Interannual nutrient dynamics in Korean coastal waters

The dynamics (interannual) of dissolved inorganic nutrient concentrations (dissolved inorganic nitrogen, DIN; dissolved inorganic phosphorus, DIP; and dissolved inorganic silicate, DSi) were investigated in inshore and offshore waters of Korea using time series data collected from 1994 to 2010. During this period the DIN concentration progressively decreased in most parts of the inshore areas, but markedly increased in offshore waters. In the inshore waters, where river-borne nutrients are a dominant source, the trend of decreasing DIN concentration reflected the trends of riverine DIN. Riverine sources are less important in the offshore waters, and the trends of increasing concentrations of DIN and DSi in the offshore waters reflected the trends of increase in atmospheric deposition and Asian dust, respectively. Inputs from submarine groundwater discharge and lateral current transport were also partly responsible for the changes in nutrient concentrations in the inshore and offshore waters, respectively. Our results indicate that the recent changes in nutrient concentrations in the inshore and the offshore waters of Korea are largely governed by changes in the relative contributions from riverine inputs and atmospheric deposition, which often have differing trends over time.