BIOLOGY AND EUTROPHICATION OF TAMPA BAY 
Roy R. Lewis III 
Mangrove Systems, Inc. 
Tampa, Florida 
BIOLOGICAL CHARACTERISTICS 
Primary Producers 
There are four principal groups of phytoplankton in Tampa Bay: 
phytomicroflagel1ates, diatoms, dinoflagellates and blue-green algae. 
The early studies of phytoplankton in the bay have been summarized by 
Steidinger and Gardiner (1985). These studies were initiated in response 
to the problem of blooms (cell counts usually greater than 50,000 per 
liter) of toxic dinoflagellates ( Ptvchodiscus brevis ). known as "red 
tides", particularly the massive blooms of 1946-1947. The findings of 
all studies to date can be summarized as follows: 
1. A north-to-south, or head-to-mouth, gradient exists in 
phytoplankton species numbers. In general, as one moves from the 
less saline upper portions of the bay to the more saline lower 
portions of the bay, water clarity and phytoplankton species 
numbers (or "richness") increase, while nutrient levels, 
chlorophyll ’a’, and total phytoplankton cell counts decrease. 
The frequency of phytoplankton blooms and the eutrophic and turbid 
nature of the upper bay, particularly Hillsborough Bay, have been 
a common observation in recent years (Federal Water Pollution 
Control Administration [FWPCA] 1969; Simon 1974). 
2. Nanoplankton (5-20 urn) generally are the dominant size class of 
the phytoplankton. Small diatoms and mi crofl agel 1 ates 
predominate, except when certain seasonal, monospecific blooms of 
species of blue-green algae ( Schizothrix ) or dinoflagellates 
( Gvmnodinium nelsonii , Ceratium hircus . Procentrum micans , 
Gonvaulax spp. and others) dominate in Hillsborough Bay and Middle 
Tampa Bay. 
3. At least 272 species of phytoplankton occur in the bay: the 
majority (167) are diatoms. 
4. Short-term fluctuations in species composition and standing crop 
are common. Seven-fold to ten-fold differences are reported 
within one tidal cycle. 
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