During the first year (1994-1995) of funding, we used stratified sequences from four sites to evaluate the potential for detailed dating and paleoenvironmental reconstruction of areas adjacent to Florida Bay which influence or reflect the environments of Florida Bay. A three-core sequence was recovered which represented a freshwater to coastal-salinity gradient from the mouth of Shark River Slough (mouth of Avocado Creek) through lower Shark River (a laminated filled bay sequence in adjacent Whitewater Bay) to Ponce de Leon Bay (laminated bank in the northeastern sector) (Figure 1, Cores 1,2,& 3). This transect has the potential to represent the changing influence of discharge from Shark River Slough to the adjacent marine environment. A fourth layered sediment site in northwestern Coot Bay (Figure 1, Core 4) has provided an opportunity to evaluate how the sediment sequence has recorded known historical changes and influences (opening and closing of Coot Bay Canal connection with Florida Bay; Hurricane of 1935 and 1960).
Used as a first-cut quality-control procedure, X-radiographs of each core were made and evaluated for sediment disruption (bioturbation...) and lamination. X-radiography indicated extensive lamination in all cores and thus interpretable sedimentary sequences for those analyzed in detail for chemical, biological and physical parameters. Initial geochronology, for Core 9410 (Core 2, Figure 1), indicate that sediments from this core represent >100 yrs and thus potentially record natural and anthropogenic events over the time scale of interest to our study.
Core 9410 is being analyzed for community characterization of foraminifera, ostracodes, and algae. Results to date indicate that 16 species of foraminifera and 28 species of ostracoda have been indentified. Initial results with ostracodes indicate that various aspects of their community and physiological structure will be valuable (paleo-)salinity indicators. Major shifts in foram community structure are not dramatic, however within the Elphidium genus and the milliolids, significant species shifts were observed and the significance of this is being evaluated.
Ongoing analyses for diatoms and microsclera are at present limited, although some early results can be summarized by species shown in Figure 2. Diatoms, such as Campylodiscus sp. (Figure 2A) exhibit a benthic lifestyle. Benthic diatoms in shallow-water environments, such as Florida Bay, are typically euryhaline. In addition, larger centric diatoms, such as Biddulphia sp. (Figure 2B) can often be useful as a productivity indicator. Microsclera are microscopic siliceous sponge spicules useful in taxonomic studies. They are scattered throughout the tissue or concentrated in an extosomal layer, and are formed for structural support. Both selenasters ( Placospongia sp., Figure 2C) and sterrasters (Geodia sp. Figure 2D) are significant contributors to the biogenic component of the sediments in Whitewater Bay.