Eutrophication in subtropical lakes reinforces the dominance of balanced-variation component in temporal bacterioplankton community heterogeneity by lessening stochastic processes

This study first elucidates the shifts in the relative contributions of balanced-variation and abundance-gradient components to total temporal beta-diversity of bacterioplankton communities along the trophic state gradient, which are linked to the changes in the balance between deterministic and stochastic processes. Unveiling the rules of bacterioplankton community assembly in anthropogenically disturbed lakes is a crucial issue in aquatic ecology. However, it is unclear how the ecological processes underlying the seasonally driven bacterioplankton community structure respond to varying degrees of lake eutrophication. We, therefore, collected water samples from three subtropical freshwater lakes with various trophic states (i.e. oligo-mesotrophic, mesotrophic, and eutrophic states) on a quarterly basis between 2017 and 2018. To innovatively increase our understanding of bacterioplankton community assembly along the trophic state gradient, the total bacterioplankton community dissimilarity was subdivided into balanced variation in abundances and abundance gradients. The results indicated that balanced-variation component rather than abundance-gradient component dominated the total temporal beta-diversity of bacterioplankton communities across all trophic categories. Ecological stochasticity contributed more to the overall bacterioplankton community assembly in the oligo-mesotrophic and mesotrophic lakes than in the eutrophic lake. The reduced bacterioplankton network complexity at the eutrophic level was closely associated with the enhancement of environmental filtering, showing that bacterioplankton communities in eutrophic lakes are likely to be less stable and more vulnerable to water quality degradation. Together, this study offers essential clues for biodiversity conservation in subtropical lakes under future intensified eutrophication.

Automated summary

This study investigates the assembly process of bacterioplankton communities in anthropogenically disturbed lakes and finds that the balanced-variation component dominates the total temporal beta-diversity of bacterioplankton communities across different trophic categories. Ecological stochasticity contributes more to bacterioplankton community assembly in oligo-mesotrophic and mesotrophic lakes, while environmental filtering strengthens in eutrophic lakes, making bacterioplankton communities more vulnerable.