Dredging alleviates cyanobacterial blooms by weakening diversity maintenance of bacterioplankton community

Disentangling ecological mechanisms behind dredging is meaningful to implement environmental policy for improving water quality. However, environmental adaptation and community assembly processes of bacterioplankton in response to dredging disturbance are poorly understood. Based on Illumine MiSeq sequencing and multiple statistical analyses, we estimated interactions, functions, environmental breadths, phylogenetic signals, phylogenetic clustering, and ecological assembly processes of bacterioplankton community before and after dredging. We found distinct change in community composition, comparable decreases in diversity, functional redundancy and conflicting interaction, relatively low phylogenetic clustering, and relatively weak environmental adaptation after dredging. The bacterioplankton community assembly was affected by both stochastic and deterministic processes before dredging, but dominated by stochasticity after dredging. Sediment total phosphorus was a decisive factor in balancing determinism and stochasticity for bacterioplankton community assembly before and after dredging. Consequently, taxonomic and phylogenetic alpha-diversities of bacterioplankton exhibited higher contributions to the water trophic level represented by chlorophyl alpha before dredging than afterwards. Our results emphasized bacterioplankton in response to environmental changes caused by dredging, with nutrient loss and ecological drift playing important roles. These findings extend knowledge of contribution of bacterioplankton diversity to water trophic level and decipher mechanisms of bacterioplankton diversity maintenance in response to dredging, which is useful for guiding mitigation of cyanobacterial blooms.

Automated summary

The study investigates the ecological mechanisms behind dredging and the adaptation of bacterioplankton community to dredging disturbance. It reveals distinct changes in community composition, diversity, and interactions, with sediment total phosphorus playing a crucial role in balancing deterministic and stochastic processes in bacterioplankton community assembly before and after dredging. The research highlights the importance of understanding the contribution of bacterioplankton diversity to water trophic level and provides insights into the maintenance of bacterioplankton diversity in response to dredging, which is helpful for mitigating cyanobacterial blooms.