Scale-dependent influences on water quality, habitat, and fish communities in streams of the Kalamazoo River Basin, Michigan (USA)

In 2002, we investigated regional versus local influences of 22 streams in the Kalamazoo River basin, MI (USA) to: 1) determine how stream water quality, habitat, and fish communities were influenced by environmental variables at multiple spatial scales, and 2) examine linkages among watershed, riparian corridor (total and local stream corridors), and instream characteristics. Our data show that environmental patterns and processes operating at different spatial scales regulated stream water quality, habitat, and fish communities in Michigan streams. Broader spatial scales, including the watershed and total stream corridor (100-m riparian buffer extending the entire stream length upstream of the site), were the best predictors of water quality (Ra2  =  0.26–0.74), whereas the local stream corridor (50-m riparian buffer extending 200 m upstream of the site) was the best predictor of stream habitat (Ra2  =  0.23–0.59). Fish community structure was explained by various factors operating at both the watershed and local scales (Ra2  =  0.24–0.61). Anthropogenic factors (e.g., land use) had a greater influence on fish species composition (46% of the explained variation) than did natural environmental features (e.g., geology; 16%) or spatial variables (e.g., latitude, 13%). Understanding how environmental factors constrain stream ecosystem structure at multiple scales will help water resource specialists target appropriate scales and factors for management and restoration efforts.