Impacts of Anthropogenic Nitrogen on Ocean Nitrogen System in the Yellow and East China Seas

Abstract

Increase in anthropogenic emissions of reactive nitrogen from China, Korea, and Japan, and its subsequent addition, via riverine input and atmospheric deposition, to the East China and Yellow Seas has led to an unprecedented increase in the nitrate (N) concentration of the upper ocean, without the proportional increase in phosphorous (P). The disproportional addition of anthropogenic N that persisting the past 4 decades has progressively driven the extensive regions of the East China and Yellow Seas from being N-limited to being Plimited. Our results provide unique observational evidence pointing to a nutrient regime changeover (i.e. N limitation to P limitation), largely driven by anthropogenic N inputs, in extensive areas of East China and Yellow Seas. The changeover in nutrient regime transformed the study area to the new condition in which the frequency of dinoflagellate bloom began to surpass over that of diatom bloom and dinoflagellate is known to better enable the acquisition of P (both inorganic and organic forms).