EXAMINING LAND-USE INFLUENCES ON STREAM HABITATS AND MACROINVERTEBRATES - A GIS APPROACH

Geographic Information Systems (GIS) were used to assess the relations hips between land use patterns and the physical habitat and macroinver tebrate fauna of streams within similar sized watersheds. Eleven secon d or third order watersheds ranging from highly urbanized to heavily f orested were selected along Lake Superior's North Shore. Land use patt erns within the watersheds were quantified using readily available dig ital land use/land cover information, with a minimum mapping resolutio n of 16 ha. Physical habitat features, describing substrate characteri stics and stream morphology, were characterized at sample points withi n each stream. Principle component and correlation analyses were used to identify relationships between macroinvertebrates and stream physic al habitat, and between habitat and land use patterns. Substrate chara cteristics and presence of coarse woody debris were found to have the strongest correlations with macroinvertebrate assemblage richness and composition. Agricultural and urban landuse was correlated with substr ate characteristics. Algal abundance, associated with macroinvertebrat e compositional differences, was correlated with housing density and n on-forest land covers. The use of readily available spatial data, even at this relatively coarse scale, provides a means to detect the prima ry relationships between land use and stream habitat quality; finer-re solution GIS databases are needed to assess more subtle influences, su ch as those due to riparian conditions.