Phytoplankton dynamics driven by vertical nutrient fluxes during the springinter-monsoon period in the northeastern South China Sea

[摘要] A field survey from the coastal ocean zones to the offshore pelagic zones ofthe northeastern South China Sea (nSCS) was conducted during theinter-monsoon period of May 2014 when the region was characterized byprevailing low-nutrient conditions. Comprehensive field measurements weremade for not only hydrographic and biogeochemical properties but alsophytoplankton growth and microzooplankton grazing rates. We also performedestimations of the vertical turbulent diffusivity and diffusive nutrientfluxes using a Thorpe-scale method and the upwelling nutrient fluxes byEkman pumping using satellite-derived wind stress curl. Our resultsindicated a positive correlation between the integrated phytoplanktonchlorophyll a and vertical nutrient fluxes in the offshore region of the nSCSduring the study period. We generally found an increasing role of turbulentdiffusion but a decreasing role of curl-driven upwelling in verticaltransport of nutrients from the coastal ocean zones to the offshore pelagiczones. Elevated nutrient fluxes near Dongsha Islands supported high newproduction leading to net growth of the phytoplankton community, whereas thelow fluxes near the southwest of Taiwan had resulted in a negative net communitygrowth leading to decline of a surface phytoplankton bloom. Overall,phytoplankton dynamics in the large part of the nSCS could be largely drivenby vertical nutrient fluxes including turbulent diffusion and curl-drivenupwelling during the spring inter-monsoon period.

[学科分类] 地球化学与岩石