Coast News

New Tool Will Assess Water Discharge Impacts from Florida’s Everglades

The ongoing Comprehensive Everglades Restoration Plan (CERP) is working to restore the historical flow of the Florida Everglades to bring back the health of the ecosystem, which has seen declines in water quality and habitat loss and degradation.

The Southwest Florida coast, the Florida Keys Reef Tract and Florida Bay together support abundant underwater vegetation, corals and fishes as well as a prosperous tourist economy. At the epicenter of this region is the Florida Bay ecosystem, which is directly impacted by these watershed inputs and plays a critical role in buffering for downstream ecosystems.

Reallocating freshwater flow to the Florida Bay is expected to reduce hypersaline conditions, which, on the other hand, may deliver more nutrients that elevate phytoplankton blooms.

Significant evidence shows that these waters and associated nutrients can move further downstream and impact the Florida Keys National Marine Sanctuary and the Florida Keys Reef Tract. Interactions between nutrient inputs, phytoplankton blooms and sediment processes change water properties before they reach the Florida Keys, and the transport pathways and subsequent biogeochemical responses are complex. At the same time, climate change including sea level rise is modifying both oceanic boundary conditions of the regions, and watershed hydrological conditions and outputs, among other effects.

Currently, the predictive capability of these watershed impacts is limited. Most of the biogeochemical observations are through discrete water samples that are not continuous. New methods are urgently needed to synthesize all of the available sporadic observations and empirical biogeochemical theories into a coherent system for the region.

Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute have received a $350,000 grant from the United States Environmental Protection Agency to study the connectivity between the Everglades and the Florida Keys via the Florida Bay. They are developing an ocean model for the region, an innovative tool to holistically examine and diagnose key processes with numerical simulations and experiments, and to predict changes in responses to water management, ecological restoration and climate change.

“Our model, when fully developed and validated, is expected to be a powerful tool that is currently lacking for this region,” said Mingshun Jiang, Ph.D., principal investigator, physical oceanographer specializing in ocean coupled physical-biogeochemical-ecological modeling, and an associate research professor at FAU Harbor Branch. “It is designed to provide a suite of environmental and ecological information on the state of the greater Florida Bay ecosystem as well as potential future changes. Importantly, our model could potentially predict underwater aquatic vegetation coverage, harmful algal blooms, and fisheries resources under climate change and/or CERP management scenarios.”

To assist in the model development, Jiang and co-PI Laurent Chérubin, Ph.D., a physical oceanographer who specializes in the understanding of ocean dynamics and a research professor at FAU Harbor Branch, will measure currents and water quality parameters at several key locations in the Florida Bay during dry and wet seasons. They will gauge estimates of nutrients and organic export from the Florida Bay to the Florida Keys National Marine Sanctuary and the Florida Keys Reef Tract.

Jiang and Chérubin will release neutrally-buoyant (artificial) drifters from designated locations and track their trajectories to observe the movements of waters and associated pollutants. Using these drifters, they will investigate the transport and dispersion of freshwater through the Florida Bay, particularly in the northeast region. These drifters have been successfully used for studying transport and dispersion of waters in shallow waters such as Florida’s Indian River Lagoon.

Fieldwork also will include moorings of three small benthic landers each equipped with one acoustic Doppler current profiler (ADCP) and a water quality sampling and monitoring meter. Deployed at strategic locations, the researchers will measure exchanges of waters between the northeastern basin, which receives high freshwater nutrients and inputs, the southeastern basin, and water exchanges between the Florida Bay and the southwest Florida shelf where fluxes remain highly uncertain.

A new biogeochemical model will be developed to simulate nutrients (nitrogen, phosphorus) cycles, phytoplankton blooms including Karenia brevis (red tide) and cyanobacteria (blue-green algae) blooms, zooplankton, and dissolved oxygen. This model will be coupled with an existing hydrodynamic model to synthesize the observations and empirical theories. In particular, using new and historical measurements along with the new model, researchers will quantify the Florida Bay export of nutrients and organic matter and evaluate the impacts of these exports on nutrients, phytoplankton blooms and water clarity.

“New and historical data combined with our modeling will allow us to construct a full picture of connectivity of waters and associated pollutants such as nutrients, organics, and other emerging pollutants such as microplastics in this region under various conditions including wet and dry seasons as well as storms,” said Chérubin. “Results from our project will help water management agencies develop better plans for minimizing the environmental, ecological and human impacts of discharges from the Everglades as well as potentially improving habitat restoration efforts for seagrass and corals.”

Collaborators on the project include the South Florida Water Management District, Florida International University, University of South Florida, Fish and Wildlife Research Institute and NOAA’s Atlantic Oceanographic and Meteorological Laboratory.

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