象山港硅藻赤潮过程中真菌群落演替及互作特征

Succession and interaction of fungal community during a diatom bloom in Xiangshan Bay

摘要:

[背景] 近岸海域赤潮的发生能显著改变包括真菌在内的微生物群落组成，进而影响海洋中碳氮元素循环。真菌是海洋中重要的分解者，但赤潮过程对真菌群落的影响少有报道。[目的] 探明赤潮过程对真菌群落的影响，对进一步阐释赤潮对生态系统中物质循环的影响具有重要意义。[方法] 针对2017年春季象山港硅藻赤潮，对真菌内源转录间隔区1（Internally Transcribed Spacer 1，ITS1）序列进行高通量测序，研究赤潮过程中真菌群落响应及共现性特征。[结果] 真菌群落的α多样性指数在赤潮暴发的各阶段差异显著，而且均与磷酸盐、硝酸盐和亚硝酸盐有显著相关性（P<0.05）。子囊菌门（Ascomycota，90.2%）和担子菌门（Basidiomycota，8.27%）是本次硅藻赤潮的优势菌门，其中子囊菌门遍布赤潮暴发的4个阶段；锤舌菌纲（Leotiomycetes，16.1%）和散囊菌纲（Eurotiomycetes，9.3%）是纲水平上的主要优势类群。赤潮暴发过程中硝酸盐、亚硝酸盐、磷酸盐和温度等环境因素的改变，驱动真菌群落组成及结构发生显著变化。Helotiales、Eurotiales、Xylariales、Sacc haromycetales和Agaricostilbales构成了真菌群落共现网络的主体。[结论] 真菌群落在赤潮的各阶段具有显著的演替特征，赤潮藻生消是引起真菌群落演替的主要因素，但是环境因子也扮演着重要角色。赤潮过程中，真菌群落同类群内的互作要强于不同类群间的互作，这对维持群落的稳定性具有重要意义。

关键词:硅藻赤潮;真菌群落;高通量测序;象山港

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.

Key words:diatom bloom;fungal community;high-throughput sequencing;Xiangshan Bay