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Publication Date

January 2001


Elevated concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides, and metals have been documented in bed sediments or in resuspended particles in water in the Barton Springs watershed located in Austin, Texas. The endangered Barton Springs salamander (Eurycea sosorum) inhabits the springs and concern has been expressed that sediments in the springs may be contaminated to concentrations that may be toxic to invertebrates that serve as a food source for these salamanders. Consensus-based probable effect concentrations (PECs) were used to predict the potential for toxicity in sediments collected from the springs. These PECs were developed to determine the concentration of contaminants above which adverse effects are likely to be observed to sediment-dwelling organisms. Mean PEC quotients (PEC-Q) were calculated to provide an overall measure of chemical contamination and to support an evaluation of the combined potential effects of multiple contaminants in sediments collected from the Barton Springs watershed. In addition, 28-d sediment toxicity tests were conducted with the amphipod Hyalella azteca with samples collected from Barton Springs Pool. Mean PEC-Q in sediments from the watershed were frequently elevated to levels that would be predicted to be toxic to sediment-dwelling organisms and elevated concentrations of PAHs contributed to these elevated quotients. Moreover, suspended particles collected from creek flow and spring discharge indicate that run-off during storm events is likely contributing to this contamination. Sediments from the Barton Springs watershed were toxic to H. azteca following exposure of amphipods to low irradiance of ultraviolet radiation (UV-B). Results of these evaluations indicate that sediments in watershed are contaminated with PAHs to concentrations that are likely toxic to invertebrates that serve as a food source for the endangered salamanders. Concentration of organochlorine pesticides are also elevated in sediment samples and may pose a risk to sediment-dwelling organisms inhabiting the watershed. However, organochlorine pesticides were not included in this evaluation because reliable PECs have not be developed for these compounds. Additional studies are needed to determine: (1) the depth of UV-B penetration into the water column within the watershed during different times of the year, (2) the contribution of UV-B to the toxicity of contaminants to organisms inhabiting the watershed, and (3) the risks of exposure to organochlorine pesticides to organisms inhabiting the watershed. Open Access - Permission by Publisher See Extended description for more information.


United States, Geology






U.S. Fish & Wildlife Service





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