Effects of temperature and salimty on growth of Thalassiosirap seudonana (Bacillariophyceae) isolated from ballast warer

Abstract

The aim of this study was to assess the role of ballast water discharge as a vector for the introduction of exotic species into Korean coastal and river waters. We examined the impacts of environmental factors on the survival success of ballast water introduced planktonic organisms, and also describe the effects of temperature and salinity on growth of the centric diatom Thalassiosira pseudonana. On the salinity gradient experiments for natural phytoplankton communities of the vessel Daewoo Diamond, several freshwater and marine species were successfully identified. Of these, T. pseudonana was the dominant species in all salinity conditions (0 to 30psu). In combination experiments of temperature and salinity on T. pseudonana monoculture, the organism did not grow between 5 and 10°C in freshwater culture media, but exhibited the ability to grow in low temperatures (5°C) in brackish and marine water. Furthermore, T. pseudonana cells grow significantly with increasing of temperature (10-30°C) in media of brackish and marine water. Our result indicates that T. pseudonana is well adapted to euryhaline and eurythermal conditions and its species-specific viability was suitable for successful colonization into local Korean aquatic ecosystems.