Browsing by Subject "Toxicity testing."
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Item Prymnesium parvum in inland waters : comparative toxicity, microcystin allelopathy, and toxin photodegradation.(2009-09-09T14:24:25Z) James, Susan Virginia.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.The harmful algal species Prymnesium parvum, a toxin-producing mixotrophic haptophyte, has caused massive fish kills in slightly saline inland Texas water bodies. In the first study, standardized aquatic test models from multiple trophic levels were simultaneously employed to compare sensitivities to P. parvum toxins. Fish mortality was the most sensitive endpoint, though adverse reproduction effects in two invertebrate species were observed; a green algal species was not adversely affected. A second study employed a probabilistic risk assessment approach and examined potential allelopathy of the cyanotoxin microcystin-LR to P. parvum. A concentration of 4,392.8 μg l⁻¹ significantly inhibited P. parvum growth over a portion of the study, which corresponded to a 9% probability of detecting this concentration in the environment. Finally, the effect of sunlight on toxicity of P. parvum cell-free filtrate was assessed. Exposure to eight hours of full or ~50% sunlight eliminated toxicity to Pimephales promelas, suggesting toxin photodegradation.Item Quantifying the presence of current-use insecticides and toxicity of sediments in urban residential watersheds in central Texas.(2007-12-03T18:45:25Z) Hintzen, Emily P.; Belden, Jason B.; Environmental Studies.; Baylor University. Dept. of Environmental Studies.In the US, residential use of pyrethroid and other recently developed insecticides has increased substantially in recent years, yet the impact of these insecticides on benthic invertebrates in urban streams is largely unknown. The objective of this study was to determine the presence and concentration of current-use pesticides in the sediments of residential streams in central Texas. Additionally, the toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a pesticide application season. The sediments were extracted and analyzed using a Varian 2100 gas chromatograph with MS/MS for the presence of several pyrethroids and other common insecticides. Ten-day sediment toxicity tests using H. azteca were also conducted with the sediment samples. Results of this study suggest that pyrethroid insecticide contamination of urban sediments may indeed be a concern in central Texas.