Inventory of nutrient compounds in the Yellow Sea

Nutrient species were analyzed from samples collected in the Yellow Sea in May 1998, including NO₃^-, NO₂^-, NH₄⁺, PO₄^3-, SiO₃ ^2-, dissolved organic nitrogen (DON), particulate nitrogen, dissolved organic phosphorus (DOP), particulate phosphorus, etc. The exchange fluxes of nutrients across the sediment/water interface were determined by incubation of sediment on board the ship. The concentrations of N, P and Si compounds were high in coastal areas of the Yellow Sea, reflecting the effects of the Changjiang effluent plume, surface runoff in the west and east coasts and the circulation in the Yellow Sea. The high proportions of DON and DOP should be considered in models of nutrients cycling, which could help to explain observations of nutrient limitation in ecosystems of the Yellow Sea. The vertical distribution of N, P and Si compounds in the water column showed stratification feature. Simple box model was used to estimate the water-mass balance and nutrient budgets for the Yellow Sea. The data suggested that water turn-over time is about 2.2 years. Nutrient budgets demonstrated that net sink of NO₃^-, NH₄⁺ and SiO ₃^2- can be mainly from water column into bottom sediments and/or transform to other forms of nitrogen (e.g. particulate pool and gas species). A net source of PO₄^3- is estimated to be 75% of inputs from external sources in the Yellow Sea.