Use of a Preliminary Index of Biotic Integrity in Urban Streams Around Atlanta, Georgia
DeVivo, Joseph C.
Couch, Carol A.
Freeman, Byron J.
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Data from 44 fish assemblage surveys conducted by the U. S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) program at 21 stream sites in the vicinity of Metropolitan Atlanta were analyzed to develop a preliminary Index of Biotic Integrity (IBI) for second- to fourthorder streams of the upper Chattahoochee River basin. Thirteen metrics commonly used in IBIs were evaluated by comparing observed responses in the NAWQA data along a gradient of urbanization to expected responses based on the findings of other IBI studies. The urbanization gradient was determined by Principal Components Analysis (PCA) of water and sediment chemistry data. PCA axis 1 scores, which accounted for 55.3 percent of the variance in the data, were strongly positively correlated with human population density (r2 = 0.64, p= 0.003). Eight metrics were selected• for inclusion in the preliminary IBI: percentage of 1) gravel-dwellers, 2) benthic invertivores, 3) generalized feeders, and 4) non-native fishes; 5) number of native sucker and 6) minnow species; 7) native species diversity; and 8) identity of or the dominant nest-associate cyprinid. A ninth sensitive metric, the percentage of tolerant individuals, was omitted from the IBI because it was autocorrelated with the percentage of non-native fishes.