Carbon, alkalinity and nutrient budgets on the East China Sea continental shelf

The western part of the Kuroshio Intermediate Water originates from the nutrient-rich South China Sea intermediate water which upwells onto the East China Sea (ECS) continental shelf and contributes a large amount of nutrients to the ECS. This contribution, especially for phosphorus, is far more than the inputs from the phosphorus-deficient Yangtze and Yellow Rivers. Mass balance calculations reveal that the net denitrification rate in the ECS shelf is 95 +/- 50 x 10(9) mol N yr(-1), which is more than the total riverine supply of nitrogen. The nutrient supply allows the ECS to produce 1030 +/- 310 x 10(9) moles dissolved organic carbon and 709 +/- 280 x 10(9) mol particulate organic carbon for a total of 1739 +/- 870 x 10(9) mol organic carbon per year, which translates to a new production rate of phytoplankton as 64 +/- 32 mg C m(-2) d(-1) or 15% of the average primary production rate. The downslope transport of modern particulate carbon is 2547 +/- 1250 x 10(9) mol yr(-1), of which 695 +/- 350 x 10(9) mol yr(-1) is organic. This value is only 12% of the offshore dissolved organic carbon transport of 5563 +/- 1700 x 10(9) mol yr(-1). The alkalinity budget, never attempted before, indicates that there is a substantial amount of alkalinity generation in the sediments (3.9 +/- 3.9 mmol m(-2) d(-1)) due to anaerobic respiration such as by iron and sulfate reductions.