1Nagasaki Prefectural Institute of Fisheries, Taira, Nagasaki 851-2213, 2Institute for East China Sea Research, Nagasaki University, Taira, Nagasaki 851-2213, Japan
Three harmful red tide causative raphidophytes Chattonella antiqua (Hada) Ono, Chattonella marina (Subrahmanyan) Hara et Chihara and Heterosigma akashiwo Hada, and a dinoflagellate Cochlodinium polykrikoides Margalef were isolated from Isahaya Bay, Japan in 2003-2004. The growth characteristics of these four clonal cultures were examined in 60 different combinations of temperature (10-32.5°C) and salinity (16-36) under a light intensity of 80μmol/m2/s. C. antiqua reproduced at 15-32.5°C and 16-36 PSU, and the maximum growth rate was 0.99day−1 at 30°C and 32 PSU. C. marina reproduced at 12.5-32.5°C and 16-36 PSU. The maximum growth rate was 0.83 day−1, which was obtained at 30°C and 24 PSU. H. akashiwo reproduced at 10-32.5°C and 16-36 PSU. The maximum growth rate was 1.14 day−1 at 25°C and 24 PSU. C. polykrikoides reproduced at 10-32.5°C and 16-36 PSU. The maximum growth rate was 0.56 day−1 at 27.5°C and 32 PSU. Four red tide flagellates examined in this study appeared to be euryhaline. The optimum temperatures for maximum growth were different in each species and these conditions clearly corresponded with recent red tide occurrences in Isahaya Bay. Compared with growth conditions previously reported, four isolates from Isahaya Bay are likely to tolerate relatively higher temperature.