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Florida Bay Bottom Types
An extensive survey of bottom type in Florida Bay was conducted during the summer of 1996 and completed in January of 1997. A small, flat-bottomed boat, high resolution GPS, and snorkeling gear were used to locate and examine over 650 sites within the Bay. In areas where depth and water clarity permitted, observations from the boat along transects between survey sites were used to identify the extent of bottom types. Over 100 sediment samples were collected and analyzed for grain size, mud, water, carbonate, and organic content (Figure 1 A and B). The enclosed map represents the results of site surveys, boat transects and comparison with aerial photographs (Dec. 1994 - Jan. 1995) and SPOT satellite imagery (1987). Subregions for the Bay used here follow the recommendations of the Florida Bay Program Management Committee (1997).
Bottom Type Descriptions
The purpose of this map is to describe the bottom types found within Florida Bay for use in 1) assessing bottom friction associated with sediment and benthic communities and 2) providing a very general description for other research needs. For these purposes, two descriptors were considered particularly important, density of seagrass cover and sediment texture. Seagrass estimates are visual estimates of the amount of seagrass cover including both number of plants and leaf length. Therefore, seagrass cover may be greater in areas with long leaves than in areas with short blades, even though the number of shoots may be the same. Seagrass cover is a different measure than density (Zieman et al., 1989 or Durako et al., 1996). It is used here to more accurately reflect hydrodynamic influence than the standing crop of seagrass. Our use and definitions of dense, intermediate and sparse seagrass cover are described in the accompanying text and are similar to those used by Scoffin 1970). This map and associated descriptions are not meant to assess ecologic communities or detail sedimentological facies. The resolution of the map has been selected in an effort to define broad regions for use in modeling efforts. For these purposes, small-scale changes in bottom type (e.g. small seagrass patches) are not delineated.
Bank Top Suite
Sparse Seagrass Cover
Intermediate Seagrass Cover
Dense Seagrass Cover
Mixed Bottom Suite
In the west-central region of the Bay is an area exhibiting a highly variable bottom type. Within several meters, variations in seagrass density are extreme and open mud areas occur on what seems to be an irregular basis. Consequently, this region has been termed a mixed bottom suite. During January of 1997, large (m ) patches of seagrass, with rhizomes attached, were observed floating in the area. The patches appeared to be eroded at their edges, and portions of the seagrass mat were peeling off the sediment surface.
Open Sandy Areas
Areas of open sandy bottom occur in the Gulf transition zone of the Bay. These areas are distinct from hardbottoms in that no significant benthic life is present and the sediments are coarse shelly carbonate sands. One large area of east-west running open sand occurs just south of Cape Sable, it is most likely an erosional product of strong tidal flow within the area.
Figures 1 A and 1B
Bosence, D. 1989. Surface Sublittoral sediments of Florida Bay, Bull. Mar. Sci. 44(1):434-453.
Durako, M. J., Hall, M, and Hall, J. 1996. The status and trends of seagrass communities in Florida Bay, In: Programs and Abstracts, 1996 Florida Bay Science Conference, Key Largo, FL: 34-36.
Florida Bay Program Management Committee. 1997. Strategic plan for the interagencey Florida Bay science program, available from Everglades National Park.
Ginsburg, R. N. 1956. Environmental relationships of grain size and constituent particles in some south Florida carbonate sediments. Bull. Am. Assoc. Petrol. Geol. 40(10): 2384-2427.
Scholl, D. W. 1996. Florida Bay: A modern site of limestone formation, in Fairbridge, R. W., ed., Encyclopedia of the Earth Sciences, New York, McGraw Hill Book Co.: 282-288.
Zieman, J. C., Fourqurean, J. W., and Iverson, R.L. 1989. Distribution, abundance and productivity of seagrass and macroalgae in the Florida Keys. Bull. Mar. Sci. 44(1): 292-311.
The authors wish to thank NOAA's National Undersea Research Center in Key Largo, the Florida Keys Marine Laboratory on Long Key, and the National Park Service for facilities support. The National Park Service also provided access to SPOT imagery. Our thanks also to Mike Durako, Hal Wanless, Dave Rudnick, Paul Carlson, Bill Lyons and Jim Fourqurean for their review and helpful comments. Additional gratitude is extended to Mark Hansen, Rita Byrd, and Cherie Hulsman-Reid for their mapping skills and perseverance.
This map is preliminary and has not been reviewed for conformity with the USGS editorial standards (and stratigraphic nomenclature). Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS.
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For more information contact:
SOFIA Project: Sedimentation, Sea-Level Rise and Circulation in Florida Bay
U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 04 September, 2013 @ 02:04 PM (KP)
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