Influences of natural and anthropogenic processes on the nitrogen and phosphorus fluxes of the Yangtze Estuary, China

Nutrient flux to the sea through the estuary is important to the health of the sea. Combining natural processes with anthropogenic activities, we discuss the influence on the nitrogen and phosphorus fluxes to the Yangtze River basin, to the estuary and to the sea. The fluxes of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) to the estuary through the river/estuary interface are obviously higher than those to the sea through to the estuary/sea interface of the Yangtze estuary. The changes in nutrient fluxes through different interfaces are largely due to the estuarine hydrological and biogeochemical processes. Household, livestock and agricultural runoff are major sources of nitrogen from human activities, and household and livestock contribute to an increase in the anthropogenic phosphorus. The fluxes of DIN and DIP from economic activities account for about one-third of DIN and DIP fluxes to the sea through the Yangtze estuary.