The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Many large estuaries are threatened by intensifying hypoxia. However, due to the limited duration of available observations,uncertaintiespersist regardingthelevelofcontemporaryhypoxiaintensityina longer-term context and the relative contributions of climate versus human factors. Here we present sediment records for the hypoxia intensity and associated environmental parameters in the Yangtze Estuary over the past three centuries. The results show that the hypoxiaintensity has been increasing during the last half century due to anthropogenic eutrophication, but the current hypoxia condition is not as severe as some preindustrial periods due to weaker stratification in the water column. Our f indings suggest that if anthropogenic and climatic forcing coincide in the foreseeable future, the hypoxia intensity of the Yangtze Estuary may reach unprecedented levels.