13.5 20.0 NL SU08 OWC PF O b PM 0.48 26.0 * 38.0 4 SU08 ORW1 UP I a AM 0.00 * * 25.5 NL SU08 ORW1 UP I b AM 0.00 * * 26.2 4 SU08 ORW1 UP I a PM 0.00 * * 25.0 NL SU08 ORW1 UP I b PM 0.00 * * 25.0 NL SU08 ORW1 UP O a AM 0.00 * * 21.0 4 SU08 ORW1 UP O b AM 0.00 * * 19.7 NL SU08 ORW1 UP O a PM 0.00 24.0 * 0.0 NL SU06 ORW2 UP O b PM 0.00 31.0 30.3 35.0 NL SU06 ORW2 IF I a AM 0.07 28.0 28.5 29.0 36 SU06 ORW2 IF I b AM 0.07 28.0 28.5 27.0 46 SU06 ORW2 IF I a PM 0.11 30.0 29.5 30.5 121 SU06 ORW2 IF I b PM 0.11 30.0 29.5 32.5 63 SU06 ORW2 IF O a AM 0.04 27.0 27.0 32.0 4 SU06 ORW2 IF O b AM 0.02 27.0 27.0 28.5 2 SU06 ORW2 IF O a PM 0.04 33.0 30.5 33.5 3 AU06 ORW2 UP O b PM 0.00 7.0 * 11.0 NL AU06 ORW2 IF I a AM 0.05 4.5 4.2 10.9 3 AU06 ORW2 IF I b AM 0.07 4.2 4.1 12.0 NL AU06 ORW2 IF I a PM 0.06 6.0 5.5 7.0 5 AU06 ORW2 IF I b PM 0.07 6.0 5.5 8.0 4 AU06 ORW2 IF O a AM 0.19 6.2 6.7 10.2 1 AU06 ORW2 IF O b AM 0.14 6.2 6.4 15.2 0 AU06 ORW2 IF O a PM 0.18 8.0 * 8.0 1 SU07 ORW2 UP O b PM 0.00 26.5 * 29.0 NL SU07 ORW2 IF I a AM 0.00 22.5 23.0 23.0 NL SU07 ORW2 IF I b AM 0.00 22.5 23.0 23.0 5 SU07 ORW2 IF I a PM 0.00 23.5 23.5 28.0 NL

Continued 170 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU07 ORW2 IF I b PM 0.00 23.5 23.5 28.0 NL SU07 ORW2 IF O a AM 0.03 23.5 23.0 21.0 4 SU07 ORW2 IF O b AM 0.03 23.5 23.0 21.0 4 SU07 ORW2 IF O a PM 0.03 29.5 32.0 29.0 4 AU07 ORW2 UP O b PM 0.00 6.0 * 11.0 NL AU07 ORW2 IF I a AM 0.09 4.0 5.0 1.0 2 AU07 ORW2 IF I b AM 0.09 3.8 4.3 1.0 NL AU07 ORW2 IF I a PM 0.10 2.0 * 9.0 16 AU07 ORW2 IF I b PM 0.09 2.0 * 9.0 NL AU07 ORW2 IF O a AM 0.18 2.5 * 0.5 NL AU07 ORW2 IF O b AM 0.20 2.5 * 2.5 NL AU07 ORW2 IF O a PM 0.20 7.0 * 9.0 1 WI08 ORW2 UP O b PM 0.00 7.0 7.4 12.5 NL WI08 ORW2 IF I a AM 0.16 3.0 * 5.0 17 WI08 ORW2 IF I b AM 0.12 3.0 * 6.0 1 WI08 ORW2 IF I a PM 0.15 1.0 1.0 11.2 13 WI08 ORW2 IF I b PM 0.17 1.0 1.0 10.6 0 WI08 ORW2 IF O a AM 0.30 4.0 * 6.0 NL WI08 ORW2 IF O b AM 0.28 3.0 * 7.0 3 WI08 ORW2 IF O a PM 0.34 4.5 5.0 11.0 2 SP08 ORW2 UP O b PM 0.00 19.0 18.0 19.0 1 SP08 ORW2 IF I a AM 0.00 11.3 12.0 15.2 NL SP08 ORW2 IF I b AM 0.00 11.3 12.0 17.0 NL SP08 ORW2 IF I a PM 0.00 15.1 14.0 22.0 1 SP08 ORW2 IF I b PM 0.00 15.0 14.0 20.0 NL SP08 ORW2 IF O a AM 0.00 16.0 14.0 19.5 NL SP08 ORW2 IF O b AM 0.00 16.0 14.0 19.5 NL SP08 ORW2 IF O a PM 0.00 17.0 16.0 23.0 NL SU08 ORW2 UP O b PM 0.00 24.0 * 28.0 NL SU08 ORW2 IF I a AM 0.08 20.0 * 16.0 NL SU08 ORW2 IF I b AM 0.08 20.0 * 17.0 NL SU08 ORW2 IF I a PM 0.07 22.0 * 22.0 2 SU08 ORW2 IF I b PM 0.07 22.0 * 22.0 1 SU08 ORW2 IF O a AM 0.14 22.0 * 21.0 -46 SU08 ORW2 IF O b AM 0.22 22.0 * 21.0 NL SU08 ORW2 IF O a PM 0.14 28.0 * 27.0 18 SU06 ORW2 IF O b PM 0.02 33.0 30.5 35.0 3 SU06 ORW2 PF I a AM 0.21 30.0 29.8 28.5 0 SU06 ORW2 PF I b AM 0.22 29.0 28.5 29.5 0 SU06 ORW2 PF I a PM 0.18 29.5 29.0 38.5 0 SU06 ORW2 PF I b PM 0.19 29.5 29.0 37.5 0 SU06 ORW2 PF O a AM 0.13 28.0 27.5 29.5 1 SU06 ORW2 PF O b AM 0.11 27.0 27.0 30.0 7 SU06 ORW2 PF O a PM 0.11 31.0 29.0 40.0 NL AU06 ORW2 IF O b PM 0.15 8.0 * 9.0 NL AU06 ORW2 PF I a AM 0.22 7.0 * 16.0 NL AU06 ORW2 PF I b AM 0.23 7.0 * 13.0 0 AU06 ORW2 PF I a PM 0.21 6.5 * 11.0 0 AU06 ORW2 PF I b PM 0.21 6.5 * 11.0 0 AU06 ORW2 PF O a AM 0.20 6.0 * 17.0 0

Continued 171 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) AU06 ORW2 PF O b AM 0.20 6.0 * 17.0 1 AU06 ORW2 PF O a PM 0.24 8.0 * 9.0 NL SU07 ORW2 IF O b PM 0.03 29.5 32.0 30.0 5 SU07 ORW2 PF I a AM 0.09 25.0 * 25.0 44 SU07 ORW2 PF I b AM 0.09 25.0 * 24.5 22 SU07 ORW2 PF I a PM 0.08 34.0 * 37.0 NL SU07 ORW2 PF I b PM 0.08 34.0 * 37.0 NL SU07 ORW2 PF O a AM 0.16 28.0 28.3 23.0 6 SU07 ORW2 PF O b AM 0.15 28.0 28.3 22.0 3 SU07 ORW2 PF O a PM 0.15 24.8 24.8 34.0 21 AU07 ORW2 IF O b PM 0.17 7.0 * 11.0 NL AU07 ORW2 PF I a AM 0.24 3.5 * 1.0 2 AU07 ORW2 PF I b AM 0.24 3.5 * 1.0 2 AU07 ORW2 PF I a PM 0.22 7.0 8.0 12.0 NL AU07 ORW2 PF I b PM 0.22 7.0 8.0 11.0 NL AU07 ORW2 PF O a AM 0.26 2.0 * 2.0 0 AU07 ORW2 PF O b AM 0.26 2.0 * 2.0 0 AU07 ORW2 PF O a PM 0.26 6.3 * 11.0 1 WI08 ORW2 IF O b PM 0.34 4.5 5.0 11.0 NL WI08 ORW2 PF I a AM 0.40 1.0 0.0 7.0 NL WI08 ORW2 PF I b AM 0.40 1.0 * 7.0 NL WI08 ORW2 PF I a PM 0.32 4.5 4.5 9.0 0 WI08 ORW2 PF I b PM 0.32 4.5 4.5 9.0 NL WI08 ORW2 PF O a AM 0.33 0.1 * 7.0 NL WI08 ORW2 PF O b AM 0.33 0.1 * 7.0 NL WI08 ORW2 PF O a PM 0.38 7.0 * 11.0 NL SP08 ORW2 IF O b PM 0.00 17.0 16.0 21.5 NL SP08 ORW2 PF I a AM 0.00 12.3 13.0 22.0 NL SP08 ORW2 PF I b AM 0.00 11.0 12.0 19.0 NL SP08 ORW2 PF I a PM 0.00 13.0 14.0 20.0 NL SP08 ORW2 PF I b PM 0.00 13.0 15.0 21.5 NL SP08 ORW2 PF O a AM 0.00 12.3 13.0 16.3 41 SP08 ORW2 PF O b AM 0.00 14.0 13.3 17.0 8 SP08 ORW2 PF O a PM 0.00 15.0 * 20.0 2 SU08 ORW2 IF O b PM 0.14 28.0 * 26.0 NL SU08 ORW2 PF I a AM 0.18 24.0 23.0 20.3 NL SU08 ORW2 PF I b AM 0.18 24.0 23.0 19.0 0 SU08 ORW2 PF I a PM 0.15 24.8 24.1 30.0 2 SU08 ORW2 PF I b PM 0.15 24.8 24.1 30.0 12 SU08 ORW2 PF O a AM 0.16 21.0 21.0 20.5 NL SU08 ORW2 PF O b AM 0.16 21.0 21.0 19.5 3 SU08 ORW2 PF O a PM 0.21 24.1 23.7 37.0 28 SU06 ORW1 PF O b PM 0.16 26.5 0.0 31.0 0 SU06 ORW2 UP I a AM 0.00 26.0 25.0 27.0 NL SU06 ORW2 UP I b AM 0.00 26.0 25.0 25.0 0 SU06 ORW2 UP I a PM 0.00 39.5 39.0 36.0 NL SU06 ORW2 UP I b PM 0.00 38.0 39.0 32.0 NL SU06 ORW2 UP O a AM 0.00 27.5 27.5 24.5 NL SU06 ORW2 UP O b AM 0.00 26.5 26.5 26.0 NL SU06 ORW2 UP O a PM 0.00 31.0 30.0 36.0 0

Continued 172 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) AU06 ORW1 PF O b PM 0.23 7.0 * 14.0 NL AU06 ORW2 UP I a AM 0.00 6.0 * 12.0 0 AU06 ORW2 UP I b AM 0.00 6.0 * 13.0 0 AU06 ORW2 UP I a PM 0.00 8.0 * 12.0 NL AU06 ORW2 UP I b PM 0.00 10.0 * 11.0 0 AU06 ORW2 UP O a AM 0.00 7.0 * 17.0 0 AU06 ORW2 UP O b AM 0.00 7.0 * 16.0 NL AU06 ORW2 UP O a PM 0.00 7.0 * 10.0 -1 SU07 ORW1 PF O b PM 0.14 26.5 26.0 36.5 NL SU07 ORW2 UP I a AM 0.00 21.0 * 21.0 NL SU07 ORW2 UP I b AM 0.00 21.0 * 21.5 NL SU07 ORW2 UP I a PM 0.00 24.0 * 28.0 NL SU07 ORW2 UP I b PM 0.00 24.0 * 28.0 NL SU07 ORW2 UP O a AM 0.00 22.0 * 22.0 NL SU07 ORW2 UP O b AM 0.00 22.0 * 22.0 NL SU07 ORW2 UP O a PM 0.00 39.0 * 27.0 NL AU07 ORW1 PF O b PM 0.40 5.5 * 11.0 NL AU07 ORW2 UP I a AM 0.00 4.0 * -3.5 NL AU07 ORW2 UP I b AM 0.00 3.8 * -2.5 0 AU07 ORW2 UP I a PM 0.00 6.0 * 12.3 0 AU07 ORW2 UP I b PM 0.00 5.3 * 11.5 NL AU07 ORW2 UP O a AM 0.00 2.0 * 0.0 0 AU07 ORW2 UP O b AM 0.00 3.0 * 1.0 NL AU07 ORW2 UP O a PM 0.00 8.5 * 11.0 NL WI08 ORW1 PF O b PM 0.46 7.0 * 11.0 0 WI08 ORW2 UP I a AM 0.00 6.8 7.0 7.1 NL WI08 ORW2 UP I b AM 0.00 6.5 6.8 6.0 NL WI08 ORW2 UP I a PM 0.00 7.2 6.9 13.1 NL WI08 ORW2 UP I b PM 0.00 7.2 7.0 13.3 NL WI08 ORW2 UP O a AM 0.00 7.0 6.1 7.1 NL WI08 ORW2 UP O b AM 0.00 6.0 6.0 6.2 NL WI08 ORW2 UP O a PM 0.00 8.2 8.5 13.0 NL SP08 ORW1 PF O b PM 0.00 16.0 14.5 18.5 2 SP08 ORW2 UP I a AM 0.00 9.0 * 10.5 -1 SP08 ORW2 UP I b AM 0.00 9.5 * 11.0 -1 SP08 ORW2 UP I a PM 0.00 15.0 * 18.5 NL SP08 ORW2 UP I b PM 0.00 14.0 * 17.0 -1 SP08 ORW2 UP O a AM 0.00 13.0 * 19.0 NL SP08 ORW2 UP O b AM 0.00 13.0 * 13.0 NL SP08 ORW2 UP O a PM 0.00 19.0 18.0 17.5 NL SU08 ORW1 PF O b PM 0.18 22.3 22.5 0.0 NL SU08 ORW2 UP I a AM 0.00 18.0 * 15.5 0 SU08 ORW2 UP I b AM 0.00 18.0 * 15.5 NL SU08 ORW2 UP I a PM 0.00 19.0 * 20.0 NL SU08 ORW2 UP I b PM 0.00 19.0 * 21.0 NL SU08 ORW2 UP O a AM 0.00 19.0 * 18.0 NL SU08 ORW2 UP O b AM 0.00 19.0 * 19.0 0 SU08 ORW2 UP O a PM 0.00 24.0 * 28.0 NL SU06 OWC UP O b PM 0.00 24.0 22.0 30.0 NL SU06 OWC IF I a AM 0.00 22.0 22.0 21.0 0

Continued 173 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 OWC IF I b AM 0.00 21.3 21.3 20.3 NL SU06 OWC IF I a PM 0.00 29.0 27.0 30.0 0 SU06 OWC IF I b PM 0.00 30.8 27.8 32.0 1 SU06 OWC IF O a AM 0.00 23.0 23.0 23.0 2 SU06 OWC IF O b AM 0.03 23.0 23.0 23.0 8 SU06 OWC IF O a PM 0.00 28.5 27.0 34.5 5 AU06 OWC UP O b PM 0.00 6.5 * 4.8 NL AU06 OWC IF I a AM 0.00 9.0 10.0 6.8 NL AU06 OWC IF I b AM 0.00 9.0 10.0 6.8 NL AU06 OWC IF I a PM 0.00 9.0 9.6 5.0 NL AU06 OWC IF I b PM 0.00 9.5 10.0 4.8 NL AU06 OWC IF O a AM 0.04 7.0 7.5 4.5 0 AU06 OWC IF O b AM 0.00 7.0 7.5 5.0 1 AU06 OWC IF O a PM 0.00 7.0 7.3 4.0 NL SU07 OWC UP O b PM 0.00 21.0 * 27.0 NL SU07 OWC IF I a AM 0.14 22.3 22.0 25.0 12 SU07 OWC IF I b AM 0.17 22.3 22.0 25.0 6 SU07 OWC IF I a PM 0.13 23.0 22.0 34.3 47 SU07 OWC IF I b PM 0.17 23.0 22.0 38.5 1 SU07 OWC IF O a AM 0.00 20.8 21.5 17.5 1 SU07 OWC IF O b AM 0.00 20.8 21.5 17.8 0 SU07 OWC IF O a PM 0.00 27.0 25.5 35.0 0 WI08 OWC UP O b PM 0.00 3.2 * 7.0 2 WI08 OWC IF I a AM 0.00 1.0 0.1 4.0 NL WI08 OWC IF I b AM 0.00 1.0 1.0 3.0 5 WI08 OWC IF I a PM 0.00 5.3 4.3 6.0 3 WI08 OWC IF I b PM 0.00 6.0 5.0 7.0 1 WI08 OWC IF O a AM 0.00 2.1 * 4.5 NL WI08 OWC IF O b AM 0.00 3.0 * 3.8 NL WI08 OWC IF O a PM 0.00 5.0 4.0 10.0 NL SP08 OWC UP O b PM 0.00 12.0 * 17.0 NL SP08 OWC IF I a AM 0.00 12.2 13.0 17.0 NL SP08 OWC IF I b AM 0.00 13.0 14.0 16.0 3 SP08 OWC IF I a PM 0.00 18.0 15.0 21.5 NL SP08 OWC IF I b PM 0.00 18.0 15.0 21.5 NL SP08 OWC IF O a AM 0.13 12.5 12.5 12.0 NL SP08 OWC IF O b AM 0.12 12.5 12.5 13.5 -1 SP08 OWC IF O a PM 0.12 15.0 14.0 21.0 0 SU08 OWC UP O b PM 0.00 22.0 * 27.0 NL SU08 OWC IF I a AM 0.00 19.0 19.0 25.0 NL SU08 OWC IF I b AM 0.00 18.6 18.3 23.8 NL SU08 OWC IF I a PM 0.00 23.0 20.4 38.0 0 SU08 OWC IF I b PM 0.00 24.0 21.0 35.5 1 SU08 OWC IF O a AM 0.00 18.8 19.0 19.5 189 SU08 OWC IF O b AM 0.00 19.0 19.0 21.0 NL SU08 OWC IF O a PM 0.00 21.0 19.8 28.2 NL SU06 OWC IF O b PM 0.00 29.0 27.0 29.0 NL SU06 OWC PF I a AM 0.16 22.3 22.3 22.0 4 SU06 OWC PF I b AM 0.23 23.0 23.0 22.3 NL SU06 OWC PF I a PM 0.15 28.0 27.0 36.0 4

Continued 174 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 OWC PF I b PM 0.19 28.8 27.0 38.0 6 SU06 OWC PF O a AM 0.27 25.5 25.5 25.0 2 SU06 OWC PF O b AM 0.24 26.0 26.0 29.0 9 SU06 OWC PF O a PM 0.27 32.0 32.0 35.0 5 AU06 OWC IF O b PM 0.00 7.0 7.3 4.5 NL AU06 OWC PF I a AM 0.15 9.5 * 9.0 43 AU06 OWC PF I b AM 0.33 9.5 * 10.5 11 AU06 OWC PF I a PM 0.25 9.0 9.0 9.5 1 AU06 OWC PF I b PM 0.33 9.0 9.0 9.0 1 AU06 OWC PF O a AM 0.28 7.0 * 7.0 NL AU06 OWC PF O b AM 0.31 7.0 * 6.0 2 AU06 OWC PF O a PM 0.19 6.5 8.0 8.0 1 SU07 OWC IF O b PM 0.00 25.0 22.5 34.8 2 SU07 OWC PF I a AM 0.50 25.5 * 29.5 85 SU07 OWC PF I b AM 0.50 26.8 * 27.0 36 SU07 OWC PF I a PM 0.52 31.5 * 36.0 36 SU07 OWC PF I b PM 0.54 29.2 * 35.0 23 SU07 OWC PF O a AM 0.38 24.3 * 26.8 1 SU07 OWC PF O b AM 0.44 24.3 * 27.5 18 SU07 OWC PF O a PM 0.43 27.0 * 40.0 12 WI08 OWC IF O b PM 0.00 5.0 4.0 9.8 NL WI08 OWC PF I a AM 0.13 2.0 * 5.0 NL WI08 OWC PF I b AM 0.25 2.5 * 5.0 NL WI08 OWC PF I a PM 0.34 3.5 * 10.0 4 WI08 OWC PF I b PM 0.25 3.5 * 10.0 2 WI08 OWC PF O a AM 0.04 1.0 * 4.0 NL WI08 OWC PF O b AM 0.04 1.0 * 4.0 10 WI08 OWC PF O a PM 0.11 1.0 * 10.0 6 SP08 OWC IF O b PM 0.12 15.0 14.0 22.5 0 SP08 OWC PF I a AM 0.51 13.0 * 13.5 NL SP08 OWC PF I b AM 0.58 15.0 * 14.0 1 SP08 OWC PF I a PM 0.41 19.5 * 24.0 1 SP08 OWC PF I b PM 0.39 19.0 * 22.0 1 SP08 OWC PF O a AM 0.45 14.5 * 15.0 23 SP08 OWC PF O b AM 0.45 14.5 * 17.0 NL SP08 OWC PF O a PM 0.42 19.0 * 30.0 1 SU08 OWC IF O b PM 0.00 21.0 20.0 27.5 36 SU08 OWC PF I a AM 0.26 23.0 * 28.0 NL SU08 OWC PF I b AM 0.21 23.9 * 29.0 2 SU08 OWC PF I a PM 0.27 27.5 * 38.0 NL SU08 OWC PF I b PM 0.24 27.2 * 33.0 NL SU08 OWC PF O a AM 0.53 23.0 * 18.5 33 SU08 OWC PF O b AM 0.48 22.5 * 18.0 NL SU08 OWC PF O a PM 0.46 26.0 * 38.8 1 SU06 LS PF O b PM 0.00 26.0 26.0 28.0 NL SU06 OWC UP I a AM 0.00 21.3 21.0 23.3 NL SU06 OWC UP I b AM 0.00 21.3 21.3 23.0 NL SU06 OWC UP I a PM 0.00 24.5 23.5 28.0 NL SU06 OWC UP I b PM 0.00 23.3 23.0 27.0 NL SU06 OWC UP O a AM 0.00 22.0 21.0 22.0 NL

Continued 175 Table D1 continued

H2O Level Soil 5cm Soil 10cm Air CH4-C (mg Period Wetland Location Site Rep Time (cm) (°C) (°C) (°C) m-2 hr-1) SU06 OWC UP O b AM 0.00 23.0 21.0 23.0 NL SU06 OWC UP O a PM 0.00 26.0 23.0 28.5 NL SU06 ORW2 PF O b PM 0.13 31.0 29.0 36.0 0 AU06 OWC UP I a AM 0.00 10.0 * 7.7 NL AU06 OWC UP I b AM 0.00 10.0 * 7.0 NL AU06 OWC UP I a PM 0.00 9.5 * 5.0 0 AU06 OWC UP I b PM 0.00 9.0 * 5.0 0 AU06 OWC UP O a AM 0.00 6.8 * 4.5 NL AU06 OWC UP O b AM 0.00 6.8 * 4.5 NL AU06 OWC UP O a PM 0.00 6.5 * 4.0 NL SP07 LS PF O b PM 0.00 25.0 24.5 27.0 NL SU07 OWC UP I a AM 0.00 20.5 * 21.8 NL SU07 OWC UP I b AM 0.00 21.0 * 21.5 NL SU07 OWC UP I a PM 0.00 22.5 * 29.0 0 SU07 OWC UP I b PM 0.00 22.0 * 29.0 0 SU07 OWC UP O a AM 0.00 20.0 * 22.3 NL SU07 OWC UP O b AM 0.00 19.5 * 23.0 NL SU07 OWC UP O a PM 0.00 21.2 * 26.8 NL AU07 ORW2 PF O b PM 0.26 6.3 * 12.5 1 WI08 OWC UP I a AM 0.00 2.0 * 4.0 NL WI08 OWC UP I b AM 0.00 2.0 * 4.5 NL WI08 OWC UP I a PM 0.00 2.5 * 7.5 NL WI08 OWC UP I b PM 0.00 2.5 * 7.0 -1 WI08 OWC UP O a AM 0.00 2.0 * 4.0 NL WI08 OWC UP O b AM 0.00 2.0 * 4.0 NL WI08 OWC UP O a PM 0.00 5.0 * 5.0 NL WI08 ORW2 PF O b PM 0.38 7.0 * 11.0 NL SP08 OWC UP I a AM 0.00 11.5 * 14.0 NL SP08 OWC UP I b AM 0.00 12.0 * 14.0 NL SP08 OWC UP I a PM 0.00 13.5 * 16.0 NL SP08 OWC UP I b PM 0.00 13.5 * 18.0 NL SP08 OWC UP O a AM 0.00 11.0 * 14.8 NL SP08 OWC UP O b AM 0.00 10.5 * 13.0 NL SP08 OWC UP O a PM 0.00 12.0 * 19.0 0 SU08 LS PF O b PM 0.10 24.8 25.0 25.3 2 SU08 OWC UP I a AM 0.00 20.0 * 23.2 NL SU08 OWC UP I b AM 0.00 20.0 * 23.0 NL SU08 OWC UP I a PM 0.00 22.8 * 27.0 NL SU08 OWC UP I b PM 0.00 23.0 * 27.0 NL SU08 OWC UP O a AM 0.00 18.8 * 20.1 -1 SU08 OWC UP O b AM 0.00 19.9 * 20.5 0 SU08 OWC UP O a PM 0.00 22.1 * 27.3 NL

176