Red Water Bloom of a Dinoflagellate in Hillsborough Bay, Florida

Abstract

WATERS of Tampa Bay, Florida, are regularly sampled for plankton in connexion with studies of the Florida red-tide organism (Gymnodinium breve, Davis) and estuarine ecology. On May 5, 1964, various division stages and chain formations of an armoured dinoflagellate, Ceratium furca (Ehrenberg), were detected in the surface waters of Hillsborough Bay, an upper arm of Tampa Bay. The water samples were tinted brown and contained an average count of 2.294 × 10⁵ cells of C. furca per litre. Two weeks later, during an aerial survey of Tampa Bay, two staff biologists noticed patches of blood-red water in the upper-portion of Hillsborough Bay. On May 25, during a special cruise in Hillsborough Bay, water in the entire upper portion of the Bay was discoloured with brownish and reddish patches. The most intense discoloration was noticed in areas protected from the wind. No mortality of fish or any other organism was observed in the field. Blue crabs, Callinectes sapidus Rathbun, and scaled sardines, Harengula pensacolae Goode and Bean, were actively swimming through the patches of blood-red water without showing ill effects.