Interannual dynamics and assembly mechanisms of mycoplankton community amid climate disturbances in the Yellow Sea

Understanding the mechanisms underlying marine fungal community turnover is critical to predicting community responses to climate disturbances. Yet, the interannual stability of mycoplankton community composition, structure, and network organization in the Yellow Sea (YS) remains poorly understood. Here, we investigated fungal community interannual dynamics from 2017 to 2022 within the Yellow Sea Cold Water Mass (YSCWM) and adjacent surface waters in northern (NYS) and southern (SYS) YS during summer. Seawater samples from different depths of the three regions (YSCWM, NYS, and SYS) of the YS were analyzed based on fungal ITS2 amplicon sequencing. Community composition and structure were highly sensitive to environmental disturbances, with sharp declines in diversity and network connectivity. Notably, the record-breaking marine heatwave (2018), local cyclones (2020), and typhoon Lekima (2019) likely decimated dominant fungal taxa and significantly decreased diversity. This environmental fluctuation period coincided with the proliferation of Aspergillus , Alternaria , Cladosporium , Rhodotorula , Acremonium , Malassezia , and Fusarium . Dispersal limitation and drift were the main driving processes of community turnover, with temperature and phosphate as key drivers within the YSCWM and outside at SYS. An increase in seawater temperature and phosphate concentration might lead to a significant decline in fungal diversity. The YSCWM emerged as a critical reservoir of fungal biodiversity, particularly minor taxa that appear to persist under stress. Our findings shed light on the temporal dynamics of fungal communities in the YS, underscoring their susceptibility to drastic oceanic events. Moreover, they highlight the potential role of the YSCWM in ecosystem sustainability under changing climate conditions.