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Marine lab, FGCU documenting effects of river runoff on estuary

By Staff | Jun 24, 2020

SCCF FGCU senior Kira Kreke measures light attenuation.

The Sanibel-Captiva Conservation Foundation’s Marine Lab is working with Florida Gulf Coast University scientists on an EPA grant designed to improve the understanding of how water management and poor-quality runoff affects seagrasses and contributes to algae blooms.

Freshwater inflows to the Caloosahatchee have changed in timing and quality as development has occurred, according to the SCCF. Instead of a steady flow of clean water filtered through swamps and the aquifer, rapid runoff events bring particles, pesticides and nutrients, and fast salinity changes. It has resulted in an unbalanced ecosystem with tape grass and seagrasses in poor shape, and not plentiful enough to feed manatees in much of the estuary.

“We’ve been noticing a lot of macroalgae, which happens when the water has been clear and there aren’t enough algae grazers such as snails and mullet,” lab research scientist Dr. Rick Bartleson said.

Dr. James Douglass and his students are sampling 100 shallow transects to document the location and condition of seagrasses in the estuary. Dr. Hidetoshi Urakawa and his students are monitoring the microbial community in the seagrass beds and the water column. Dr. Puspa Adhikari and his students are measuring the water chemistry in wells and measuring radium in the estuary to estimate submarine groundwater inflows.

The Marine Lab scientists are assisting in the efforts and will also install a continuous nutrient monitoring system in Fort Myers, along with measuring nutrients in grab samples from wells and the estuary, improving the light attenuation calculation, identifying algae and testing for herbicides.

SCCF Volunteer Jacob Lemmon assists the SCCF staff with planting tape grass.

The recent high salinities upriver have further reduced tape grass coverage. Information gathered will improve a seagrass ecosystem model that can be added to the weekly “Caloosatchee & Estuary Condition Report” and help guide water management decisions.