Effects of temperature, salinity and irradiance on the growth of the red tide dinoflagellate Gyrodinium instriatum Freudenthal et Lee

The effects of temperature, salinity and irradiance on the growth of the red tide dinoflagellate Gyrodinium instriatum Freudenthal et Lee were examined in the laboratory. Exposed to 45 different combinations of temperature (10-30 degrees C) and salinity (0-40) under saturating irradiance, G. instriatum exhibited its maximum growth rate of 0.7 divisions/day at a combination of 25 degrees C and a salinity of 30. Optimum growth rates (>0.5 divisions/day) were observed at temperatures ranging from 20 to 30 degrees C and at salinities from 10 to 35. The organism could not grow at <= 10 degrees C. In addition, G. instriatum burst at a salinity of 0 at all temperatures, but grew at a salinity of 5 at temperatures between 20 and 25 degrees C. It is noteworthy that G. instriatum is a euryhaline organism that can live under extremely low salinity. Factorial analysis revealed that the contributions of temperature and salinity to its growth of the organism were almost equal. The irradiance at the light compensation point (I(o)) was 10.6 mu mol/(m(2) s) and the saturated irradiance for growth (I(s)) was 70 mu mol(m(2) s), which was lower than I(s) for several other harmful dinoflagellates (90-110 mu mol/(m(2) s)). (C) 2005 Elsevier B.V. All rights reserved.