Divergent biodiversity responses of multitrophic aquatic communities to hydrological connectivity and land-use...

Loss of hydrological connectivity (HC) and increases in land-use intensity (LUI) driven by human activities have become major threats to global freshwater biodiversity. Although most studies have examined the influences of HC and LUI on freshwater communities using a single taxonomic group, our understanding of whether multitrophic aquatic communities exhibit divergent or convergent responses to these environmental drivers remains limited. In this study, assemblages of benthic algae, benthic macroinvertebrates, and fish were investigated to evaluate the responses of multitrophic aquatic communities to HC and LUI in a boreal river basin of northern China. Our data revealed the following patterns: First, the species composition of multitrophic aquatic communities exhibited convergent responses to HC and LUI. Notably, a reduction in HC or an increase in LUI was associated with a decline in the proportion of sensitive taxa and an increase in tolerant taxa. Second, responses of multitrophic aquatic biodiversity to variation of HC and LUI differed among different taxonomic groups. For instance, α-diversity of fish declined with decreasing HC, whereas α-diversity of benthic macroinvertebrates increased with decreasing HC. Increased LUI promoted α-diversity of fish; however, it suppressed that of benthic macroinvertebrates. Additionally, loss of HC reduced β-diversity of fish and benthic macroinvertebrates, while LUI increased β-diversity of both communities. Third, stochastic processes played an important role in the community assembly of multitrophic aquatic groups across HC and LUI gradients. Finally, HC regulated the biodiversity of multitrophic aquatic communities by influencing hydrological conditions, whereas LUI affected the biodiversity of those groups by altering water quality conditions. Overall, these findings suggest that multitrophic aquatic communities may display convergent and taxon-specific responses to HC and LUI. These results emphasize the importance of multitrophic aquatic communities when assessing the ecological impacts of anthropogenic stressors on freshwater ecosystems.