Chang Kyu Lee, Chang Su Jung, Wol Ae Lim, Sam-Geun Lee and Hak Gyoon Kim
Harmful Algal Blooms Research Division, National Fisheries Research and Development Institute, Busan 619-902, Rep. of Korea

Abstract

Harmful algae, Cochlodinium polykrikoides has damaged to fisheries organisms by making massive blooms mainly in the South Sea during the higher water temperature season since 1995 in Korea. We studied the quantitative analysis of swimming cells and the hydrographic characteristics for three years, particularly, during the periods from the first appearance of swimming cells to the outbreaks in the South Sea of Korea.
One or two chained young swimming cells of the species were initially observed from the samples two to six weeks ago before making blooms in the South Sea of Korea. However, it took only one or two weeks until making blooms at the cell concentration of 50 cells/L in an average. Although there were no any significant differences in the date for the first appearance of swimming cells depending on the location in the South Sea, the elapsed time to blooms was the shortest near Narodo, indicating that the coastal area near Narodo was the most environmentally attractive place for the growth of the species.

The quantity of zooplankton for warm current indicate species was far more at the offshore between Geomoondo and Jejudo, about 25-75 miles off from Narodo, than at the inshore between Kwangdo and Narodo. Also, the hydrographic data such as temperature, transparency, nutrient concentration, etc gave us the context that the area near Kwangdo and Geomoondo was a frontal area where there was active mixing between inshore and offshore water. More ever, the quantity of young swimming cells near Kwangdo and Geomoondo at the initial appearance time outnumbered that of other area. Therefore, these kind of environmental characteristics at this area was assumed to lead the species to grow better than other area. In addition, the time when thermocline begins and what the strength of cold water is, annually concurring near Narodo, might affect deeply on the elapsed date to the beginning and scale of blooms for the species near Narodo.