Influence of urbanization on a karst terrain stream and fish community

摘要

Effects of catchment urbanization described as the urban stream syndrome generally result in an altered fish community with headwater stream fish communities particularly vulnerable to changes associated with urbanization. In this study, we considered how the fish community in a Central Texas headwater karst stream changed with catchment urbanization. Paleohistory and a narrative on urbanization within the upper San Marcos River were compiled and qualitatively related to historical fish changes from 1880 to 2011 to test predictions of the urban stream syndrome. Our predictions of decreases in native fish community and species abundances were largely unsupported despite 170 years of urbanization, specifically anthropogenic alterations to instream and catchment habitats, water quantity and water quality, stream morphology, and introduced species. Overall, the upper San Marcos River supports a persistent (＞60 %) fish community through time with observed native species declines and extirpations not attributed solely to urbanization within the catchment. As such, we conclude that upper San Marcos River is largely an exception to the urban stream syndrome, which we attribute to two mechanisms; 1) paleohistory of the upper San Marcos River suggests a dynamic stream system with decreasing stream flow and increasing water temperatures since the last glacial maximum, and 2) water quantity of the San Marcos River is much greater than water quantity of other headwater streams used to assess urban stream syndrome. Nevertheless, the lower portion of the upper San Marcos River is indicative of an altered system, in both habitat and fish community, and represents a target area for rehabilitation.