广西北部湾茅尾海浮游真菌群落结构及其影响因子

浮游真菌在海洋食物网和生物地球化学循环中发挥着关键作用。【目的】为解析广西北部湾茅尾海不同季节浮游真菌群落结构及其关键环境影响因子，于2017年7月(夏季)、9月(秋季)、12月(冬季)和2018年3月(春季)期间在该海域设置7个站点，采集表层海水样品。【方法】利用内部转录间隔区(internal transcribed spacer, ITS)基因高通量测序技术，分析茅尾海浮游真菌群落结构与多样性。【结果】茅尾海海域浮游真菌隶属6个门、26个纲、71个目、167个科、282个属和374个种。主要浮游真菌类群为子囊菌门(Ascomycota, 82.14%)和担子菌门(Basidiomycota, 10.74%)，共占浮游真菌总丰度的92.88%。茅尾海浮游真菌群落Shannon指数和Simpson指数在春季最高，Chao1指数和丰富度(richness)指数在冬季最高。主坐标分析(principal coordinates analysis, PCoA)和相似性分析(analysis of similarities, ANOSIM)结果显示，不同季节浮游真菌群落的β多样性具有极显著差异(R=0.591 2, P<0.001)。通过随机森林模型分析(random forest modeling analysis, RF)，发现黄曲霉(Aspergillus flavus)、二色胶孔菌(Gloeoporus dichrous)、杂色曲霉(Aspergillus subversicolor)和微扁沃利雅炭皮菌(Whalleya microplaca)、翹鱗香菇(Lentinus squarrosulus)等20种海洋浮游真菌对环境变化敏感，可用于评估茅尾海富营养化状况。Spearman相关性分析表明，浮游真菌α多样性与海水pH、盐度和溶解氧(dissolved oxygen, DO)呈显著正相关关系(P<0.05)，与温度、叶绿素-a (chlorophyll a, Chl-a)以及总有机碳(total organic carbon, TOC)呈显著负相关关系(P<0.05)。方差分解分析(variance partitioning analysis, VPA)发现营养因子是浮游真菌群落结构的主要驱动因子。【结论】本研究可为揭示北部湾海洋浮游真菌多样性提供理论参考，并为茅尾海生态环境监测与资源利用提供科学依据。

Mycoplankton community structure and its influencing factors in the Maowei Sea of the Beibu Gulf, Guangxi

Mycoplankton play a key role in the marine food web and biogeochemical cycling. Objective] To reveal the community structures of mycoplankton across different seasons and their key environmental drivers, we collected the surface water samples from seven stations in July (summer), September (autumn), and December (winter) 2017 and March (spring) 2018 in the Maowei Sea, Beibu Gulf, Guangxi Zhuang Autonomous Region. Methods] We employed high-throughput sequencing of the internal transcribed spacer (ITS) gene to analyze the community structure and diversity of mycoplankton. Results] The mycoplankton in the Maowei Sea belonged to 374 species, 282 genera, 167 families, 71 orders, 26 classes of 6 phyla. Ascomycota (82.14%) and Basidiomycota (10.74%) were the dominant phyla, with the total relative abundance of 92.88%. The Shannon and Simpson indices of the mycoplankton were the highest in spring, while the Chao1 and Richness indices were the highest in winter. Furthermore, the results of principal coordinate analysis (PCoA) and analysis of similarities (ANOSIM) showed that there was a significant difference in the beta diversity of mycoplankton community among different seasons (R=0.591 2, P<0.001). The random forest modeling analysis (RF) revealed that 20 species of mycoplankton including Aspergillus flavus, Gloeoporus dichrous, Aspergillus subversicolor, Whalleya microplaca, and Lentinus squarrosulus were sensitive to environmental changes and could be used to assess the eutrophication status of the Maowei Sea. The Spearman correlation analysis showed that the alpha diversity of mycoplankton was positively correlated with seawater pH, salinity, and dissolved oxygen (P<0.05) and negatively correlated with temperature, chlorophyll-a (Chl-a), and total organic carbon (P<0.05). The variance partitioning analysis (VPA) indicated that nutrients were the key factors affecting the community structure of mycoplankton. Conclusion] This study provides a theoretical reference for revealing the diversity of marine mycoplankton in Beibu Gulf and a scientific basis for eco-environment monitoring and resource utilization in the Maowei Sea.