16S community composition of metal-contaminated freshwater sediments.. freshwater sediment clone ensemble

A conceptual model for how persistent environmental stressors shape ecosystem function and community structure in the long-term (e.g. years to centuries) would provide a foundation for predicting responses to chronic perturbations (e.g. persistent pollutants, climate change, etc.) and facilitate assessments of natural resource damage and management decisions. We hypothesized that communities exposed to persistent environmental stressors will develop tolerance - resulting in species-diverse communities with suppressed ecosystem function - and that patterns of α-diversity, β-diversity, and function will vary from those observed in response to acute stressors. We studied a century-old, 400 km long, heavy metal contamination gradient in the Clark Fork River in Western Montana, measuring hyporheic microbial community structural and functional variables. Microbial community structure and function correlated with contaminants while species richness and diversity were unaffected. These results suggest that ecosystem diversity recovers over evolutionary time, whereas a chronic stressor can impose continual costs on ecosystem function.