Synchronous dynamics and correlations between bacteria and phytoplankton in a subtropical drinking water reservoir

TLDR

Phytoplankton and bacteria are abundant aquatic components, yet how phytoplankton succession shapes bacterial community composition remains largely unknown. The study aimed to assess correlations between bacterial and phytoplankton communities and quantify how phytoplankton succession drives temporal variation in bacterial community composition in Tingxi Reservoir. Bacterial communities were profiled by qPCR and 16S rRNA gene pyrosequencing, while phytoplankton were identified by light microscopy. Seasonal shift from Cyanophyta to Bacillariophyta accurately predicted bacterial OTU distribution, with most abundant OTUs positively correlated with phytoplankton, and structural equation modeling showed phytoplankton succession explained the largest portion of bacterial community variation.

Abstract

Both phytoplankton and bacteria are key and abundant components of aquatic ecosystems and play pivotal roles in maintaining ecosystem structure and function. However, the extent to which phytoplankton community succession influences changes in bacterial community composition (BCC) is largely unknown. In this study, we evaluated the correlations between bacteria and phytoplankton communities and determined the relative contribution of phytoplankton community succession to temporal variation of BCC in a subtropical drinking water reservoir (Tingxi Reservoir, southeast China). Bacterial communities were investigated by quantitative PCR and 454 pyrosequencing of 16S rRNA genes, while phytoplankton communities were analyzed by light microscopy. A remarkable seasonal succession from Cyanophyta to Bacillariophyta was observed during the study period, and this succession can accurately predict the distribution and abundance of the bacterial OTUs based on the discriminant function analysis. Association networks revealed that 38 of the 46 abundant bacterial OTUs exhibited significant correlations with phytoplankton. More interestingly, the positive correlations dominated the associated network, which may suggest that facilitative correlations between phytoplankton and bacteria are more important than inhibitory correlations in the Tingxi Reservoir. In addition, some bacterial OTUs were closely correlated with the dynamics of Microcystis, and they were affiliated with the divisions Acidobacteria, Actinobacteria, and Proteobacteria. Structural equation model showed that succession of phytoplankton community explained the largest part of temporal variation in BCC. Therefore, our data suggest that the distinct succession of phytoplankton community may mediate the temporal dynamics of bacterial community in the Tingxi Reservoir.