Long-term ecological health assessment of the yellow river estuary (2003−2022) using an EQR-standardized PSR framework with entropy weighting

Estuaries are highly valuable but increasingly engineered ecosystems, where apparent recovery may reflect direct management inputs rather than autonomous ecological improvement. Existing PSR- and DPSIR-type assessments rarely separate these signals, potentially inflating recovery diagnoses. Therefore, we developed a management-adjusted Pressure-State-Response and Ecological Quality Ratio (PSR-EQR) framework for the Yellow River Estuary (YRE) using a continuous 2003–2022 monitoring record. The 24-indicator framework partitions the Response domain into management-response indicators, such as ecological water supplementation and wetland-protection effort, and biotic-response indicators, such as fish early-life-stage and benthic-community metrics. Each indicator was transformed to a 0–1 EQR using cost-, benefit-, or optimum-type functions against auditable benchmarks, weighted with the Entropy Weight Method, and examined with exploratory PCA after correlation-guided block aggregation. The results showed that the full PSR trajectory was inverted-N-shaped, declining from 0.685 in 2003 to 0.428 in 2016 and rebounding to 0.715 in 2022. The 2016 minimum coincided with severe summer hypoxia (DO = 2.1 mg/L) and opportunistic benthic dominance. After 2019, State and biotic-response indicators improved, but management-response indicators reached benchmark conditions earlier. The ecological-core diagnosis therefore indicated slower intrinsic recovery than the full score, highlighting continuing management dependence. The framework provides a transferable approach for highly engineered estuaries by separating ecological condition from direct management inputs while preserving PSR-EQR comparability.