Observations on the Factors Involved with Fish Mortality as the Result of Dinoflagellate “Bloom” in a Freshwater Lake

Complete fish mortality associated with the development of high populations of dinoflagellates (Gymnodinium spp.) was observed in 1960 in a 9.5 acre fresh-water lake at Baton Rouge, Louisiana. Toxicity of the water samples containing the algae appeared to be related to the increased pH, length of exposure to sunlight and concentration of algal cells. Filtration with activated carbon removed the toxic effects. Laboratory tests offered data to explain the course of the fish mortality in the lake.