Mass mortality of fish associated with the Protozoan Gonyaulax in the Gulf of Mexico.

This paper represents the first reported observation of the concurrent appearance of a red tide, luminescent water, and immense numbers of the dinoflagellate protozoan, Gonyaulax, with mass mortality of fish on the eastern coast of North America. The episode occurred in the summer of 1949 in a salt water lagoon known as Offatt Bayou along Galveston Island. Three previously unreported associated biochemical phenomena were revealed by water analyses and offered new clues to the mechanism of fish mortality: (1) There were indications that small amounts of sewage pollution favored the growth of the protozoan. (2) Extraordinarily wide and rapid variations in the dissolved oxygen content of the water were observed during and immediately following heavy concentrations of Gonyaulax. (3) The values of biochemical oxygen demand (BOD) for the samples associated with Gonyaulax were extraordinary and far in excess of what might be explained by sewage or any other organic pollutant entering the bayou.