Goode!1 and Gorsline (1961) analyzed surface sediments for grain 
size, carbonates and organic carbon from all major areas of Tampa Bay 
including approximately 30 stations in Hillsborough Bay. They concluded 
that Tampa Bay sediments are a mixture of eroded quartz sands from 
Pleistocene terrace deposits and carbonates from mollusk shell fragments 
produced within the system. The present sediment distribution is 
attributed to tide generated currents. In general, sediment grain size 
increases toward the mouth of Tampa Bay and fine high organic material is 
found in the upper reaches of Hillsborough Bay and isolated areas of Old 
Tampa Bay. 
The surface sediments of Hillsborough Bay were studied intensively 
in 1968 by the Federal Water Pollution Control Administration (FWPCA 
1969). This study was conducted in cooperation with local authorities to 
suggest ways to improve the poor water quality of Hillsborough Bay. 
Ninety-five surface sediment samples throughout Hillsborough Bay were 
collected and analyzed for organic carbon, nitrogen and phosphate. A 
large area of the bay bottom (16%) contained sediments with a high 
organic carbon content of at least 3% of sediment dry weight. Highest 
organic carbon sediment concentrations were associated with discharge 
points from sewage treatment plants, river mouths, and areas deeper than 
ten feet with weak tidal currents. The most important sources of high 
organic mud were thought to be the Hillsborough and Alafia Rivers, the 
Hooker’s Point primary treatment plant, and the decomposition of settled 
phytoplankton. The nitrogen content of the sediments followed the 
distribution pattern of organic carbon, while sediment phosphate 
concentrations were highest near the mouth of the Alafia River (Flannery, 
this report). The historically low dissolved oxygen concentrations found 
in deeper waters were attributed to high benthic oxygen demands of muddy 
high organic sediments. The FWPCA (1969) recommended selective dredging 
of the extensive high organic deposits to improve Hillsborough Bay water 
quality. The recommended dredging has not been performed to this date. 
Taylor and Saloman (1969) collected surface sediments between 1961 
and 1965 from 773 locations in Tampa Bay and the adjacent Gulf of Mexico. 
Samples were analyzed for grain size composition, calcium carbonate 
content, and concentrations of organic carbon and organic nitrogen. 
Although much of Taylor and Saloman’s (1969) data remain uninterpreted, 
Taylor, Hall and Saloman (1970) used the data to relate sediment 
composition to mollusk abundance and diversity at 45 locations in 
Hillsborough Bay. Most deep stations had silty sediments and lacked 
mollusks. Areas lacking mollusks, which included several shallow sandy 
stations, were classified as unhealthy. Unhealthy areas were located 
along the eastern and western shores of the bay and near the mid-bay 
shipping channel. Healthy areas were found at the mouth of Hillsborough 
Bay and in McKay Bay. Unhealthy areas comprised 42% of the bay bottom and 
only 22% of the bottom was considered healthy. 
Doyle, Van Vleet, Sackett, Blake and Brooks (1985) analyzed 
sediment grain size composition and hydrocarbon concentration and 
distribution in Tampa Bay surface sediments during 1984 and 1985. Their 
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