An observation of primary production enhanced by coastal upwelling in the southwest East/Japan Sea

Abstract

Abstract Coastal upwelling (CU) is an important process that causes changes in physical and chemical properties, resulting in variation of biological processes in a coastal area. In the southwestern part of the East/Japan Sea (SWES), CU has been alleged as one of the mechanisms responsible for higher net primary production (NPP) than the rest of the East/Japan Sea. We provide, for the first time, high spatial resolution underway observations of sea surface temperature, salinity, chlorophyll-a fluorescence and Δ(O2/Ar), revealing the physical and biological characteristics of the upwelled waters in the SWES. The cold, upwelled waters retained high fluorescence and Δ(O2/Ar), consistent with enhanced phytoplankton biomass and biological O2 production by CU. The net community production (NCP) in the ambient and upwelled waters were 33 ± 19 and 77 ± 41 mmol O2 m−2 d−1, respectively. The latter should be considered as a lower bound, containing a significant fraction of low O2 waters from subsurface. Satellite observation indicated that NPP in the upwelled waters were higher than the ambient waters by 51%. This implies that up to half of higher NPP in the SWES than the rest of the East/Japan Sea can be ascribed to CU events.