Increasing input of anthropogenic nitrogen drives the East China and Yellow Seas to Phosphorus limitation

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 P-limited. In 1980s, P limited area was small and mostly confined to the coastal areas near the mouth of Changjiang River, whereas the rest of East China and Yellow Seas remained severely deficit in N relative to P. After 1990s onward, the P-limited waters have rapidly expanded to the downstream of the Changjiang River, including the southern and eastern coastal waters of Korea. The areas located outside of downstream of Changjiang River remains still being N-limited relative to P but the magnitude of N deficiency has been less severe over time. Our results provide unique observational evidence pointing to a nutrient regime shift (i.e. N limitation transiting to P limitation), largely driven by anthropogenic N inputs, in extensive areas of East China and Yellow Seas in the vicinity of the largest source of anthropogenic N (northeastern Asian continent).