Effects of Altered Freshwater Flow James G Douglass FGCU Seagrass Scientist Estuary A semienclosed body of water where freshwater mixes with seawater Salinity SAV Submersed Aquatic Vegetation ID: 424078
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Slide1
SAV
in the Caloosahatchee Estuary;Effects of Altered Freshwater Flow
James G. DouglassFGCU Seagrass ScientistSlide2
Estuary
A semi-enclosed body of water where freshwater mixes with seawater
SalinitySlide3
SAV = Submersed Aquatic Vegetation
True Plants that live entirely underwaterSaltwater
SAV is called seagrass
SAV
has real roots and leaves, unlike
seaweedSlide4
SAV
Affected by many aspects of the environmentIndicator of Environmental Health
Temperature
Salinity
Light
Dirt & Silt
Tannins (CDOM)
Water Movement
Nutrients
Epiphytic Algae
Animal Interactions
Phytoplankton
NutrientsSlide5
Salinity
SAV
Different species need different levels of salinity to survive.Slide6
Common Caloosahatchee SAV
Turtlegrass: Thalassia
testudiniumPrefers full salinity of oceanTolerates ~2/3 ocean salinity
Shoalgrass: Halodule wrightii
Prefers full salinity of oceanTolerates ~1/2 ocean salinityTapegrass:Vallisneria americanaPrefers freshwaterTolerates ~1/4 ocean salinitySlide7
2 Types of Environmental Variation
Spatial variation Environmental conditions vary from place to placeIncreases
species diversityTemporal variation
Environmental conditions fluctuate over timeIncreases stress
Time
Conditions
Past
Present
Low
HighSlide8
Marine Species Live Here
Freshwater Species Live Here
Spatial
Variation in an Estuary
Location in Estuary
AVERAGE
Salinity
0
35
River
Ocean
Mid Estuary
Salinity blends from fresh to salty along the estuarySlide9
Temporal Variation
in an EstuaryLocation 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 mostSlide10
Caloosahatchee River Estuary
Mostly Salty
Mixed and Variable
Mostly FreshSlide11
S-79 Dam Controls Flow to Estuary
SFWMD Scientists have determined that:
Upper estuary gets
too salty when flow is < 450 cfsLower estuary gets
too fresh when flow is > 2800 cfsAlso, pollution problems during high flowSlide12
Location in Estuary
RANGE
of Salinity
River
Ocean
Mid Estuary
0
Damming
and
Dumping
fresh water
increase variability
in estuary
35
Increased variability due to human interference
Increased stress for SAVSlide13
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 damSlide14
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 conditionsTrack
SAV recovery as CERP is implementedSlide15
Methods
7 sites along estuary
Bimonthly monitoring1m2 quadrats
(30)SAV coverage, canopy height, etc.Historical data from SFWMD, back to 1998
Including salinity data
1 m
2Slide16
Results: 1998 – 2013 Freshwater Flow
Often, too much or too little water was releasedSlide17
Results: 1999 – 2013 Salinity
Temporal variability of salinity was extremeSlide18
Analysis: Linking Salinity to S-79 Flow
Strong Links: Less Flow = More SalinityMore Flow = Less SalinitySlide19
Linking SAV
to Salinity; Upper EstuaryVallisneria
died off whenever salinity got > 10 psuRecovery takes years
Down for the count?Slide20
Linking SAV
to Salinity; Middle EstuaryHalodule wrightii very scarce during low salinity
Recovery during higher salinity, but still strugglingSlide21
Conclusions
Diversity of SAV species with different salinity tolerances should allow
SAV along entire Estuary
But temporal variability of salinity is too highAdhering to flow envelope (450-2800 cfs) would helpSlide22
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 SAVSlide23
Acknowledgements
Elizabeth Orlando, Peter Doering and other SFWMD StaffDr. Aswani Volety, FGCULesli
Haynes, Christal Niemeyer, Tim BryantSylvie Mariolan, Heather Butler, Whitney McDowell, Spencer
Talmage, Romina Robles, Amber Chaboudy, and many other FGCU undergraduate students