Woolfenden (1985) listed red tides, parasite outbreaks, dredge and fill 
activities, pesticide use, and oil spills as having generally negative 
effects on bird abundance. Waterfowl surveys of the bay have indicated a 
sharp deline in the winter population of Lesser Scaup, from 105,900 in 
1976 to 8,400 in 1979. Major dredging in Hillsborough Bay is implicated 
as a possible cause of the decline, because over 400 ha of open water 
habitat was lost during this period as a consequence of spoil island 
creation. 
Reynolds and Patton (1985) have summarized the existing 
information on marine mammals of the Tampa Bay area. Only two species 
are normally found within the bay, the bottlenose dolphin ( Tursiops 
truncatus ) and the West Indian manatee ( Trichechus manatus ). The 
bottlenose dolphin is a year-round resident and the local population is 
estimated at 100-200 individuals, found in small herds of three to six 
animals (Reynolds and Patton 1985). 
In a baywide survey over a period of one year, Patton (1980) found 
that numbers of manatees varied seasonally; a maximum of 55 was observed 
in the winter. They appeared to congregate around industrial thermal 
discharges into the bay. The largest single aggregation was 42 
individuals, observed around the mouth of the Alafia River in February 
1980. Lewis et al. (1984) observed manatees feeding on macroalgae in the 
same area in January 1981. 
There is a general absence of studies on ecological relationships 
in the bay. Unlike studies in Apalachicola Bay (Livingston 1984), most 
scientific work in Tampa Bay has been basically descriptive, or has 
concentrated on a single structural or functional aspect of the bay’s 
ecology. Future studies need to address four topics concerning 
ecological relationships in the bay: 1) energy sources; 2) abiotic 
controls in communities; 3) plant and animal interactions; and 4) 
fisheries habitats. 
The flow of energy from the sun through plants to the animal 
communities of the bay is illustrated in Figure 5. None of the boxes or 
arrows have numbers associated with them because the specific quantities 
of energy contributed to the various animal groups by the major plant 
types have not been made. Table 1 lists phytoplankton as the source of 
68.8% of the bay’s primary production. This does not mean that 
phytoplankton provide 68.8% of the energy consumed by animals in the bay, 
because the quantity of energy captured by phytoplanktonic photosynthesis 
that is subsequently lost to sedimentation and flushing to the bay is 
unknown. Because of eutrophication, it is likely that much phytoplankton 
productivity is incorporated as organic deposits in the bottom of the 
bay, and may contribute to anoxic conditions reported in Hillsborough Bay 
(Johansson and Squires, this volume). Similar events have been 
attributed to high phytoplankton productivity in Chesapeake Bay (Officer 
et al. 1984). 
103 
