Eutrophication increases deterministic processes and heterogeneity of co-occurrence networks of bacterioplankton metacommunity assembly at a regional scale in tropical coastal reservoirs

Understanding microbial metacommunity assembly and the underlying methanisms are fundamental objectives of aquatic ecology. However, little is known about how eutrophication, the primary water quality issue of aquatic ecosystems, regulates bacterioplankton metacommunity assembly at a regional scale in reservoirs. In this study, we applied a metacommunity framework to study bacterioplankton communities in 210 samples collected from 42 tropical coastal reservoirs in the wet summer season. We found that the spatial pattern of bacterioplankton community compositions (BCCs) at a regional scale was shaped mainly by species sorting. The reservoir trophic state index (TSI) was the key determinant of bacterioplankton metacommunity assembly. BCC turnover increased significantly with the TSI differences between sites ( increment TSI) when increment TSI was 20, but remained at a level of about 80% when increment TSI was 20. Compared to oligo-mesotrophic and mesotrophic reservoirs, increased heterogeneity of co-occurrence bacterioplankton networks and bacterioplankton beta-diversity were observed across eutrophic reservoirs. We propose that larger variation in phytoplankton community assembly may play directly or indirectly deterministic processes in controlling the bacterioplankton metacommunity assembly and became the potential mechanisms behind the observed higher BCC heterogeneity across the eutrophic reservoirs. Our research contributes to a broader understanding of the ecological effects of eutrophication on reservoir ecosystems and provides clues to the management of the tropical coastal reservoirs.

Automated summary

This study investigated bacterioplankton communities in 42 tropical coastal reservoirs, finding that the trophic state index (TSI) of reservoirs was the key determinant of bacterioplankton metacommunity assembly. The heterogeneity of co-occurrence bacterioplankton networks and beta-diversity increased in eutrophic reservoirs compared to oligo-mesotrophic and mesotrophic reservoirs.