Abstract
Estuarine ecosystems worldwide are increasingly threatened by pollution and intensifying human activities, yet integrated approaches that reconcile conservation with sustainable resource use remain underdeveloped. This study addresses this gap by developing a novel framework to identify priority conservation areas in heavily polluted, multi-use estuaries. Focusing on the Yangtze River Estuary, one of the world's most impacted marine systems, we integrated a Marine Use Conflict-Synergy Assessment (MCSA) with a Cumulative Impact Assessment (CIA) targeting aquatic species. Here, conflict was defined as the spatial-functional incompatibility among human uses, while synergy reflected the efficiency gains from coordinated multi-use. Our results showed that pollution, shipping, and offshore infrastructure constituted the dominant pressures in the region. Approximately 87.94 % of areas with extremely high cumulative impacts overlapped with zones of high marine-use synergy, particularly in major shipping channels. Areas of pronounced use conflict were concentrated near the river mouth and within offshore wind-farm clusters. Based on a two-dimensional gradient of cumulative impact and conflict-synergy levels, five distinct conservation target types were delineated, which informed the design of an optimized marine spatial planning scheme for priority conservation. The proposed framework advances existing methodologies by operationally coupling cumulative impact and use-interaction assessments, providing a transferable approach for spatial planning adjustment in polluted, multi-stress estuaries worldwide. It thus contributes to both marine pollution science and evidence-based coastal management practice.