Post-Typhoon Reorganization of Estuarine Plankton Communities in Matsu Archipelago

The Matsu Archipelago is a coastal marine system affected by freshwater discharge from the Minjiang River. Enhanced freshwater input from typhoons and high-intensity rainfall events can further alter local plankton communities. In this study, we divided the sampling period into (1) a freshwater-disturbed period characterized by reduced salinity and (2) a subsequent stable period, when the system began to recover. During the “Disturbed period”, we observed a brief occurrence of Noctiluca scintillans , although its abundance remained well below bloom levels (peaked only in 4.69 cells L⁻¹). After rainfall ceased, diatom abundance increased exponentially, driven primarily by Chaetoceros , which peaked at 3.7 × 10⁷ cells L⁻¹ and was followed by a rapid rise in copepod abundance (5.3 ind L⁻¹). In contrast, dinoflagellate abundance did not differ significantly between the two periods; instead, dinoflagellate bloom (3.97 × 10 ⁴ cells L⁻¹) occurred during the short transitional phase between them. Overall, this study suggests that event-scale freshwater inputs structure plankton dynamics in this coastal system, triggering a succession from the initial appearance of Noctiluca scintillans coincident with rainfall, through a brief dinoflagellate bloom during the transitional phase, to rapid exponential increases in diatom abundance during the subsequent “Stable period”, followed by a marked rise in copepods in the final day of the survey.