Structural and Functional Diversity of the Microbiome During the Phaeocystis Globosa Winter Bloom in the Southern Yellow Sea of China

Phytoplankton blooms affect the microbial community seriously in marine ecosystems. Here, we used 16 S rRNA gene high-throughput sequencing and functional prediction to reveal the microbiome communities in different stages of the Phaeocystis globosa bloom in the southern Yellow Sea in December 2021. The total microbial abundance and diversity increased from the middle to the late stage of the bloom, but the dominant taxa remained the same, including Alphaproteobacteria, Bacteroidia, and Gammaproteobacteria. In terms of temporal changes, the abundance of Alphaproteobacteria decreased significantly over time (p < 0.05). The dominant families in both periods were Rhodobacteraceae and Flavobacteriaceae, but their abundance varied significantly over time (p < 0.05), for the proportion of Rhodobacteraceae decreased from 51.05% to 43.55%, while the Flavobacteriaceae increased from 16.60% to 20.91%. Other less abundant but important functional groups also varied significantly over time, with the percentage of Comamonadaceae decreased (p < 0.001), while Methyl-ophagaceae and Microbacteriaceae increased dramatically (p < 0.01). The predicted functions of the microbial communities were characterized by chemoheterotrophy, oxidation of sulfur, sulfur compounds and sulfite, and reduction of nitrate, and significant differences were also observed between stages and fractions. Multiple environmental factors (temperature, phosphate, silicate, and colony density) showed significant effects on the microbial community, and phylogenetic-based mean nearest taxon distance (MNTD) analyses indicated that stochastic processes were more important in governing the spatiotemporal assembly of the microbiome during the bloom. Overall, the microbial responses to the P. globosa bloom suggested a substrate-controlled succession in the microbiome communities.