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SAV in the Caloosahatchee Estuary; Effects of Altered Freshwater Flow

SAV in the Caloosahatchee Estuary; Effects of Altered Freshwater Flow. James G. Douglass FGCU Seagrass Scientist. Estuary. A semi-enclosed body of water where freshwater mixes with seawater. Salinity. SAV = Submersed Aquatic Vegetation. True Plants that live entirely underwater

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SAV in the Caloosahatchee Estuary; Effects of Altered Freshwater Flow

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  1. SAV in the Caloosahatchee Estuary;Effects of Altered Freshwater Flow James G. Douglass FGCU Seagrass Scientist

  2. Estuary • A semi-enclosed body of water where freshwater mixes with seawater Salinity

  3. SAV = Submersed Aquatic Vegetation • True Plants that live entirely underwater • SaltwaterSAV is called seagrass SAV has real roots and leaves, unlike seaweed

  4. Light Nutrients • SAV • Affected by many aspects of the environment • Indicator of Environmental Health Phytoplankton Tannins (CDOM) Animal Interactions Temperature Dirt & Silt Nutrients Salinity Epiphytic Algae Water Movement

  5. SAV • Different species need different levels of salinity to survive. Salinity

  6. Common Caloosahatchee SAV • Turtlegrass: • Thalassiatestudinium • Prefers full salinity of ocean • Tolerates ~2/3 ocean salinity • Shoalgrass: • Halodule wrightii • Prefers full salinity of ocean • Tolerates ~1/2 ocean salinity • Tapegrass: • Vallisneria americana • Prefers freshwater • Tolerates ~1/4 ocean salinity

  7. 2 Types of Environmental Variation • Spatial variation • Environmental conditions vary from place to place • Increases species diversity • Temporal variation • Environmental conditions fluctuate over time • Increases stress High Conditions Low Past Present Time

  8. Spatial Variation in an Estuary • Salinity blends from fresh to salty along the estuary 35 AVERAGE Salinity Freshwater Species Live Here Marine Species Live Here 0 River Mid Estuary Ocean Location in Estuary

  9. TemporalVariation in an Estuary • Salinity naturally fluctuates due to tides, rainfall, seasons, etc. 35 RANGE of Salinity Middle part of estuary usually varies the most 0 River Mid Estuary Ocean Location in Estuary

  10. Caloosahatchee River Estuary Mostly Fresh Mixed and Variable Mostly Salty

  11. S-79 Dam Controls Flow to Estuary • SFWMD Scientists have determined that: • Upper estuary gets too salty when flow is < 450 cfs • Lower estuary gets too fresh when flow is > 2800 cfs • Also, pollution problems during high flow

  12. Damming and Dumping fresh water increase variability in estuary 35 Increased variability due to human interference Increased stress for SAV RANGE of Salinity 0 River Mid Estuary Ocean Location in Estuary

  13. South FL Water Management District and the Comprehensive Everglades Restoration Plan CERP Projects should decrease the temporal variability of salinity in the Caloosahatchee Estuary by allowing a more steady amount of freshwater to be released through the S-79 lock and dam

  14. SAV Monitoring Objectives for the Caloosahatchee River Estuary • Determine SAV trends and variability from 1998 to the present • Relate SAV status and trends to environmental conditions • Track SAV recovery as CERP is implemented

  15. Methods • 7 sites along estuary • Bimonthly monitoring • 1m2quadrats (30) • SAV coverage, canopy height, etc. • Historical data from SFWMD, back to 1998 • Including salinity data 1 m2

  16. Results: 1998 – 2013 Freshwater Flow • Often, too much or too little water was released

  17. Results: 1999 – 2013 Salinity • Temporal variability of salinity was extreme

  18. Analysis: Linking Salinity to S-79 Flow • Strong Links: • Less Flow = More Salinity • More Flow = Less Salinity

  19. Linking SAVto Salinity; Upper Estuary • Vallisneriadied off whenever salinity got > 10 psu • Recovery takes years • Down for the count?

  20. Linking SAV to Salinity; Middle Estuary • Halodule wrightii very scarce during low salinity • Recovery during higher salinity, but still struggling

  21. Conclusions • Diversity of SAV species with different salinity tolerances should allow SAV along entire Estuary • But temporal variability of salinity is too high • Adhering to flow envelope (450-2800 cfs) would help

  22. Issues for Future Research • Interactive effects of freshwater releases, nutrients, and grazing organisms could exacerbate salinity stresses Invasive freshwater snail eats SAV, but hates salinity Native grazers clean SAV and love salinity Water releases contain nutrients that stimulate phytoplankton in water and epiphytes on SAV

  23. Acknowledgements • Elizabeth Orlando, Peter Doering and other SFWMD Staff • Dr. AswaniVolety, FGCU • Lesli Haynes, Christal Niemeyer, Tim Bryant • Sylvie Mariolan, Heather Butler, Whitney McDowell, Spencer Talmage, Romina Robles, Amber Chaboudy, and many other FGCU undergraduate students

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