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 (5–30°C) and salinity (10–35 PSU). Heterocapsa circularisquama did not grow at or below a temperature of 10°C. The maximum growth rate of H.circularisquama (1.3 divisions day−1) was obtained with a combination of 30°C and 30 PSU. In contrast, C. verruculosa did not grow at 10 PSU and at temperatures of 25°C or more. The maximum growth rate of C. verruculosa (1.74 divisions day−1) was obtained with a combination of 15°C 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 pre viously unaffected waters.