Author: Gregory J. Knothe

Publisher:

Published: 2012

Total Pages: 466

ISBN-13:

Streams throughout the U.S. have been historically subjected to degradation due to urbanization, agriculture and industry. The influence of urbanization on stream ecosystems is difficult to evaluate, due to many interacting variables. Previous studies have found that the degree of urbanization influences flow regime, pollutant loading and resulting fish community structure. Our study investigated the influence of urbanization on hydrology, physical habitat, water quality, and resulting fish community structure at 8 coastal streams located in Southeastern Texas. Streamflow, physical habitat, water quality and fish community data were collected at these sites during 2011. The stream sites were selected to represent a variety of land uses ranging from highly urbanized, to minimally urbanized or reference conditions. In order to determine the degree of urbanization within each watershed ArcGIS software was used to assess land use. Total impervious area (TIA) and percent impervious area (PIA) was used for each watershed as a simple index of urbanization. TIA and PIA were estimated using 2006 impervious surface data obtained from the United States Geological Survey. Various fish community metrics including the Index of Biological Integrity (IBI), Shannon-Weiner diversity index, Pielou's evenness and species richness, were used to evaluate the impact of urbanization on fish community structure. Estimated land use data was compared to IBI scores, fish community metrics, water quality, and physical habitat. Several statistical analysis methods including Pearson correlation analysis, Analysis of Variance (ANOVA), principle component analysis and cluster analysis were used to evaluate the response of fish communities to land use and associated hydrology, physical habitat, and water quality. We found that IBI scores and stream fish diversity were negatively correlated with PIA. We also observed positive correlations between PIA/TIA and orthophosphate and combined nitrate and nitrite concentrations among the sites. We did not observe any strong correlations between the amount of impervious area within the upstream watershed and physical habitat metrics, with the exception of a negative correlation between TIA with mean instream cover, riparian width and tree canopy cover. Our study suggests that future management plans could include a threshold of impervious area for a watershed, in order to protect or promote biological integrity and water quality.