Effects of temperature and salinity on the growth of the red tide flagellates <i>Heterocapsa circularisquama</i> (Dinophyceae) and <i>Chattonella verruculosa</i> (Raphidophyceae)

Abstract

Growth responses of the red tide flagellates, Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae), were examined with 36 different combinations of temperature (5-3OC) and salinity (10-35 PSU). Heterocapsa circularisquama did not grow at or below a temperature of 10C. The maximum growth rate of H.circularisquama (13 divisions day 1 ) was obtained with a combination of 30C and 30 PSU. In contrast, C. verruculosa did not grow at 10 PSU and at temperatures of 25C or more. The maximum growth rate of C. verruculosa (1.74 divisions day 1 ) was obtained with a combination of 15C and 25 PSU. A significant temperature-salinity interaction on growth was found by factorial analysis. Based on the physiological characteristics obtained in the present study, these novel flagellates have a potential for future outbreaks of red tides in previously unaffected waters.