Microbial community assembly and co-occurrence patterns in Sanmen bay: A comparative analysis before and after...

The limited availability of historical data has resulted in the ongoing debate regarding the short-term effects of thermal discharge from nuclear power plants (NPPs) on microbial communities, including both prokaryotes and microeukaryotes. This study focused on the co-occurrence patterns, assembly processes, and community functions in the eutrophic coastal waters of Sanmen Bay (SMB) before and after NPP operation. Gammaproteobacteria and Alphaproteobacteria were the dominant prokaryotic taxa, while Dinoflagellates consistently maintained their prevalence in SMB. This suggests that short-term thermal discharge does not significantly alter the composition of microbial communities. The co-occurrence networks were primarily composed of Gammaproteobacteria, Alphaproteobacteria, Dinoflagellates, Diatoms, and Cryptophyta, with similar network topological properties across sampling groups. Homogeneous selection and dispersal limitation were the main mechanisms that controlled the assembly of microbial communities. Homogeneous selection was more significant for prokaryotes, while dispersal limitation was the dominant factor in microeukaryotes, irrespective of a thermal discharge. Prokaryotic β-diversity and nutrients showed substantially positive effects on the functional potential of the prokaryotic community. The findings indicate that short-term thermal discharge from the NPP, as long as they do not cause a significant overall temperature increase in the bay, are unlikely to impact the microbial communities within the coastal bay ecosystem.