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Abstract
Since the establishment of the US Clean Water Act in 1972, biologicalassessments using fish and macroinvertebrates have been employed to detect streamperturbations and are required to assess water quality in locations across the globe.Despite the widespread use of such techniques, many questions remain unansweredconcerning relationships between biological factors and physical habitat. As Georgiacontinues to grow, it is important to identify how that growth will impact aquaticcommunities and water quality. A better understanding of linkages between ecologicaldrivers and aquatic communities is useful for predictive modeling of watershedconditions and the development of management strategies, providing suggestions to helpmaintain or improve the health of a watershed. This study investigates relationshipsbetween aquatic communities and 1) urbanization and 2) turbidity, SSC, and percentfines, as well as examining interrelationships between fish and macroinvertebrateassemblages. Our results indicate biotic community metrics were highly sensitive to landcover, specifically the fractions of urban land, imperviousness, and forest. Nearly all fair,good, and excellent fish IBI scores occurred in basins with more than 50 percent forestand less than 15 percent urban area and less than 4 percent impervious surface, indicatingthat Georgia Piedmont streams may be more sensitive to urbanization effects thanstreams in other parts of the country. Overall, sites with less urbanization had greaterlitter standing crops during December; however, higher rates of retention occurred inmore urbanized areas. We infer that urban streams balance litter export with additionalhorizontal inputs from storm drains that act to increase the litter source area.Macroinvertebrate shredder taxa richness was negatively affected by watershed landuse,but shredder abundance and percent composition were not. Shredder abundance andcomposition were not correlated to litter availability. Neither baseflow suspendedsediment concentrations, baseflow turbidity, nor bed particle size distributions weresignificantly related to watershed imperviousness or other land use metrics. However,these metrics added significantly to explanatory models of important biological metrics.Macroinvertebrate and fish biotic indices do not provide the same information withregard to water quality, although fish index of well being scores are more highlycorrelated than IBI scores.