南海北部陆架区浮游植物生产力对珠江冲淡水盐度锋面的响应

Primary production plays a major role in marine biological pump and can be divided into regenerated production and new production according to its nitrogen source and form, and new production is a measure of the efficiency of the biological pump. The utilization of phytoplankton on different forms nitrogen has a preference, and the variation of uptake rate of different forms nitrogen might be lead to the change of biological pump efficiency. Salinity front forms by the interaction between riverine water and the higher salinity shelf waters and has a sharp salinity gradient, nutrient transportation will be hindered and lead to high levels of primary production and biological activity. Our proposal focuses on the response of nutrient structure, phytoplankton, zooplankton grazing, uptake rate of different nitrogen forms and productivity to the Pearl River salinity front. The field investigations will be conducted across salinity front to examine zooplankton grazing, nitrate uptake rate, ammonium uptake rate along a transect across salinity front in the northern South China Sea during summer and winter. The research output will identify in influence of phosphorus limitation on phytoplankton uptake rate of different nitrogen form, to assess the impact of salinity front on phytoplankton productivity, and to improve our understanding of the effect of salinity front on marine ecosystem.

初级生产力在海洋生物泵中扮演主要驱动力的作用，根据其氮源和形态又可分为再生生产力和新生产力，新生产力则成为生物泵效率的一个量度。浮游植物自身对不同形态氮的吸收和利用具有一定偏好，其对不同形态氮的吸收速率变化必然引起生物泵效率的改变。盐度锋面是河口冲淡水在大陆架近岸产生的低盐水与高盐海水的急剧过渡带，对营养物质的输送起到阻碍作用，因而在锋面位置往往出现浮游生物生物量及生产力高值区。本项目计划以南海北部为研究区域，跨珠江冲淡水盐度锋面开展受控培养实验，明确营养盐结构、浮游植物组成、浮游动物摄食率、不同氮源吸收速率和生产力跨盐度锋面的变化规律，验证冲淡水输入引起的磷限制对浮游植物吸收利用不同形态的氮是否有差异，期望从锋面对浮游植物吸收利用不同氮源的影响来阐明冲淡水盐度锋面对浮游植物生产力的调节机制。研究成果有望提升我们对冲淡水输入对跨锋区海洋生态系统结构和功能的影响的认识。