Projected Reorganization of Florida Bay Seagrass Communities in Response to the Increased Freshwater Inflow of Everglades Restoration
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Historic changes in water-use management in the Florida Everglades have caused the quantity of freshwater inflow to Florida Bay to decline by approximately 60% while altering its timing and spatial distribution. Two consequences have been (1) increased salinity throughout the bay, including occurrences of hypersalinity, coupled with a decrease in salinity variability, and (2) change in benthic habitat structure. Restoration goals have been proposed to return the salinity climates (salinity and its variability) of Florida Bay to more estuarine conditions through changes in upstream water management, thereby returning seagrass species cover to a more historic state. To assess the potential for meeting those goals, we used two modeling approaches and long-term monitoring data. First, we applied the hydrological mass balance model FATHOM to predict salinity climate changes in sub-basins throughout the bay in response to a broad range of freshwater inflow from the Everglades. Second, because seagrass species exhibit different sensitivities to salinity climates, we used the FATHOM-modeled salinity climates as input to a statistical discriminant function model that associates eight seagrass community types with water quality variables including salinity, salinity variability, total organic carbon, total phosphorus, nitrate, and ammonium, as well as sediment depth and light reaching the benthos. Salinity climates in the western sub-basins bordering the Gulf of Mexico were insensitive to even the largest (5-fold) modeled increases in freshwater inflow. However, the north, northeastern, and eastern sub-basins were highly sensitive to freshwater inflow and responded to comparatively small increases with decreased salinity and increased salinity variability. The discriminant function model predicted increased occurrences of Halodule wrightii communities and decreased occurrences of Thalassia testudinum communities in response to the more estuarine salinity climates. The shift in community composition represents a return to the historically observed state and suggests that restoration goals for Florida Bay can be achieved through restoration of freshwater inflow from the Everglades.
KeywordsEcosystem restoration Florida Bay Everglades Benthic habitat Seagrass Water quality Salinity Hydrology Modeling
The monitoring programs that supplied vital benthic habitat data for this effort included the South Florida Water Management District/Miami-Dade County Department of Environmental Resources Management funded monitoring program, the Florida Keys National Marine Sanctuary funded by grants from NOAA’s South Florida Program (contract NA06NOS4780105) and the US EPA (Assistance Agreement X797468102), and Florida Department of Environmental Protection’s Fish Habitat Assessment Program funded by Florida DEP, USGS Biological Resources Division, and Everglades National Park. Funding for analyses were provided by grants from Everglades National Park, Critical Ecosystems Studies Initiative (Cooperative agreement 1443CA528001022), and Florida Sea Grant (SI-08-33). Water quality data were made available by J.N. Boyer at Florida International University. Further support was provided by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Grant No. DBI-0620409 and Grant No. DEB-9910514. This is publication number 514 from the Southeast Environmental Research Center at FIU.
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