Lawrence Rozas, Edward Matheson (FL, DEP), Michael Robblee (USGS), and Gordon Thayer (NMFS Beaufort, NC)

Florida Bay is characterized by a series of basins separated by carbonate mud  banks and mangrove keys.  Salinity within  basins varies both seasonally and spatially across Florida Bay.  Hypersaline conditions often occur, especially in Central Florida Bay and during periods of low rainfall.  To varying degrees, hypersalinity is caused by combined slow circulation and high evaporation as well as by water management practices upstream of Everglades National Park.

Florida Bay, patchy sea grass beds

Healthy turtlegrass beds in Florida Bay being investigated

Hypersaline conditions and poor circulation are thought to have contributed to a recent episode of seagrass mortality in Florida Bay.  In response to the loss of seagrass across large areas of the bay, the South Florida Water Management District and the U.S. Army Corps of Engineers initiated a program to increase freshwater flow into Taylor Slough and the central basins of Florida Bay in July 1993.  The purpose of our research is to assess fishery organisms and seagrass habitats along a salinity gradient within Florida Bay and to evaluate the community response to this experimental increase in freshwater delivery to the bay.  Our objective is to quantify and compare densities of fishes and decapods in seagrasses among three zones of Florida Bay having different salinity regimes and responses to increased freshwater inflow.

We are quantifying and comparing animal densities in seagrass across three zones and among three habitat types (basin, near-key, and bank) in Florida Bay.  Comparative sampling using 1-m 2throw traps is conducted twice annually during the wet season (August-October) and in the dry season (March-May).  Eighteen key-basin locations are sampled each season.  Numbers and biomasses (wet weight) of fishes and decapods are measured at five replicate sites randomly located in seagrasses within each habitat type at each key-basin location.  At each sample site, temperature, salinity, and above-ground biomass of seagrasses are being measured with each faunal sample.  Seagrass composition and biomass also are estimated at each site by clipping seagrass shoots from within a sample quadrat.  Our research results will be used to assess the immediate and longer term effects of experimental water manipulation on faunal use of seagrass beds.

The study area was sampled in fall 1998, spring and fall 1999, and spring 2000.  Most of the nekton samples have been sorted and animals contained in these samples are currently being identified.  We anticipate that the identification of organisms in all samples will be completed by summer 2001.  Data analyses will be completed between spring 2001 and spring 2002.  Manuscripts reporting the results of our study will be prepared and submitted for publication between spring 2001 and summer 2002.