Effects of temperature, salinity and their interaction on growth of the benthic dinoflagellate Ostreopsis cf. ovata (Dinophyceae) from Japanese coastal waters

Abstract

Benthic dinoflagellates of the genus Ostreopsis produce palytoxin (PTX)-like compounds. The worldwide distributed Ostreopsis ovata/O. cf. ovata is potentially responsible for outbreaks of human health problems around the coasts of tropical, subtropical, and temperate regions. The present study examined growth responses of an O. cf. ovata strain s0662 collected from coastal waters of Japan with 35 different combinations of temperature (15-35°C) and salinity (20-40) and discusses the bloom dynamics of the organism in Japanese coastal environments. The O. cf. ovata strain s0662 tolerated a wide range of temperature (17.5-35°C) and salinity (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). Results of a two-way ANOVA showed significant effects of temperature-salinity interaction on growth rates and biomass yields of the O. cf. ovata strain (F(24,70) > 127, P < 0.001). The strain showed a maximal growth rate (1.03 divisions day -1 ) and biomass yield (240 relative fluorescence) at temperature 25°C and salinity 30. The high growth rates of over 1.0 division day -1 were obtained in conditions of temperature 25-30°C and salinity 30-35, which indicates that strain s0662 prefers high temperature and salinity conditions. The growth rates of O. cf. ovata under the optimal conditions were higher than those of other benthic toxic-dinoflagellates, Coolia monotis, Gambierdiscus toxicus, and Prorocentrum lima (Dinophyceae) previously reported. Taken together, we suggest that O. cf. ovata is able to grow faster than the other benthic dinoflagellates in waters of high temperature and salinity. The physiological feature probably confers an ecological advantage on O. cf. ovata in the bloom development during warmer seasons in Japan and may be responsible for outbreaks of PTX-like poisoning in the region especially during the warmer seasons.

Effects of temperature, salinity and their interaction on growth of benthic dinoflagellates Ostreopsis spp. from Thailand

“…proliferation (Morton et al, 1992;Mangialajo et al, 2011;Pistocchi et al, 2011;Fraga et al, 2012;Tanimoto et al, 2013;Yamaguchi et al, 2012a). Results obtained from statistical analyses in this study demonstrated that the effect of temperature on growth of Thai Ostreopsis species/clade/subclades was stronger than those of salinity and temperature-salinity interaction.…”

“…Following a previously reported method (Yamaguchi et al, 2012a;Yoshimatsu et al, 2014), the tested strains were cultured in duplicate PP-capped 50-mL glass test tubes (25 mm  150 mm) with a flat bottom containing f/2 medium in a growth chamber (MLR-351; Sanyo Co., Ltd, Japan) at 25 8C, salinity 30, and light intensity 90-100 mmol photons m À2 s À1 of cool white fluorescent illumination on a 12:12 h L:D cycle. The factorial design of experiment concerned two main effects, temperature (20, 25, 30, 32.5, 35 8C) and salinity (20,25,30,35,40).…”

“…The average growth rate (m: divisions day À1 ) of Ostreopsis spp. was calculated by following the method of Yamaguchi et al (2012a). If the observed fluorescence of the culture at a temperature and salinity regime declined from the initial value, the growth rate showing a minus value was evaluated as no growth and was expressed as a growth rate of zero (0 divisions day À1 ).…”

“…Then, the cultures were transferred to each treatment combination using a temperature gradient growth chamber (TG-100-AD; Nippon Medical & Chemical Instrument, Japan) and growth cabinet (MLR-350; Sanyo, Osaka, Japan). The salinity used in this study was adjusted by following the protocols of Yamaguchi et al (2012a) and Yoshimatsu et al (2014). Inoculum size was adjusted giving <1% (v/v) of pre-cultures.…”

“…Grané li et al (2011 also reported that an O. ovata strain from the Tyrrhenian Sea showed high growth rates under high water temperature (26-30 8C) conditions. Yamaguchi et al (2012a) reported that O. cf. ovata from Japanese coastal waters showed high growth rates of more than 1.0 division day À1 in temperatures of 25-30 8C.…”