Causes and Monitoring of Hypoxia in Corpus Christi Bay Publication CBBEP – 59 Project Number – 0817 May 2009 Final Report by Kevin Nelson, Ph.D. Candidate and Paul A. Montagna, Ph.D. Harte Research Institute for Gulf of Mexico Studies Texas A&M University – Corpus Christi Submitted to: Coastal Bend Bays & Estuaries Program 1305 N. Shoreline Blvd., Suite 205 Corpus Christi, TX 78401 The views expressed herein are those of the authors and do not necessarily reflect the views of CBBEP or other organizations that may have provided funding for this project. Causes and Monitoring of Hypoxia in Corpus Christi Bay Final Report By: Kevin Nelson, Ph.D. Candidate Paul A. Montagna, Ph.D. Harte Research Institute for Gulf of Mexico Studies Texas A&M University-Corpus Christi 6300 Ocean Drive, Unit 5869 Corpus Christi, TX 78412 361-825-2040 Telephone 361-825-2050 Facsimile Submitted To: Coastal Bend Bays & Estuaries Program 1305 N. Shoreline Blvd., Suite 205 Corpus Christi, TX 78401 CBBEP Project Number: 2008-17 May 12, 2009 Table of Contents List of Tables ............................................................................................................................................... 1 List of Figures .............................................................................................................................................. 2 Abstract ........................................................................................................................................................ 4 Introduction ................................................................................................................................................. 5 Methods ........................................................................................................................................................ 6 Study Location .......................................................................................................................................... 6 Equipment ................................................................................................................................................. 7 Nutrient Samples ....................................................................................................................................... 7 Chlorophyll-a ............................................................................................................................................ 7 Spatial and Temporal Extent ..................................................................................................................... 7 Results .......................................................................................................................................................... 8 Temporal Extent ........................................................................................................................................ 8 Spatial Extent ............................................................................................................................................ 8 Nutrient and Chlorophyll-a Concentrations .............................................................................................. 8 Hydrographic Parameters ........................................................................................................................ 10 Continuous Measurements ...................................................................................................................... 11 Nutrient Distributions ............................................................................................................................. 12 Discussion .................................................................................................................................................. 15 Temporal Extent ...................................................................................................................................... 15 Spatial Extent .......................................................................................................................................... 15 Possible Indications of Groundwater Flow ............................................................................................. 18 Summary .................................................................................................................................................... 18 References .................................................................................................................................................. 19 Appendix A. ............................................................................................................................................... 20 Nutrient Concentrations .......................................................................................................................... 20 Appendix B ................................................................................................................................................ 36 Hydrographic Measurements .................................................................................................................. 36 Appendix C ................................................................................................................................................ 46 Hypoxic Events ....................................................................................................................................... 46 Station 17787 ...................................................................................................................................... 46 Station 17793 ...................................................................................................................................... 47 Station 18247 ...................................................................................................................................... 48 Appendix D ................................................................................................................................................ 49 Continuous Measurements ...................................................................................................................... 49 Appendix E ................................................................................................................................................ 88 Study Station Coordinates ....................................................................................................................... 88 List of Tables Table 1. Mean chlorophyll (μ g/L) and nutrient (μM) concentrations by station.. ...................................... 9 Table 2. Mean hydrologic grab values by station. ..................................................................................... 10 Table 3. Mean hydrographic values for continuous sonde deployments. ................................................. 11 Table 4. Summary of hypoxia events. ........................................................................................................ 12 Table 5. Earliest Hypoxic Observation by Year. ....................................................................................... 15 Table 6. Latest Hypoxic Observation by Year. .......................................................................................... 15 Table 7. Observed Low-salinity Spikes ..................................................................................................... 18 1 List of Figures Figure 1. Map of 2008 Study Area .............................................................................................................. 6 Figure 2. YSI Sonde Deployment ................................................................................................................ 7 Figure 3. Interpolation of mean bottom ammonium concentrations ........................................................... 13 Figure 4. Interpolation of mean bottom orthophosphate concentrations .................................................... 14 Figure 5. Known spatial extent of hypoxic zone. ....................................................................................... 16 Figure 6. Interpolation of mean bottom dissolved oxygen concentrations ................................................. 17 Figure D. 1 Continuous surface monitoring at station 17781 during 5/19/08 - 5/27/08 deployment. ........ 49 Figure D. 2 Continuous bottom monitoring at station 17781 during 5/19/08 - 5/27/08 deployment. ........ 50 Figure D. 3 Continuous bottom monitoring at station 17787 during 5/19/08 - 5/27/08 deployment. ........ 51 Figure D. 4 Continuous surface monitoring at station 17793 during 5/19/08 - 5/27/08 deployment. ........ 52 Figure D. 5 Continuous bottom monitoring at station 17793 during 5/19/08 - 5/27/08 deployment. ........ 53 Figure D. 6 Continuous surface monitoring at station 18247 during 5/19/08 - 5/27/08 deployment. ........ 54 Figure D. 7 Continuous bottom monitoring at station 18247 during 5/19/08 - 5/27/08 deployment. ........ 55 Figure D. 8 Continuous surface monitoring at station 17781 during 6/18/08 - 6/25/08 deployment ......... 56 Figure D. 9 Continuous bottom monitoring at station 17781 during 6/18/08 - 6/25/08 deployment. ........ 57 Figure D. 10 Continuous surface monitoring at station 17787 during 6/18/08 - 6/25/08 deployment. ...... 58 Figure D. 11 Continuous bottom monitoring at station 17787 during 6/18/08 - 6/25/08 deployment. ...... 59 Figure D. 12 Continuous