Compensatory dynamics of lotic algae break down nonlinearly with increasing nutrient enrichment

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