Analysis of spatial heterogeneity evolution in Dashentang oyster reefs: anthropogenic activities and environmental...

Dashentang oyster reefs (Tianjin, China) experienced severe degradation and exhibited pronounced spatial heterogeneity following restoration. Based on in-situ observations and numerical simulations, this study examined the spatiotemporal evolution of oyster reefs over the past two decades and identified the dominant factors. Results showed that anthropogenic activities dominated reef evolution. Before 2005, overfishing caused large-scale reef degradation. Between 2007 and 2012, coastal engineering construction and associated changes in hydrodynamics and sediment transport led to southern reef loss and suppressed recovery, resulting in spatial heterogeneity. Since 2012, government conservation measures and shifts in fishing practices by fishermen have promoted reef development in the northern area, while coastal engineering constrains have continued to limit southern reef, further intensifying spatial heterogeneity. Notably, driven by economic benefits, fishermen voluntarily adopted ground cage traps, which limited trawling and reduced predation pressure, facilitating reef recovery. Water quality factors were not the limiting factors before 2020. However, climate-driven water quality changes and extreme events may pose potential risks and warrant policy attention.