Post-typhoon reorganization of estuarine plankton communities in matsu archipelago

Abstract The Matsu Archipelago is a coastal marine system heavily influenced by freshwater discharge from the Minjiang River, which is often intensified by episodic typhoons. To understand how such extreme weather event restructure estuarine plankton communities, we conducted high-frequency day–night sampling for nine consecutive days at Nangan Island, Matsu Archipelago, following Typhoon Danas in July 2025. Initial post-typhoon conditions were characterized by low salinity (~ 24.5 PSU) followed by subsequent sharp rebound and stabilization (~ 32 PSU), thus we defined two distinct phases: a rain-affected “Disturbed period” and a post-rain “Stable period”. During the early Disturbed period, the pioneer taxon Noctiluca scintillans briefly appeared, followed by a transient bloom of the opportunistic dinoflagellate Alexandrium that coincided with the rapid salinity surge between the two periods. After the system transitioned into the Stable period, an exponential diatom bloom dominated by Chaetoceros developed, triggering a rapid increase in copepod abundance. These results demonstrate a rainfall-driven succession from disturbance-associated pioneer and opportunistic assemblages to a stabilized, diatom-dominated community and subsequent grazer response. This pattern reflects recovery toward a typical nutrient-rich and highly productive estuarine ecosystem. By resolving these short-lived transitions, our study highlights the critical role of high-frequency, event-scale observations in capturing transient ecological processes and advancing our understanding of trophic dynamics and ecosystem responses in river-influenced coastal systems.