Phytoplankton and Primary Production in the Japan Sea

Abstract

The Japan Sea is a marginal sea surrounded by the Japanese archipelago, Korea Peninsula, Sakhalin Island, mainland China and Russian landmasses which isolate it from the East China Sea, Pacific Ocean, and Okhotsk Sea. In this chapter, studies of phytoplankton and primary production in the Japan Sea using ocean colour satellite data have been summarized. Satellite chlorophyll-a (Chl-a) concentrations were generally well correlated with in situ Chl-a, except in low chlorophyll-a regions within the central region of the Japan Sea, where satellite estimates were higher. A marked seasonality in Chl-a was observed in association with spring and fall blooms over large areas of Japan Sea, with the spring bloom commencing around the subpolar front in the south moving northwards. Overall, interannual variations in Chl-a, appeared to be related to large scale global climate variations. Despite observations of increasing trends in Chl-a, reports of decreases in primary production require that we continue to better understand the role of physical forcing factors in particular, how mesoscale eddies and typhoons that are unique to this region, regulate primary production and phytoplankton biomass distribution. This review also draws attention to the lack of ocean colour algorithms for discriminating phytoplankton functional groups from space. The availability of satellite derived information on phytoplankton functional groups is essential for ocean biogeochemical and fisheries research. This study also emphasizes the need for more bio-optical measurements and algorithm development efforts to fill this gap.