Stream macroinvertebrate community metrics consistently respond to a spatiotemporal disturbance gradient but composition is more context-dependent

ContextImproving our understanding of how riverine communities respond to anthropogenic change requires spatial comparisons across multiple sites, high-resolution temporal analyses, and examination of both taxa and trait responses. However, studies that encompass all these aspects remain scarce.ObjectivesWe used 10 years of annual monitoring data from 14 sampling sites in the Rhine-Main-Observatory (a Long-Term Ecological Research-LTER-site in Germany) to investigate spatiotemporal responses of stream macroinvertebrate communities along anthropogenic disturbance gradients (measured as 'ecological quality').MethodsWe examined spatiotemporal changes in various community components, including taxa, traits, metrics summarizing community responses (e.g., richness), and community composition.ResultsSpatially, consistent patterns over a decade of sampling revealed that less-disturbed communities were characterized by higher taxonomic and trait diversity and occurrence of pollution-sensitive taxa. Anthropogenic disturbance tended to become less severe through time, particularly in more upstream sites, likely driven by improvements in land-use and water quality. Conversely, more downstream sites exhibited a lesser degree of improvement (or none at all) likely owing to persistent or cumulative stressors. Overall, taxonomic/trait metrics consistently reflected the magnitude of the environmental improvement, while community composition did not, suggesting a weaker link between community changes and anthropogenic impacts severity.ConclusionOur results emphasize the importance of accounting for the variability in community responses to anthropogenic changes, and identifying optimal monitoring strategies to track such responses. In heterogeneous catchments, choosing which community component to focus and where to locate monitoring sites (e.g., monitoring ecological quality for the EU Water Framework Directive) can determine a timely detection of anthropogenic impacts.

Automated summary

This study used 10 years of monitoring data from 14 sampling sites in Germany to investigate the spatial and temporal responses of stream macroinvertebrate communities to anthropogenic disturbance.