Effects of irradiance, water temperature and nutrients on the growth of sporelings of the crustose coralline alga Lithophyllum yessoense Foslie (Corallinales, Rhodophyceae)

Abstract

SUMMARY Lithophyllum yessoense Foslie is a markedly dominant subtidal, crustose coralline alga in south–western Hokkaido, Japan. In this study, the effects of irradiance, water temperature and nutrients (nitrate and phosphate) on the growth of sporelings of the alga were examined. The relative growth rate (RGR) was saturated at 17.6% d−1 at a high irradiance (240 umol photon m2s−1). Even at a low irradiance (10.7–49.9 umol photon m−2s−1), RGR was 7.1–12.7% d−1 The survival rate of sporelings was greater than 80% at irradiance above 10.7 μmol photon m−2s−1 throughout the culture period. The growth of L. yessoense sporelings was promoted at 15°C and 20°C, but inhibited at 5°C. The half-saturation constants (Ks) for growth were about 0.5 umol L−1 and 0.14 umol L−1 for nitrate and phosphate, respectively. Saturated nitrate and phosphate concentrations for the growth were about 4.0 μmol L−1 and 0.4 μmol L−1, respectively, suggesting that L. yessoense is adaptable to a relatively high water temperature, a wide range of irradiance, and low ambient nitrate and phosphate concentrations. The results provide a possible explanation of why L. yessoense is dominant in the environments of south-western Hokkaido.