Abstract:[Background] Harmful algal blooms (HABs) in coastal waters can significantly change the composition of microbial community, thereby affecting the cycling of carbon and nitrogen in the ocean. Fungi are important decomposers in the ocean, but the impact of HABs on fungal community has not been elucidated. [Objective] Clarifying the influence of HABs on the fungal community is of great importance for further explaining the effect of HABs on material cycle in the ecosystem. [Methods] Through ITS1 amplicon sequencing, we analyzed the response of fungal community to an early-spring diatom bloom in 2017, in order to investigate the dynamic and co-occurrence patterns of the community. [Results] The alpha diversity indices of the fungal community changed significantly among four bloom stages, and they were all correlated with phosphate, nitrate, and nitrite (P<0.05). At the phylum level, the fungal community was dominated by Ascomycota (relative abundance:90.2%) and Basidiomycota (8.27%), among which Ascomycota was dominant across the four stages. At the class level, fungi from Leotiomycetes (16.1%) and Eurotiomycetes (9.3%) were the most abundant. The succession of fungal community was mainly driven by the abundance of harmful algal species, but changes in environmental factors including nitrate, nitrite, and phosphate were also responsible. Co-occurrence network was mainly composed of Helotiales, Eurotiales, Xylariales, Saccharomycetales, and Agaricostilbales. [Conclusion] The fungal community demonstrated obvious succession during the diatom bloom, which was mainly induced by diatom abundance, as well as environmental factors. The interaction of the fungal community within group was stronger than that between groups during the bloom, which is important for maintaining community stability.
