Zooplankton As Indicators of Lake Change in a Dredged Southwest Florida Lake
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Ecological Indicators of Restoration Success: Zooplankton as Indicators of Lake Change in a Dredged Southwest Florida Lake A Thesis Presented to The Faculty of the College of Arts and Sciences Florida Gulf Coast University In Partial Fulfillment Of the Requirements for the Degree of Master of Science in Environmental Science By John A Ferlita II May 2014 2 Florida Gulf Coast University Thesis APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Masters of Science ______________________________ John A Ferlita II Approved: May 2014 ______________________________ Edwin M. Everham, III, Ph.D. Committee Chair/Advisor ______________________________ David W. Ceilley, MS Co-Chair/Advisor ______________________________ Serge Thomas, Ph.D. Committee Member 3 ACKNOWLEDGEMENTS I would like to thank the Big Cypress Basin Board of the South Florida Water Management District for providing the funding to Florida Gulf Coast University which allowed me to conduct this research; FGCU’s Inland Ecology Research Group for providing me with a graduate research assistantship and all equipment, materials, and vehicles necessary; the College of Arts and Science and Coastal Watershed institute for the use of field vehicles; all the wonderful people of the Lake Trafford Marina; and of course my parents for encouraging me to pursue a Master’s degree. I would particularly like to express my appreciation to my committee members for being professors, mentors, employers, and friends throughout my time at FGCU; to my committee Chair Win Everham with FGCU for teaching me how to be a scientist, keeping me focused, and providing insurmountable knowledge and experience; to my co-chair and mentor David W. Ceilley for guidance, support, and teaching me all the knowledge and skills needed to complete my degree; and to committee member Serge Thomas providing extensive limnological knowledge and making me a better and more confident scientist and researcher. 4 ABSTRACT Eutrophication, caused by excess inputs of nutrients in lakes, rivers, estuaries, and coastal oceans, is a worldwide problem. Although the addition of nutrients may lead to abrupt increases in eutrophication, immediate decreases of such inputs do not always cause rapid or complete reversal of eutrophic conditions. Internal nutrient loading will often drive the eutrophication status of the lake and delay its recovery. Internal loading can often be vastly decreased by sediment removal through sediment dredging, which has been used in many lake restoration projects as an eco-engineering technology. However, it is still a controversial technique. Biological assessments are currently the chief method used to determine the integrity or “bio-integrity” of an ecosystem. Aquatic invertebrates are an integral part of freshwater biotic communities and can be used to indicate disturbance or recovery of aquatic systems. Zooplankton is a major contributor to the importance of invertebrates within aquatic systems. Zooplankton has potential value as indicators of changing trophic state since community structure and composition are greatly affected by disturbed conditions such as eutrophication. The objectives of this study were to: i) examine the spatial and temporal patterns of zooplankton in Lake Trafford, ii) explore possible controlling factors for changes in the zooplankton community (including water parameters and phytoplankton), and iii) evaluate the potential use of zooplankton community characteristics as a measure of lake health in a post dredged southwest Florida lake. Our findings indicate spatial distribution of zooplankton is highly variable within Lake Trafford and the influence of wind and wind driven waves seem to be the driving factors for this water body. Seasonal patterns of zooplankton abundance are opposite of the normal summer peaks and winter lows. In addition the seasonal peaks appear to be becoming less severe over 5 time thus, potentially indicating a more stable lake ecosystem subsequent to dredging. The stabilization and indication of the altered community structure is apparent and may be a precursor to major lake change. It appears that a transitional period is taking place and continued monitoring should ideally reveal a definitive lake change. Temperature was shown to be the most important abiotic factor driving zooplankton abundance. Zooplankton was indeed negatively correlated with temperature in Lake Trafford. Water temperature and conductance were key factors during the spring and summer seasons while other abiotic factors (DO, pH, light penetration, and wind) were more important in the winter and fall. A significant correlation between phytoplankton and zooplankton was found; however, their relationship is weak. Further study into alternative bottom-up control is suggested. Unique spatial and temporal patterns of zooplankton abundance exit in Lake Trafford. Continued monitoring of zooplankton may help illuminate post-dredging biotic dynamics and guide management decisions. A deeper understanding of Lake Trafford dynamics may help inform management decision on other eutrophic subtropical lakes. 6 TABLE OF CONTENTS Page Approval Sheet....………………………………………………………………………………... 2 Acknowledgments.………………………………………………………………………………. 3 Abstract.......……………………………………………………………………………………....4 Table of Contents…………..……………………………………………………………………. 6 List of Figures..…………………………………………………………………………………...7 List of Tables……………………………………………………………………………………...8 Introduction....………………………………………………………………………………….... 9 Objectives………………………………………………………………………………………..21 Methods…………………….…………………………………………………………………....23 Results……….……….....……….………………………………………………………………27 Discussion……………….……….……………………………………………………………....59 Summary Conclusions and Recommendations...…………………………….………………….69 Literature Cited....……………...………………………………………………………………..71 APPENDIX A: Surfer Maps of Zooplankton Distribution.....………........……………………..77 APPENDIX B: Zooplankton MDS and Zooplankton-phytoplankton MDS Ordinations...……..96 APPENDIX C: Results of SIMPER and ANOSIM Analysis..………………………………….97 APPENDIX D: Zooplankton Density and Temperature Bar Graph…………………………....100 APPENDIX E: Phytoplankton Bubble Overlays……………………………………………… 102 7 LIST OF FIGURES Page Figure 1. Map of Southwest Florida, location of Lake Trafford and sampling sites……….…..20 Figure 2a. Surfer map of zooplankton spatial variation, June 2010 ……………………………27 Figure 2b. Surfer map of zooplankton spatial variation, December 2010………………………28 Figure 3. Mean densities for major zooplankton groups …………………………………….....29 Figure 4. Cluster diagram of zooplankton sampling points grouped by year…………………..30 Figure 5. MDS ordination of the biweekly sampling zooplankton population data……………31 Figure 6. MDS ordination of zooplankton points by year and trajectory overlay………………32 Figure 7. 2D bubble overlay of Cladoceran zooplankton abundance for all data points……….33 Figure 8. 2D bubble overlay of Calanoid zooplankton abundance for all data points………….34 Figure 9. 2D bubble overlay of Cyclopoid zooplankton abundance for all data points………...35 Figure 10. 2D bubble overlay of Ostracod zooplankton abundance for all data points………..36 Figure 11. 2D bubble overlay of Rotifer zooplankton abundance for all data points.………….37 Figure 12. Principle Componant Analysis (PCA) of abiotic parameters……….……………….43 Figure 13. Principle Componant Analysis (PCA) of abiotic parameters. Overlayed is data points by year in mutlidimentional space………………...………………………44 Figure 14. Principle Componant Analysis (PCA) of abiotic parameters. Overlayed is data points by season in mutlidimentional space………………...……………………45 Figure 15. Correlation scatter plot of zooplanton mean abundance and temperature....………..46 Figure 16. Correlation scatter plot of zooplanton mean abundance and dissolved oxygen…….47 Figure 17. Correlation scatter plot of zooplanton mean abundance and secchi depth………….48 Figure 18. Correlation scatter plot of zooplanton mean abundance and conductance………….49 Figure 19. Correlation scatter plots of zooplankton and temperature for each sampling year….50 Figure 20. Mean densities for major zooplankton groups and temperature over time………….51 8 Figure 21. Cluster analysis of zooplankton-phytoplankton sampling points grouped by year…52 Figure 22. MDS ordination of the biweekly sampling zooplankton and phytoplankton data….53 Figure 23. MDS ordination of the biweekly sampling zooplankton and phytoplankton data with trajectory overlay....……..…………………………………………………………54 Figure 24. Mean total phytoplankton and total zooplankton biomass over time……………….55 Figure 25. Zooplankton biomass volume and phytoplankton mean totals as ratio over time…..56 Figure 26. Correlation scatter plot of zooplankton biomass (tot_biov) vs phytoplankton concentration (C_tot) (fall-winter data)…….…………………………………………..57 Figure 27. Correlation scatter plot of zooplankton biomass (tot_biov) vs phytoplankton Concentration (C_tot) (spring-summer data)……………..…………………………….58 LIST OF TABLES Table 1. SIMPER results of zooplankton group comparison for 2010 and 2011……………….38 Table 2. SIMPER results of zooplankton group comparison for 2010 and 2012……………….39 Table 3. SIMPER results of zooplankton group comparison for 2010 and 2013……………….39 Table 4. SIMPER results of zooplankton group comparison for 2011 and 2012……………….40 Table 5. SIMPER results of zooplankton group comparison for 2011 and 2013……………….40 Table 6. SIMPER results of zooplankton group comparison for 2012 and 2013……………….41 Table 7. ANOSIM results for study year comparison