River export of nutrients are disturbed by multiple anthropogenic activities in the watershed. Understanding the river export of nutrients ratio and its drivers are important in mitigating the degradation of coastal ecosystems. This study aimed to investigate the temporal pattern of river export of nutrient ratio by the Yangtze over the last decade and identify the dominant anthropogenic drivers. Our results showed that the ratio of nitrogen (N) to phosphorus (P) in river export increased from 1000 to 1200 from 2012 to 2021. This increase can be attributed that river export of total P (TP) by the Yangtze decreased by 80%, while river N export remained stable. Between 2012 to 2021, river export of TP in most upstream tributaries of the Yangtze showed a decreasing trend, primarily due to the increasing number of river dams. However, decline in river TP export by upstream sub-basins had a limited impact on the increase TN:TP ratio of river export to the coastal water by the Yangtze, due to retention effect of the Three Gorges Dam. Instead, Middle stream and Delta contributed the most to the increase in the river export of TN:TP ratio to the coastal waters. The improvement of wastewater collection and treatment were found to be important drivers. This study calls for more attention to the mismatch of N to P in river export caused by anthropogenic activities.
 

sub-basin, river dams, retention, modeling, coastal water