EFFECT OF TEMPERATURE, SALINITY AND LIGHT-INTENSITY ON THE GROWTH AND SEASONALITY OF TOXIC DINOFLAGELLATES ASSOCIATED WITH CIGUATERA

In laboratory unialgal culture experiments, eight species of toxic dinoflagellates associated with ciguatera, Gambierdiscus toxicus Adachi et Fukuyo, Prorocentrum lima (Ehrenberg), Dodge, P. concavum Fukuyo, P. mexicanum Loeblich, Shirley et Schmidt, Coolia monotis Meunier, Amphidinium klebsii Taylor, Ostreopsis heptagona Norris, Bomber et Balech, and O. siamensis Schmidt were grown under various temperatures, salinities and light intensities. Three different groups emerged due to optimum temperature differences: a cool-water (25-degrees-C) group consisting of both Ostreopsis species, a warm-water (29-degrees-C) group containing G. toxicus and C. monotis, and a median-water (26-28-degrees-C) group consisting of the three Prorocentum species and A. klebsii. Salinity optima for all species examined except P. mexicanum were < 35 parts per thousand. All species examined except P. concavum and C. monotis had light intensity optimums of < 10% full sun light. The optimal growth conditions determined in the laboratory were compared to the seasonality in the Florida Keys, USA. Differences in temperature, salinity, and light intensity optima for the various species may result in variations in species ratios which may account for differences in the symptomatology in humans suffering from ciguatera.