Transcript Slide 1
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 • Saltwater SAV is called seagrass SAV has real roots and leaves, unlike seaweed • SAV – Affected by many aspects of the environment – Indicator of Environmental Health Temperature Light Phytoplankton Tannins (CDOM) Dirt & Silt Salinity Epiphytic Algae Water Movement • SAV – Different species need different levels of salinity to survive. Salinity Common Caloosahatchee SAV • Turtlegrass: – Thalassia testudinium – 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 2 Types of Environmental Variation 1. Spatial variation – Environmental conditions vary from place to place – Increases species diversity 2. Temporal variation Conditions – Environmental conditions fluctuate over time – Increases stress High Low Past Time Present Spatial Variation in an Estuary • Salinity blends from fresh to salty along the estuary AVERAGE Freshwater Salinity Species 35 Marine Species Live Here Live Here 0 River Mid Estuary Location in Estuary Ocean Temporal Variation in an Estuary • Salinity naturally fluctuates due to tides, rainfall, seasons, etc. 35 RANGE of Salinity Middle part of estuary usually varies the most River Mid Estuary Location in Estuary Ocean 0 Caloosahatchee River Estuary Mostly Fresh Mixed and Variable Mostly Salty 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 • Damming and Dumping fresh water increase variability in estuary 35 Increased variability due to human interference RANGE of Salinity Increased stress for SAV River Mid Estuary Location in Estuary Ocean 0 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 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 Methods • 7 sites along estuary • Bimonthly monitoring – 1m2 quadrats (30) – SAV coverage, canopy height, etc. • Historical data from SFWMD, back to 1998 • Including salinity data 1 2 m Results: 1998 – 2013 Freshwater Flow • Often, too much or too little water was released Results: 1999 – 2013 Salinity • Temporal variability of salinity was extreme Analysis: Linking Salinity to S-79 Flow • Strong Links: – Less Flow = More Salinity – More Flow = Less Salinity Linking SAV to Salinity; Upper Estuary • Vallisneria died off whenever salinity got > 10 psu • Recovery takes years • Down for the count? Linking SAV to Salinity; Middle Estuary • Halodule wrightii very scarce during low salinity • Recovery during higher salinity, but still struggling 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 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 Water releases contain nutrients that stimulate phytoplankton in water and epiphytes on SAV Native grazers clean SAV and love salinity Acknowledgements • Elizabeth Orlando, Peter Doering and other SFWMD Staff • Dr. Aswani Volety, 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