Response of Nutrients and Primary Production over the Shelf in the East China Sea to the Reduction of Oceanic Nutrient Supply

A three-dimensional coupled biophysical model was used to examine the response of oceanic nutrients and primary production over the continental shelf to reduction of the oceanic nutrient supply in the East China Sea (ECS). The model consisted of two parts: the hydrodynamic module was based on a nested model with a horizontal resolution of 1/18 degree, whereas the biological module was a low trophic level ecosystem model including two types of phytoplankton, three elements of nutrients, and biogenic organic material. After completing a control calculation designed to reproduce the climatological conditions of this low trophic level ecosystem, the concentrations of nutrients in the Kuroshio water were artificially reduced by 30%. A reduction in nutrients over the shelf was then observed in the bottom layer from spring to summer, and in the surface layer from autumn to winter. A reduction in primary production over the shelf was found not only in the surface layer in winter but also in the subsurface layer over the shelf from spring to autumn.