Effects of environmental factors on mycoplankton diversity and trophic modes in coastal surface water

Mycoplankton play a key role in aquatic microbial food webs and nutrient cycling. However, the environmental factors that affect their composition and trophic modes in coastal water remain unclear. In this study, we used fungal metabarcoding to characterize seasonal mycoplanktonic communities in the surface water of the Maowei Sea. Dothideomycetes and Sordariomycetes were the dominant classes in the Maowei Sea. Random forest modeling analyses suggested that Ochroconis, Rhodotorula, Perenniporia and Derxomyces were the best seasonal bioindicators of environmental changes. Spearman's correlation analysis showed that TOC (total organic carbon) is the main factor affecting mycoplanktonic bioindicators. Through FUNGuild analysis, we classified mycoplankton in the Maowei Sea into eight trophic modes and found that saprotrophs were the most abundant. Random forest analysis and Spearman's correlation indicated that the mycoplankton trophic modes could reflect environmental changes in the Maowei Sea and were mainly influenced by dissolved inorganic phosphorus (DIP), dissolved oxygen (DO), and total organic carbon (TOC). Mycoplanktonic alpha and beta diversities significantly varied in different seasons (p < 0.05). Spearman rank's test, Mantel test, and partial Mantel test indicated that TOC was the key environmental factor that affected the mycoplanktonic alpha and beta diversities. Variation partition analysis revealed that mycoplankton community structure was affected more due to nutrient variability than water quality (18 % vs 7 %). Overall, this study enhanced our understanding of the key controlling environmental factors affecting mycoplanktonic diversities and trophic modes in the coastal environment.