Algae. 1998; 13(1): 123-133.

Long-term Variation of Phytoplankton Biomass and Implication in the East and the South Sea, Korea

Jong-Gyu Park, Jae-Hyung Shim, Joon-Baek Lee

Institute of Environmental Research, Inje University, Department of Oceanography, Seoul National University, Department of Oceanography, Cheju National University

For the study of long-term variation of phytoplankton biomass,11,729 Secchi depth observations were analysed, which were obtained from the KODC (Korean Oceanographic Data Center) during the period from 1961 to 1990. Chlorophyll a concentrations in the southern East Sea were well correlated with Secchi depth transparencies (r super(2)=0.64, log transformed )n and showed characteristics of Case I waters in open ocean. F-test results indicated that the transparency had been changed at about 15% of the total area in the East and the South Sea since 1961. The biomass inferred from transparency has not been changed in the southern East Sea over the past 30 years, but on the observation line between Pusan and Tsusima island it has gradually increased and average annual increase of chlorophyll a was over 0.018 mg m super(-3). Considering the effect of nonbiological material on Secchi depth observations in coastal waters, it is possible that these variations may occur all over the neighboring coastal waters around Korea, which in turn will have some contributions to the removal of CO sub(2) in atmosphere.

Keywords : long-term variation, phytoplankton biomass, Secchi depth, transparency