Phytoplankton viability in ballast water from international commercial ships berthed at ports in Korea

We investigated the viability of phytoplankton from ballast water of international commercial ships berthed at the ports of Ulsan and Onsan, Korea. The incubation conditions used were temperatures of 13 degrees C to represent ambient water and 20 degrees C to represent the thermal optimum, as well as nutrients in ballast water, shipside water, and F/2 medium. Phytoplankton in new (approximately 7 days) and old (20 and 2 days) ballast water survived when incubated under the nutrients typical of shipside water and F/2 medium at 13 degrees C and 20 degrees C. Colonization process was mostly dominated by Skeletonema costatum, Cylindrotheca closterium and pennate diatoms (<10 microm in diameter). S. costatum and C. closterium were persistent during incubation time, whereas pennate diatoms dominated in the three types of media from doubling to last phase of growth. This study showed that bloom-forming and pennate diatoms appear to be the species most likely to become successfully established in the two ports.