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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

SAV in the Caloosahatchee Estuary;Effects of Altered Freshwater Flow

James G. Douglass

FGCU Seagrass Scientist

estuary
Estuary
  • A semi-enclosed body of water where freshwater mixes with seawater

Salinity

sav submersed aquatic vegetation
SAV = Submersed Aquatic Vegetation
  • True Plants that live entirely underwater
  • SaltwaterSAV is called seagrass

SAV has real roots and leaves, unlike seaweed

slide4

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

slide5

SAV

    • Different species need different levels of salinity to survive.

Salinity

common caloosahatchee sav
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
2 types of environmental variation
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

spatial variation in an estuary
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

temporal variation in an estuary
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

caloosahatchee river estuary
Caloosahatchee River Estuary

Mostly Fresh

Mixed and Variable

Mostly Salty

s 79 dam controls flow to estuary
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
slide12

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

south fl water management district and the comprehensive everglades restoration plan
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
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
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

results 1998 2013 freshwater flow
Results: 1998 – 2013 Freshwater Flow
  • Often, too much or too little water was released
results 1999 2013 salinity
Results: 1999 – 2013 Salinity
  • Temporal variability of salinity was extreme
analysis linking salinity to s 79 flow
Analysis: Linking Salinity to S-79 Flow
  • Strong Links:
    • Less Flow = More Salinity
    • More Flow = Less Salinity
linking sav to salinity upper estuary
Linking SAVto Salinity; Upper Estuary
  • Vallisneriadied off whenever salinity got > 10 psu
  • Recovery takes years
  • Down for the count?
linking sav to salinity middle estuary
Linking SAV to Salinity; Middle Estuary
  • Halodule wrightii very scarce during low salinity
  • Recovery during higher salinity, but still struggling
conclusions
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
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
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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