The surface nutrients in China's coastal waters in the winter of 2025

Nutrients are the material basis of marine ecosystems, and understanding their levels and structures is of great significance for fully understanding marine ecosystems. Based on a survey of surface water in China's coastal waters in January 2025, this study explored the spatial heterogeneity and controlling factors of nutrient distribution in different areas of China's coastal waters. The results showed that there are significant regional variations in nutrient levels and structures, with the East China Sea exhibiting the highest concentrations of NO₃-N, PO₄-P, and SiO₃-Si, while the South China Sea showing the lowest levels and a distinct nitrogen-deficient signature. Contrastingly, the Bohai Sea was identified as a phosphorus-deficient signature, reflected by elevated DIN:PO₄-P ratios. The observed nutrient distributions and structures were shaped by various factors. The South China Sea exhibited typical oceanic characteristics. The southeastern East China Sea was significantly affected by the Taiwan Warm Curren. As a semi-enclosed bay, the Bohai Sea had limited water exchange, resulting in higher nutrient levels. River input played a significant role in all the studied sea areas, markedly increasing nutrient concentrations. These insights underscored the complex biogeochemical processes governing nutrient dynamics and provide a scientific foundation for assessing nutrient limitations and eutrophication risks in diverse coastal marine environments of China.