The role of salt marsh as a net sink or source of carbon dioxide in Southwestern Gulf of Mexico Sang Rul Park, Joseph Stachelek, Kenneth Dunton School of Marine Biomedical Sciences, Jeju National University (2012-10-19 PICES) 2 Salt marsh ? • Transition zones between the ocean and the land # Functions and values - High primary productivity - Variable habitat high biodiversity - Nutrients recycling and filtration - Wave and current energy damping Thus, one of the most valuable ecosystems (Costanza et al. 1997) Carbon sequestration in Salt marsh Area Average rate Component Million km2 Ton C ha-1 y-1 Mangroves 0.17 1.39 Salt Marsh 0.40 1.51 Seagrass 0.33 0.83 *C = Organic carbon (Nellemann et al. 2009) Salt marshes decline (Nellemann et al. 2009) - Disappeared about 50% of marsh systems in U.S. (Kennish 2001) 5 Nueces River Delta - A part of the Nueces estuary system in Southwestern Gulf of Mexico (5700 ha) Nueces River Delta - Borrichia frutescens (Bf), Batis maritima (Bm), and Salicornia virginica (Sv) - 50% of vegetation cover - Since 1940, reduced freshwater input (over 99%) - Hypersalinity and water stress - Since 1940s, decline of 30-40% of net aerial primary production (Ward 1987, Solis 1994) - But, little photosynthetic research Objectives Quantify the seasonal 451 photosynthetic characteristics of marsh plants Photosynthetic responses to environmental stresses under natural conditions Construct a carbon budget for the Nueces River Delta Hypothesis The role of salt marsh as a net sink or source of CO2 depends on season Study sites 467 463 451 450 270 Google earth Experimental design - 25-m transect line Sv, Bf, Bm, Ml - All stations were Bf classified by vegetation Sv assemblages Bf - Station 451 (4 zones) - Two dominant Borrichia furtescens zones, - One dominant Salicornia virginica zone and - One mixed zone (Borrichia frutescens, Salicornia virginica, Batis maritima, Monanthochloe littoralis) 10 Data collection # Photosynthesis and respiration - Using LI-6400 portable gas exchange system with conifer chamber - Between 10:00 and 15:00 - For respiration, the chamber was shaded by a black plastic bag # Soil respiration - Using LI-6400 portable gas exchange system with soil chamber at bare bed and inside canopy # Environmental factors - Salinity, temperature and precipitation A 40 Average temp. Environmental Maximum temp. C) o factors 30 20 # Temperature 10 - Seasonal trend ( temperature Air 0 # Precipitation JJASONDJFMAMJ 400 400 B Precipitation - Very low Evapotranspiration 300 300 # Evapotranspiration 200 200 - highest during summer - lowest during fall-winter 100 100 Precipitation (mm) Evapotranspiration(mm) 0 0 JJASONDJFMAMJ 2010 2011 Salinity, moisture and nutrients Parameters Values Salinity (PSU) Tidal creek 4 – 35 Porewater 14 – 68 Soil moisture (%) 20 – 55 * Range Photosynthetic characteristics Station 467 Station 463 Station 451 Station 450 Station 270 16 ) -1 A B C D E Bf s -2 12 Sv m 2 Bm 8 molCO (µ 4 area A 0 ) F -1 G H I J s 6 -2 m 2 4 molCO (µ 2 area R 0 K L M N O 10 11.9 8 ratio 6 A:R 4 2 0 Su/10 F/10 W/11 Sp/11 Su/10 F/10 W/11 Sp/11 Su/10 F/10 W/11 Sp/11 Su/10 F/10 W/11 Sp/11 Su/10 F/10 W/11 Sp/11 *Aarea – net photosynthesis; Rarea – Respiration; Bf – B. frutescens; Sv – S. virginica; Bm – B. maritima. 25 10 2 2 Relationships between B. frutescens r = 0.25 *** B. frutescens r = 0.34 *** temperature and A, R 20 8 15 6 10 4 # Net photosynthesis 5 2 0 0 ) o ) -1 2 2 -1 - Bf (28 – 35 C) 10 S. virginica r = 0.06 ** S. virginica r = 0.30 *** s 8 s -2 -2 o 8 m C) m - Bm (31 – 37 2 6 2 6 4 4 mol CO mol CO µ µ 2 ( 2 ( area # Respiration area A 0 0 R 2 2 10 B. maritima r = 0.24 *** B. maritima r = 0.38 *** 5 - positive relationships 8 4 6 3 4 2 2 1 0 0 10 20 30 40 50 10 20 30 40 50 Leaf temperature (oC) Leaf temperature (oC) Relationships between 20 8 A 2 D porewater salinity and A, R r = 0.12 * 15 6 10 4 5 2 ) ) -1 # Borrichia frutescens -1 0 0 s B E s -2 10 8 -2 - Negative relationship m m 2 8 2 6 6 4 # Batis maritima 4 molCO 2 molCO µ 2 µ ( ( - positive relationship 0 0 area area C r2 = 0.19* F A 8 4 R 6 3 4 2 2 1 0 0 10 20 30 40 50 60 70 80 90 10 20 30 40 50 60 70 80 90 Porewater salinity Porewater salinity 16 Soil respiration 8 ) Inside canopy -1 Bare bed s -2 6 m 2 4 mol CO mol (µ 2 Effluex 0 Summer 2010 Fall 2010 Winter 2011 Spring 2011 Station 270 Carbon budget (calculation) - Vegetation coverage data (P, 2007-2008) and biomass (B, 2010) - Net photosynthesis (nmol g-1 DW s-1, 10 h) and respiration (14 hour), - Soil respiration (μmol CO2 m-2 s-1, 24 hour) - Biomass per unit area (BU, g DW) = P (%) X P/B ratio (g DW / %) Net Mol CO Area Mol CO BU 2 Res BU 2 Summer Photo m-2 d-1 (%) m-2 d-1 Batis maritima 69.4 43.3 0.108 19.9 43.3 0.043 B. frutescens 54.5 1222.8 2.399 26.5 1222.8 1.633 S. virginica 55.9 64.1 0.129 43.3 64.1 0.140 Soil respiration - - - 0.89 9.1 0.007 at bare bed Soil respiration - - - 5.78 64.3 0.321 inside canopy Total 2.636 2.145 Station 270 Carbon budget 3 ) -1 Carbon sink d -2 2 1 Exchange (mol m 2 0 Net CO Net Carbon source -1 Summer Fall Winter Spring Conclusions • Photosynthesis and respiration of plants - biomodal patterns and/or seasonal variations • High temperature - inhibit or accelerate net photosynthesis or respiration • Porewater salinity - Limitating factor of photosynthesis (B. frutescens) • The role of salt marsh depends on season - Carbon sink (spring-fall) and carbon source (winter) 20 Further study • Salt marsh network - North America and South Korea • Blue carbon mapping in Korea - including seaweed and seagrasses Acknowledgment - Kim Jackson - Travis Bartholomew - Kelly Darnell - Dana Sjostrom - Yun Hee Kang Questions? .