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 Salinity Light Dirt & Silt Tannins (CDOM) Water Movement Nutrients Epiphytic Algae Animal Interactions Phytoplankton Nutrients

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

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 – Environmental conditions fluctuate over time – Increases stress Time Conditions Past Present Low High

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

Temporal Variation in an Estuary Location in Estuary RANGE of Salinity River OceanMid Estuary 0 Salinity naturally fluctuates due to tides, rainfall, seasons, etc. 35 Middle part of estuary usually varies the most

Caloosahatchee River Estuary Mostly Salty Mixed and Variable Mostly Fresh

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

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

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 – 1m 2 quadrats (30) – SAV coverage, canopy height, etc. Historical data from SFWMD, back to 1998 Including salinity data 1 m 2

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 ( 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 Native grazers clean SAV and love salinity Water releases contain nutrients that stimulate phytoplankton in water and epiphytes on SAV

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