RED WATER IN LA JOLLA BAY, 1964–19661

Abstract

Five red water dinoflagellate blooms took place in La Jolla Bay, California, between May 1964 and Deeember 1966. Predominant organisms were Gymnodinium spp. and Cochlodinium spp. (May 1964), Prorocentrum micans (April 1965) and Gonyaulax polyedra (June–July 1964, June—July 1965, and December 1966). Cell concentration and chlorophyll a content were measured during each bloom with values up to 20 × 106 cells/ liter and approximately 500 µg chlorophyll a/liter. During the day, the organisms appeared in discrete patches that apparently dispersed at night. Cell carbon and nitrogen content of the organisms often exceeded that available in surface waters or in the water column. Cells must be concentrated both vertically and horizontally to account for the numbers observed in patches during the day. Even in the densest patches the cells appeared to be physiologically active based upon measurements of photosynthetic rate, nitrate reductase activity, and observed motility. Decline of blooms was associated with increases in dissolved organic carbon, orthophosphate and monophosphate esters. The May 1964 bloom was decimated by grazing of Polykrikos sp., Noctiluca sp., and rotifers. A steep shallow thermocline was associated with the blooms.