Gregg R. Brooks

Hillsborough Bay is the northeast lobe of Tampa Bay, the largest open water estuary on Florida's west coast. For a complete description of the setting and previous works, the reader is referred to Doyle, et al. (1989). The Phase I study of fine-grained sediments in Hillsborough Bay (Brooks and Doyle, 1989) established distribution patterns and average accumulation rates of mud-dominated sediments at selected sites within the Bay over the past several thousand years. Phase II of the study, the focus of this investigation concentrates on the uppermost 50-100 cm. of the sediment column, or those sediments believed to have been deposited within approximately the past 100 years. Objectives of this study were to investigate depositional patterns and accumulation rates of sediments deposited during the period of man's presence in the Bay area; compare results with historic patterns identified during Phase I; and, evaluate the extent to which man's activities have impacted Bay sediment distribution patterns and accumulation rates. Since sedimentary deposits record the recent development and activities affecting the Bay, results will be important for determining the overall impact that man's acitivites have had on the Hillsborough Bay ecosystem, which should prove useful for more effective Bay management.

The primary objective of this project, one phase of a potentially larger investigation on sediments of Hillsborough Bay, was to determine vertical distribution patterns of mud-dominated sediments. Vertical distribution patterns represent the recent geologic history of the study area. For this project the term 'recent geologic history' refers to the past several thousand years, or the period since being flooded by the Holocene rise of sea level.

The primary purpose of this project was to establish and characterize, as far as possible, hydrocarbon base levels for the Tampa Bay Estuary. In addition, we were to characterize 1) hydrocarbon molecular compositions, 2) the isotopic composition of total and lipid sediment organic carbon, and 3) evaluate the potential for utilizing isotopic analyses to quantify and determine the extent of future oil spills.