Observations on the 1971 Summer Red Tide in Tampa Bay, Florida

A 3½ month summer red tide (Florida west coast) caused by the unarmored dinoflagellate, Gymnodinium breve, is described and discussed. Observations support the following: 1) estuaries normally present a low salinity barrier to this neritic species, 2) heavy cell concentrations are aided by physical factors rather than increased cell division, 3) inshore and near-shore reef fisheries are the only ones affected and then only temporarily, and 4) commercial bivalves are safe for human consumption 1–2 months after a red tide has ended. Further it is suggested that 1) G. breve may bloom from a resident cyst population, 2) pollution does not trigger a Florida red tide, 3) G. breve probably blooms almost annually, and 4) major Florida red tides can be predicted by monitoring programs.