Program

The continental shelf waters of East China Sea (ECS) is well-known as the most seriously influenced shelf marginal sea in China by human activities. Due to excessive input of terrestrial nutrients, especially from the Changjiang River discharge, this water is suffering from more and more serious coastal eutrophication and Harmful Algal Blooms (HABs) disaster in latest decades. However, in recent studies, it was argued that there might be alternative resources of nutrients, from where nutrients could be transported naturally to the HABs frequently occurred area. Therefore, it would be competitively attributable for ecological disasters with territorial input, either. This statement was further discussed within this research based on field investigations from the coast to -100m isobaths in the ECS and east waters off the Taiwan Island, 2014. It was indicated that there were some saline (S>34.6) waters (or we called it High Salinity Waters, HSW) at the bottom of the area along -100m isobaths, in which PO₄-P concentration could reach 1.06umol/L. Such value approached the highest concentration of PO₄-P in the surface close to the Changjiang River Estuary. Such water that was proved originating from Kuroshio Subsurface Water (KSSW), could be transported to the subsurface layer along -50m isobaths off the Zhejiang coast in spring. Furthermore, a hydrodynamic based box model was built to estimate the flux of N and P nutrients along such transportation path towards the coast. As a result, the flux of P could be 4 times over territorial inputs by such transportation synchronously. Consequently, P in ECS was influenced mainly by natural processes. Meanwhile, N in such waters was primarily discharged from territory, especially from the Changjiang river. As a whole, both anthropogenic impacts and natural influences ought to be equivalently important when considering the transportation of nutrients in the continental shelf waters of ECS.