4. Red Tides 
One of the most distinguishing features of Tampa and Sarasota Bays 
is their occasional entrapment of red tides, or blooms of the unarmored 
dinoflagellate, Ptvchodiscus brevis . These blooms originate in offshore 
waters of the eastern Gulf of Mexico and move onshore with Loop Current 
eddys, wind, and nearshore currents. Once inshore, the blooms 
proliferate over huge areas, at times breaking into distinct cells and 
coalescing into larger masses at other times. The blooms occur once or 
twice every year or two. While there is no evidence that the frequency 
of blooms is greater than in past years there has been speculation that 
the duration of an inshore bloom may be prolonged by nutrient enrichment 
or other factors attributable to urbanization. Blooms cause fish kills, 
defaunate the benthos, and contaminate shellfish by oxygen depletion and 
the effect of their toxic metabolites. Aerosols produced in surf 
transport toxins inland causing human respiratory distress, and blooms 
generally inhibit tourism. Much needs to be learned about bloom 
initiation, maturation and transport, and about their ecological effects. 
Benthic infauna recolonize affected areas within 1-3 years, and recovery 
by other groups probably occurs over a 1-10 year period. These naturally 
occurring blooms, which may function similarly to wildfires in Florida’s 
fire-maintained pine flatwoods, also deserve study in order to understand 
brown tides better in northeastern estuaries, which apparently are 
expressions of cultural eutrophication. 
Urban Conditions Affecting Water Quality 
Discharge of sewage treatment plant effluent and urban stormwater 
runoff pose the greatest continuing threat to water quality of Tampa Bay. 
Characteristics of STP discharge were presented at the seminar by John V. 
Betz, and Giovannel1i*s paper elsewhere in this report summarizes his 
presentation on stormwater. 
The combined role of STP effluent and stormwater --plus 
agricultural and industrial loads-- was evaluated by Palmer and 
McClelland (1988) using a numerical model. The project, funded by the 
EPA with a grant for water quality studies under Section 205(j) of the 
Clean Water Act, concluded 
The problems in Tampa Bay appear to be related to nutrient 
enrichment and consequent high algal biomass: this can 
cause large dissolved oxygen variations and decreased light 
availability needed for seagrass growth. The nutrient and 
dissolved oxygen relationship along with the data and the 
modeling indicate that a bay-wide chlorophyll a value of 
25 ug/1 should be used as a maximum target for Tampa Bay in 
order to maintain good water quality. The historical data 
show that pockets of high chlorophyll a occur in 
Hillsborough Bay and the northwest corner of Old Tampa Bay. 
The modeling indicates that reduction of the chlorophyl1-a 
in these pockets will protect the rest of the bay system. 
Therefore, if the targets are met in these pockets, the bay 
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