Seagrass Response to Wastewater Inputs: Implementation of a Seagrass Monitoring Program in Two Texas Estuaries Cindy Contreras, Adam Whisenant, Jennifer M. Bronson, and Patricia L. Radloff Water Resources Branch Texas Parks and Wildlife Department 4200 Smith School Road Austin, Texas 78744 April 2011 Water Quality Technical Series WQTS-2011-02 Final Report Seagrass Response to Wastewater Inputs: Implementation of a Seagrass Monitoring Program in Two Texas Estuaries March 24, 2011 Cindy Contreras, Adam Whisenant, Jennifer M. Bronson, and Patricia L. Radloff Water Resources Branch Texas Parks and Wildlife Department 4200 Smith School Road Austin, Texas 78744-3291 GLO contract number: 10-049-000-3745 TPWD contract number: 211946 This work is funded in part by a grant/cooperative agreement from the National Oceanic and Atmospheric Administration. The views expressed herein are those of the author(s) and no not necessarily reflect the views of NOAA or any of its sub-agencies. Table of Contents Tables .............................................................................................................................................. 6 Appendix C ................................................................................................................................. 6 Appendix D ................................................................................................................................. 7 Appendix E ................................................................................................................................. 7 Appendix F.................................................................................................................................. 8 Figures............................................................................................................................................. 9 Appendix C ............................................................................................................................... 10 Appendix E ............................................................................................................................... 10 Appendix F................................................................................................................................ 11 Acronyms ...................................................................................................................................... 13 Acknowledgements ....................................................................................................................... 15 Executive Summary ...................................................................................................................... 17 Introduction ................................................................................................................................... 20 Study Area .................................................................................................................................... 21 Methods......................................................................................................................................... 26 Seagrass Basics ......................................................................................................................... 26 Aerial Imagery .......................................................................................................................... 26 Acquisition ............................................................................................................................ 26 Analysis................................................................................................................................. 27 Field Data Collection ................................................................................................................ 27 General Overview ................................................................................................................. 27 Instantaneous Physicochemical Measurements .................................................................... 30 Long-term Water Quality Measurements ............................................................................. 30 Water Chemistry ................................................................................................................... 30 Sediment Chemistry .............................................................................................................. 30 Quality Control for Water and Sediment Samples ............................................................... 31 Methods Comparison for Water and Sediment Samples ...................................................... 31 Macroalgae Collection .......................................................................................................... 31 Percent Vegetative Cover ..................................................................................................... 32 Seagrass Cores ...................................................................................................................... 33 Seagrass Shoot Collection..................................................................................................... 34 Processing and Analysis of Biological Samples ....................................................................... 36 Macroalgae ............................................................................................................................ 36 Seagrass Cores ...................................................................................................................... 36 Seagrass Shoots for Epiphyte Load ...................................................................................... 37 Data Analysis ............................................................................................................................ 37 Results ........................................................................................................................................... 37 Aerial Imagery .......................................................................................................................... 37 East Flats 2009 ...................................................................................................................... 37 Port Bay 2009 ....................................................................................................................... 41 East Flats 2010 ...................................................................................................................... 45 Port Bay 2010 ....................................................................................................................... 47 Site Characterization ................................................................................................................. 50 Instantaneous Physicochemical Measurements .................................................................... 50 3 Measures of Water Clarity .................................................................................................... 50 Long-Term Physicochemical Measurements ........................................................................ 52 Water Chemistry ................................................................................................................... 55 Sediment Characteristics ....................................................................................................... 55 Inter-laboratory Comparisons ................................................................................................... 58 Biological Parameters ............................................................................................................... 59 Seagrass Percent Coverage ................................................................................................... 59 Macroalgae Biomass ............................................................................................................. 62 Seagrass Shoot Density and Biomass ................................................................................... 62 Seagrass Leaf Area Index ..................................................................................................... 69 Epiphyte Loading .................................................................................................................. 69 Seagrass Stable Isotope ......................................................................................................... 82 Videography .......................................................................................................................... 85 Discussion ..................................................................................................................................... 86 Wastewater Impact .................................................................................................................... 87 Statewide Seagrass Monitoring ................................................................................................. 89 Aerial Imagery .......................................................................................................................... 92 Method .................................................................................................................................. 92 Comparison of 2009 and 2010 Imagery Analysis................................................................. 93 Conclusions ..................................................................................................................................