CONCLUSION 
The soft, muddy, high organic sediments and their associated fauna 
found in Hillsborough Bay are important for nutrient regeneration and 
oxygen demand. These processes appear to be related to the water quality 
and "health" of the bay ecosystem. The location and areal coverage of the 
soft sediments is relatively well known (see above). Sub-bottom profiling 
by the BSG in 1986 revealed that the soft sediment deposits in central 
Hillsborough Bay may be thicker than 3m in some places. However, the 
recent history and accumulation rate of these sediments is largely 
unknown. 
Doyle et al. (1985) carbon dated the bottom of sediment cores at 
five locations in Tampa Bay including one taken in Hillsborough Bay. We 
used this information and calculated an average sedimentation rate over 
the length of the cores of only 6.0 cm/100 yr. However, this rate may not 
represent sedimentation occurring in the soft areas of central 
Hillsborough Bay, since all cores, except one anomalous core from middle 
Tampa Bay, were taken in sandy sediments. We know that fine sediments 
accumulate rapidly in recently dredged areas with limited circulation. 
For example, rates of 10 cm/yr or more have occurred in Bayboro Harbor 
(Young 1984), a small mid-Tampa Bay embayment, and The Kitchen, located 
in southeastern Hillsborough Bay. 
A detailed study to determine geologically recent sedimentation 
patterns of soft sediments in Hillsborough Bay is presently being planned 
between the BSG and the University of South Florida Marine Science 
Department. The study will attempt to identify controls and processes 
governing recent sedimentation in Hillsborough Bay, including 
anthropogenic impacts by analyzing core samples. A similar study of 
contaminated soft sediments found in the lower Hillsborough River has 
been initiated by the COT Stormwater Division in cooperation with the 
Florida Institute of Technology. 
Information on surface sediments and their relationship to the 
nutrient budget and water quality conditions of Hillsborough Bay is 
critical to realize possible management options for this stressed marine 
ecosystem. Recent improvements in Hillsborough Bay water quality (HCEPC 
1987 and COT 1988) appear related to recent reductions in nutrient 
loadings from sewage (Garrity, McCann and Murdoch 1985) and fertilizer 
industry effluents (Estevez and Upchurch 1985). To effectively alleviate 
eutrophic conditions of an estuary, efforts should be aimed at decreasing 
point and non-point nutrient inputs. Point and non-point nutrient inputs 
may ultimately be the cause of high organic sediments deposits. The 
removal of high organic containing sediment would only result in a short 
term reduction of sediment nutrient inputs. Other nutrient inputs, left 
unchecked, would recreate the high organic sediment deposits previously 
removed. Consequently, costly management undertakings, such as selective 
dredging of these deposits (see FWPCA 1969), may never be needed and must 
be avoided until potential impacts from these sediments on the Tampa Bay 
ecosystem are better understood. 
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