Abstract
Phytoplankton, nutrients, and physical factors in the Tampa Bay System were studied by collections taken quarterly from fall 1969, to early summer 1971. Forty-two diatom and twenty-three dinoflagellate taxa were recorded from sample aliquots. Annual averages of phytoplankton abundance
(0.78 to 1.45 × 106 cells/l) were intermediate in comparison with other estuaries of Florida and the northwestern Atlantic. Nitrate (2.31 μg-at/l), phosphate (29.16 μg-at/l), and chlorophyll + phaeopigments (16.43 mg/m3) were higher than averages
for these regions. The principal diatom was Skeletonema costatum, as in other Gulf and east-coast estuaries. The most abundant dinoflagellates were Gonyaulax balechii and Ceratium hircus. Seasonal trends for nutrients varied from area to area in the bay complex
and, on the basis of quarterly surveys, were difficult to interpret. Phytoplankton abundance in 1969-1970 was greatest in fall and least in spring in most sections of the bay. Patterns in 1970-1971 were more variable. Regionally, phytoplankton abundance and nutrient levels generally decreased
with increasing salinity toward the mouth of the bay in all seasons. Low N : P ratios throughout the year suggest that nitrogen is more limiting than phosphorus in the Tampa Bay system.