Variability in the primary production in the East Sea
Why and how the fisheries resources fluctuate have been among the central questions in the marine ecology. Despite the rapid development in the observation technology and accumulation of research outputs, we still fall short of full answers. For example, while we acknowledge the fact that there have been abrupt changes in the East Sea ecosystem after 1976 regime shift, we still do not know the details of the process. To understand such process, we should trace from the changes in the physical forcing and lower trophic level. There are three pathways through which the changes in the lower trophic level can be transferred to higher level: 1) changes in the total throughput in the primary production, 2) timing in the seasonal cycles in the production, 3) changes in the size structure in the producer community. The time-series of synoptic images provided by the first ocean color sensor, CZCS (Coastal Zone Color Scanner) enabled us to see the seasonal changes in the basin-scale surface chlorophyll concentration in ecologically-reasonable spatial resolution. Yoo and Kim (2003), using CZCS data, estimated the annual gross primary production in the East Sea to be 240 mg C m-2 yr-1, which is higher than previous estimates based on shipboard measurements. The uncertainty arises from the errors in the estimation of chlorophyll concentration and photosynthetic parameters, and further improvement of algorithms using field data is required.