研究期間：10108~10207;This is Subproject 19 of the ECOBEST-I integrated project. The objectives are: (1) Understanding of the processes crucial to the biogeochemical cycles and the ecosystem of the western North Pacific (west-Pac) Marginal Seas, mainly, the East China Sea (ECS) and South China Sea (SCS), as driven by the Kuroshio, river runoffs and wind forcing under a changing world; (2) Assessment of the biogeochemical and ecosystem responses to natural fluctuations and anthropogenic alterations of forcing functions, especially changes in the hydrological cycle and anthropogenic alteration of the nutrient cycles; and (3) Investigation of mechanisms responsible for any discernible changes in the biogeochemical system and/or the ecosystem in the future with special focus on changes in biological productivity. We will rely on modeling approaches as well as isotopic techniques for the investigation. The major issues in the west-Pac marginal seas this subproject will address include the impacts of changing hydrological cycle, anthropogenically altered biogeochemical cycles, and changes in tropical cyclone occurrences. Modeling approaches will be used to understand processes involved in the influences on the marginal sea biogeochemistry due to flooding and wind-driven mixing associated with tropical cyclones; it will also be applied to delineate the changes in biogeochemical conditions of the marginal seas, such as algal bloom, hypoxia and carbon chemistry (including shelf pump capacity and acidification), induced by anthropogenic nutrient loads in river discharges. This Subproject will closely collaborate with Subprojects 17 and 18 to improve the circulation model for the Kuroshio, East China Sea and South China Sea. The ecosystem structure of the current module is rather simple with limited compartments involving only carbon and nitrogen. Since the biological activities in the west-Pac marginal seas are limited not just by nitrogen but also by phosphorus or silicon, it will be necessary to include other limiting nutrients in the module. As the carbon pathways have been included in the biogeochemical module to investigate the seasonal variation of the air-sea carbon dioxide fluxes, it can be used to investigate the changes in pH in the future. Moreover, oxygen needs be included in the model so as to explore the hypoxic conditions in the marginal seas. Nitrogen isotopic composition will be used to trace nitrogenous nutrients of different origins in the marginal seas.
