THE EFFECT OF SALINITY ON GROWTH OF GYMNODINIUM BREVE DAVIS

Abstract

1. Bacteria-free Gymnodinium breve were exposed to media with salinity values ranging from 6.3 to 46.0%o; the best growth occurred between 27 and 37%o. These results indicate G. breve to be a relative stenohaline dinoflagellate. 2. Field evidence associates high incidence of dense populations with salinity levels a few parts per thousand below those of the offshore waters of the Gulf of Mexico. Our results suggest that this field distribution does not represent a salinity requirement per se, since salt concentrations equivalent to those of the open Gulf did not inhibit growth of this organism in culture. 3. No instances of optimal growth occurred in culture media with salinity levels of 24%o or less. Under equivalent estuarine conditions salinity may be a limiting factor in the natural distribution of G. breve.