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

Abstract:

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.