Response of Chironomidae communities to land use in an urban stream

Land use patterns influence biota of urban streams by cumulative percent and spatial arrangement of impermeable surfaces (IS). Six sites along stream reaches of Minnehaha Creek, an urban stream in Minneapolis, are being studied to determine how communities of chironomids respond to variations of cumulative IS versus local buffer areas adjacent to creek beds near sample sites. Spatial buffers considered to improve creek health are those with less than 25% IS. We used collections of surface-floating pupal exuviae to quantify responses, using species richness, taxonomic composition and phenological overlap as response variables. Chironomid exuviae provide a spatially integrated index of diversity because genera and species vary in microhabitat requirements and are good indicators of changes in stream physical and chemical conditions. We will test the hypothesis null hypothesis that increased small-spatial buffering within the riparian zone can moderate the cumulative amount of IS upstream of sample sites.