Appearance and characteristics of major phytoplankton species based on long-term monitoring datasets in southern sea of Korea.

ABSTRACT

To understand the mechanism of phytoplankton bloom forming, we investigated the relationship between several species and water quality factors using long-term monitoring datasets from 1996 to 2003. The seven sites at this study were classified into four groups by phytoplankton species or water quality datasets and the species for phytoplankton bloom forming seems to be mainly influenced by the water quality or surrounding water conditions. E. gymnastica and P. minimum were observed for the longest time period from April to September, and C. polykrikoides shortest time period from summer to autumn. E. gymnastica was observed across the widest temperature range (14–27ºC), and C. polykrikoides narrowest temperature range (20–28ºC). Chaetoceros spp. was observed over the narrowest salinity range (22–33 ppt), and E. gymnastica, P. minimum, H. akashiwo wide salinity range (14–34 ppt). The main reasons for the formation of Chaetoceros spp. and S. costatum blooms seems to be fresh water input through forest and fields by heavy rainfall events. Thalassiosira spp. seems to grow well in conditions of fresh water input and/or in eutrophicated areas with salinities >20 ppt and water temperatures >17ºC. C. furca seems to grow well in sea areas that are affected by inflows of domestic and industrial wastewater and by inflows of freshwater with domestic and industrial wastewater, rather than only freshwater input, after May when water temperatures are higher than 18ºC. E. gymnastica, H. akashiwo, P. minimum, and P. triestinum seem to grow well in eutrophicated sea areas where nutrient levels are high and where domestic and industrial wastewater flow are abundant. C. polykrikoides blooms seem to be due to suitable seawater input from off sea areas, and freshwater after heavy rainfall that has high nitrogen concentration.