Growth response and toxin concentration of cultured Pyrodinium bahamense var. compressum to varying salinity and temperature conditions

Abstract

The growth and toxin production of a Philippine Pyrodinium bahamense isolate in nutrient replete batch cultures were investigated under conditions affected by varying salinity, temperature and combined effects of salinity and temperature. Early exponential growth stage was reached after 7 days with a cell division rate of 0.26 div day-1. The toxin content reached a peak of 298 fmol cell-1 at mid exponential phase and rapidly declined to 54 fmol cell-1 as it approached the death phase. Only three sets of toxins composed of STX, dcSTX and B1 were detected in which STX made up to 85-98 mol% toxin cell-1. P. bahamense was able to grow in salinities and temperatures ranging from 26‰ to 36‰ and 23 to 36 °C, respectively. The optimum growth under varying salinity and temperature conditions was observed at 36‰ and 25 °C. Toxin content reached a peak of 376 fmol cell-1 at 25 °C and was lower (80-116 fmol cell-1) at higher temperatures (32-35 °C). Combined effects of salinity and temperature showed that P. bahamense was not able to grow at low salinity and temperature (i.e. below 26‰-28 °C). Optimum growth was observed in higher salinities at all temperature conditions. © 2007 Elsevier Ltd. All rights reserved.