The abundance and distribution of the toxic dinoflagellate,Gonyaulax tamarensis,in Long Island estuaries

The distribution and abundance of motile cells of the toxic dinoflagellateGonyaulax tamarensis Lebour were monitored in estuarine waters of Long Island, a region with no previous history of shellfish toxicity. The population distribution was patchy, with the species detected in 40% of 115 estuaries examined during the spring bloom season. More detailed studies in four estuaries indicated that the dinoflagellate was most abundant in the headwater regions, with concentrations falling to undetectable levels at the mouths.G. tamarensis cell concentrations did not exceed 10⁵ cells per 1 and often remained an order of magnitude lower. In several instances, population growth and accumulation ceased under seemingly favorable environmental and nutritional conditions.