Salinity Gradients Determine the Resilience of Estuarine Microbial Ecosystems to Extreme Weather Events

Extreme weather events, exacerbated by anthropogenic climate change, exert increasing pressure on coastal ecosystems and the biogeochemical services they sustain. However, the mechanisms governing the full cycle of ecosystem stability — encompassing both resistance to and resilience from large-scale disturbances — remain inadequately understood. Here, by tracking bacterioplankton community dynamics across a subtropical estuary through a complete disturbance-recovery cycle following Typhoon Haikui, we demonstrate that the pre-existing salinity gradient serves as a master regulator of ecosystem stability. We observed fundamentally divergent ecological trajectories contingent on baseline salinity: low-salinity riverine communities experienced a prolonged state shift, characterized by the proliferation of opportunistic r-strategists and a collapse in co-occurrence network complexity, indicative of stochastic community assembly. In contrast, high-salinity bay communities exhibited robust resistance, maintaining a K-strategist-dominated structure through deterministic environmental filtering. This stability was underpinned by the activation of a resilient rare biosphere, which fortified network connectivity and provided functional redundancy. A meta-analysis of seven additional storm events corroborates the universality of this pattern. Our findings reveal a significant temporal decoupling, whereby biological recovery substantially lags behind the normalization of the physicochemical environment, establishing a predictive framework for identifying resilience anchors and vulnerability hotspots in coastal zones.