Future responses of nutrients in the Yellow Sea and East China seas to climate change and riverine inputs

Nutrients are key regulators of marine primary productivity and ecosystem structure in shelf seas. Investigating future changes in nutrients to climate change and riverine inputs is essential for understanding the response of shelf sea ecosystems and for developing effective marine pollution mitigation strategies. In this study, a 3-dimension biophysical-geochemical coupled model was used to study the spatiotemporal distribution of dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) in the 2010s and the 2050s under the high-emission scenario in the Yellow and East China Seas. Results indicate that in the 2010s, nutrient concentrations generally decrease from inshore to offshore in the surface waters. Seasonally, nutrient concentrations peak in winter. Under the high-emission scenario, the overall spatial distribution of nutrients is largely consistent with the present, with high-DIN changes primarily detected in the Yangtze River estuary-Hangzhou Bay and adjacent waters, while high-DIP changes are mainly found in the western Yellow Sea. Sensitivity experiments further quantify the relative contributions of climate change and human activities to nutrient variations. Results show that elevated riverine inputs mainly affect nearshore waters, whereas climate change exerts a stronger influence on offshore regions.