Relationships among the landscape, stream habitat, and stream biota of the Huron and Raisin Rivers, southeastern Michigan.

Both anthropogenic and natural landscape features influence the biological assemblages of streams, and one mechanism by which this occurs is through landscape's influence on stream habitat. This study considers these relationships for 46 subcatchments of the Huron and Raisin Rivers, southeastern Michigan. Landscape's influence on gradients in stream habitat was considered first. Natural and anthropogenic landscape features were derived for stream catchments, and anthropogenic land uses were also summarized for stream buffers and by pattern metrics. Using principal component analysis (PCA), four gradients were identified explaining a majority of variation in habitat including habitat complexity, substrate diversity, flow stability, and channel size. Using multiple linear regression, habitat measures were predicted from landscape features, and natural landscape features were found to explain more variance in stream habitat than did anthropogenic land use. Effects of the landscape on the region's fish and macroinvertebrate assemblages were examined next. Separate classifications of fish and macroinvertebrates revealed distinct biological groups related to specific land uses. Both fish and macroinvertebrate groups were associated with high levels of forests and wetlands, agriculture, and exurban development. Further, fish and macroinvertebrates dominating similar groups shared morphological characteristics and tolerance to stressors. Despite these similarities, results of the classification and an investigation of gradients in the biological assemblages revealed only weak community concordance between the fish and macroinvertebrates of the region. Finally, relationships among the landscape, habitat gradients, and biological assemblages were investigated using Covariance Structure Analysis. In these analyses, fish and macroinvertebrate assemblages were described by richness and diversity and by PCA axes summarizing trophic guilds, habitat preferences, and tolerances of each taxonomic group. Results demonstrated differences in the response of fish vs. macroinvertebrates to the influence of landscape through habitat. Also, natural landscape features, including agriculture and urban development, had stronger effects on habitat, and consequently, on biota, than did anthropogenic land use. By establishing links among the landscape, stream habitat, and the biological assemblages of streams, this investigation provides insights into mechanisms that influence the biological integrity of streams.Ph.D.Aquatic sciencesBiological SciencesEcologyEnvironmental scienceHealth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124822/2/3163829.pd