Spatially Explicit Inventory of Sources of Nitrogen Inputs to the Yellow Sea, East China Sea, and South China Sea for the Period 1970–2010

Serious eutrophication of China’s coastal seas

Symptoms of eutrophication (including biodiversity loss, harmful algal blooms, and hypoxia) are an increasing problem in Chinese seas. Nutrient enrichment is primarily caused by accelerated human activities that cause nutrient pollution of the aquatic environment.

Long-term changes of nutrient loading

In this study, the Integrated Model to Assess the Global Environment–Global Nutrient Model (IMAGE‐GNM) was used to estimate nitrogen inputs from river discharge, submarine fresh groundwater discharge, and mariculture, and TM5‐FAst Scenario Screening Tool (TM5‐FASST) for atmospheric nitrogen deposition to the three Large Marine Ecosystems (LMEs, i.e., Yellow Sea/Bohai Sea, YS/BS; East China Sea, ECS; South China Sea, SCS) bordered by China for the period 1970–2010.

Agriculture and aquaculture are dominant

The total nitrogen inputs to YS/BS (1.0 to 4.1 Tg/year), ECS (1.3 to 5.5 Tg/year), and SCS (2.1 to 5.8 Tg/year) increased rapidly during 1970–2010. River export is dominated by agriculture; nitrogen inputs from atmospheric deposition and mariculture have been increasing rapidly in recent years. Considering only the coastal zone of the three LMEs, our results show that the total nitrogen inputs are strongly concentrated spatially in areas close to river mouths and those confined regions with mariculture production. To sustain food production and economic growth in the coming decades, nitrogen inputs may increase further, depending on future eutrophication mitigation policies.