Impacts of human activities on nutrient transports in the Huanghe (Yellow River) estuary

The impacts of anthropogenic activities on nutrient transport in the Huanghe/estuary were investigated using biogeochemical observations carried out during 2008–2009 to examine how nutrient change during a water–sediment regulation event. Nutrient concentrations in the Huanghe are characterized by relative high concentrations of nitrate and dissolved silicate but low phosphate and DOP levels and shows seasonal variations with very high DIN/PO43- ratios. The water–sediment regulation event resulted in high monthly average water discharge and sediment load occurring at least 2 months prior to before the event. The nutrient transport fluxes increased 8–30 times during that period. The regulation event has shifted the seasonal patterns of water and nutrient transport, which cannot only increase nutrient inputs to the coastal ecosystem but can also result in nutrient imbalance, affecting phytoplankton production and composition.