Salinity Effects on Growth and Toxin Content of Gonyaulax Excavata. A Marine Dinoflagellate Causing Paralytic Shellfish Poisoning1

The optimum salinity for growth of Gonyaulax excavata (Braarud) Balech from Cape Ann, Massachusetts, is 30.5%o, and it grows well over a range of 20–40%o.It tolerates salinities of 11–43%o. Growth rates at 24 and 20%o are only ca. 10 and 20% less, respectively, than the maximum, 036 divisions/day. It is considered unlikely that salinity fluctuations in the coastal areas where this organism occurs significantly influence its growth rate. The paralytic toxin content in G. excavata increases with increasing salinity, up to 37%o. Therefore, the degree of toxicity of the organism in nature may be influenced by this environmental factor.