Decadal Changes of Phytoplankton Chlorophyll-a
in the East Sea/Sea of Japan¹

S. H. Lee^a*, S. Son^b, H.-U. Dahms^c, J. W. Park^a, J. -H. Lim^d, J.-H. Noh^e, J.-I. Kwon^e, H. T. Joo^a,
J. Y. Jeong^e, and C.-K. Kang^f

^a Department of Oceanography, Pusan National University, Pusan, South Korea

^b CIRA, Colorado State University, Fort Collins, CO, USA

^c Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University and Department of Marine
Biotechnology and Resources, National Sun Yat-sen University, Taiwan

^d Marine Environmental Research Division, National Fisheries Research Development Institute, Busan, Korea

^e Korea Institute of Science and Technology, Ansan, South Korea

^f School of Environmental Science & Engineering, Gwangju Institute of Science & Technology, Gwangju, South Korea

*e-mail: sanglee@pusan.ac.kr

Received October 18, 2012; in final form, July 9, 2014

Abstract—The East Sea has very dynamic environmental conditions with respect to its physical phenomena
and biological characteristics. In order to detect any longterm change in patterns of phytoplankton biomass and
a longterm trend in phytoplankton spring bloom characteristics in the East Sea, recent decade chlorophyll-a data
were obtained for the East Sea from NASA SeaWiFS and MODIS. We found that the average Chl-a concentra-
tion from 2008–2011 was rather higher than that from 1998–2001 in the East Sea, especially along the coastal
areas and the sub-polar fronts. Distinctively, the patterns of the Chl-a concentration such as duration and inten-
sity of the phytoplankton spring bloom were significantly different between the periods from 2008–2011 and
1998–2001. During the observation period, there were no distinct trends in environmental conditions in the East
Sea. Several potential mechanisms for these changes are suggested for further intensive field studies. First, a
recent increase in anticyclonic eddies could seed an early spring bloom of the phytoplankton. An increase of
sea surface temperature in winter could also cause an earlier stratification leading to an earlier start of the
bloom. Furthermore, a change of light regime might take place in the euphotic zone in the East Sea.

DOI: 10.1134/S0001437014060058

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