Spatiotemporal Response and Evaluation of Composite Marine Carrying Capacity Driven by Various Factors

This study quantifies the sustainable development thresholds of marine ecosystems under high-intensity human development by establishing a composite evaluation framework based on the Pressure–State–Response (PSR) model. Taking the Nantong sea area as a typical study region, this research indicates that prior to large-scale development (2006–2010), the comprehensive carrying capacity was higher in the northern region than in the south. The lowest capacity was observed near the Yangtze River Estuary, while the Subei Radial Sand Ridges in the north exhibited the highest capacity. Following the period of intensive coastal development (2016–2020), a significant decline in composite marine carrying capacity occurred in the northern radial sand ridge area, whereas the central waters remained stable. The nearshore areas in the south exhibited the poorest capacity. Despite a substantial increase in anthropogenic pressure, the overall decline of the sea area’s composite marine carrying capacity remains within an acceptable range, with all levels categorized as “Near Carrying Capacity” or above. Quantitative assessment of marine environmental carrying capacity and marine ecological carrying capacity provides an effective pathway for monitoring the specific status of the marine environment and determining whether critical thresholds have been reached under high-intensity human development scenarios.