Temporal Evolution of Bacterial Community Structure, Co-Occurrence Patterns, and Community Assembly Process in Epiphytic Biofilms of Submerged Plants in a Plateau Lake

In shallow macrophytic lakes, epiphytic biofilms are formed on the surface of submerged plant stems and leaves because of the accumulation of algae and bacteria. Epiphytic biofilms have a significant impact on the health of the host vegetation and the biogeochemical cycling of lake elements. However, there is a lack of understanding of the community diversity, species interactions, and community assembly mechanisms in epiphytic bacterial communities (EBC) of plants during different growth periods. We investigated the successional dynamics, co-occurrence patterns, and community building processes of epiphytic biofilm bacterial communities of typical submerged plants, Najas marina and Potamogeton lucens from July, 2020 to November, 2020. The results showed that EBC diversity and abundance varied significantly among seasons, community diversity and abundance increased gradually from July to November, and temperature was the best explanatory factor for predicting seasonal changes in EBC community structure. Co-occurrence network analysis revealed that the average degree and plot density of the network gradually increased from July to November, indicating that the complexity of the EBC network gradually increased. The bacterial community co-occurrence network is mainly limited by temperature, pH, and transparency. The phylogeny-based null model analysis showed that microbial community construction was dominated by deterministic processes in different periods, and their contribution tended to increase gradually. Additionally, we found that as the dominant role of deterministic processes gradually increased, the microbial co-occurrence links also increased and the potential interrelationships between species became stronger. Altogether, these findings provide insights into the seasonal variability of EBC assemblage and co-occurrence patterns in lacustrine ecosystems.