Occurrence characteristics of harmful and non-harmful algal species related to coastal environments in the southern sea of Korea

Abstract

Because the phytoplankton community and blooms are regulated by various environmental factors, it is difficult to define the cause and occurrence of the phenomenon of harmful algal blooms (HABs). This study evaluated the phytoplankton community and occurrence characteristic of HAB species related to coastal environments in South Korea, 2016. In summer, because of strong upwelling event, the surface sweater temperature around Geoje Island was abnormally low (17°C), and an unusual high temperature (29°C) and low salinity (29psu) were measured in offshore area. Diatoms and dinoflagellates showed contrasting occurrences during the survey period. Diatoms were dominant in the inshore area, whereas dinoflagellates occurred in the offshore area. The phytoplankton-community structures were established depending on different hydro-oceanographic characteristics. In statistical analysis, HABs of dinoflagellate Karenia appeared in upwelling areas with a high nutritional content, whereas Gymnodinium, Gyrodinium and Prorocentrum appeared in areas of low nutrients in June, and HAB species showed an equivalent tendency to appear at high water temperature and low saline level in August. Our results indicated that hydro-oceanographic events such as river discharge, current and upwelling play important roles in determining the phytoplankton community and potential occurrence characteristics of HABs in the coastal environment of South Korea.