The response of Gymnodinium breve to municipal waste materials

The response of the unarmored dinoflagellate Gymnodinium breve, which is the causative organism in catastrophic fish kills along the Florida Gulf coast, to enrichment with selected inorganic nutrients, municipal waste materials, and various detergent components has been determined. The biostimulatory effects of the various enrichments were determined by a modification of the Provisional Algal Assay Procedure of the Joint Industry/Government Task Force on Eutrophication. Inorganic nutrients (orthophosphate, nitrate, and ammonia) were added individually and in combination, and the results were compared to equivalent enrichments with the effluent from a secondary sewage-treatment plant. The maximum cell population, Nmax, attained could be increased 3-fold by the sew-age-treatment plant effluent or by the equivalent combination of inorganic nutrients; individually, however, the inorganic nutrients had no pronounced effect on maximum cell population, Nmax (except for a 30% increase produced by slight orthophosphate enrichment). The results of these studies indiccate that, at concentrations of orthophosphate typical of Florida coastal waters (ca. 0.10 ppm), the growth-promoting potential (as reflected by Nmax) of the medium was a linear function of the ammonia-nitrogen concentration (0.01 to 0.11 ppm). The sewage-treatment plant effluent was presumably low in detergent phosphate, having been obtained from a treatment plant some 6 months after the enactment of a ban on phosphate-containing detergents. Additions of orthophosphate or detergent-phosphate to the treatment-plant effluent did not significantly increase the observed biostimulatory effect of the waste material.