Program     Carbon Cycle in the South China Sea: Budget, Controls and Global Implications       Poster Nutrient transport and dynamics in the South China Sea: A modeling study P-SPS3-10 Zhongming Lu* , Hong Kong University of Science and Technology Jianping Gan, Hong Kong University of Science and Technology Minhan Dai, Xiamen University Xiaozheng Zhao, Hong Kong University of Science and Technology Presenter Email: luzm@ust.hk We investigated nutrient transport and dynamics in the South China Sea (SCS) using the three-dimensional China Sea Multiscale Ocean Modeling System (CMOMS) coupled with a nitrogen-phosphorus-phytoplankton-zooplankton-detritus (NPPZD) ecosystem model. The model was validated by both field and remote sensing observational data. We reveal that the lateral and vertical fluxes associated with three-dimensional ocean circulation, together with the biogeochemical processes, shape the spatiotemporal characteristics of nutrients in both the shelf and basin regions of the SCS. There exists a unique layered distribution of nutrients that increasing from north to south of the upper layer and an opposite condition of the middle and deep layers. The organic forms of nutrients contribute importantly to the overall nutrient budget in the SCS, as nutrients exchange with the adjacent oceans in the upper layer through shallow straits. The nutrients in the euphotic zone of the N-limited oligotrophic SCS basin is mainly derived from the upward flux and remineralization, but it is diluted by influx through the Luzon Strait and consumed by biological production. Influx/outflux to the basin and subsequent vertical flux act as sources/sinks in the middle and deep layers. Remineralization contributes more importantly to PO4 than does NO3 in both the shelf and the basin due to its higher recycling rate. NO3 in the N and P co-limited shelf water comes from river plume and coastal upwelling, but it is consumed by biological production and downward flux, while PO4 mainly comes from remineralization and upward flux due to the strong downward increasing gradient.