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UBC Theses and Dissertations

Pharmaceuticals in stream ecosystems : the effects of chronic chemical (carbamazepine and fluoxetine) exposure on macroinvertebrate communities Colletti, Kay


Anthropogenic pollutants in freshwater systems are an emerging source of concern for researchers as an ever-increasing number of novel chemicals enter these systems via wastewater. The interactions between these compounds and environmental differences such as pH on freshwater organisms are not well understood, despite their near ubiquitous detection. Differences in environmental pH conditions are especially salient because the effects of pharmaceuticals are often pH dependent. The pharmaceuticals carbamazepine and fluoxetine are among the most frequently detected in affected surface waters. Carbamazepine is an anticonvulsant used to treat epilepsy and bipolar disorder, with known neuro-endocrine disruptive potential in stream macroinvertebrates. Fluoxetine is a serotonin reuptake inhibitor (SSRI) commonly used to treat depression and anxiety. Serotonin is key for many physiological functions in insects. The community-level effects on freshwaters from chronic exposure to environmentally relevant concentrations of the anticonvulsant carbamazepine and the SSRI fluoxetine on macroinvertebrates was investigated using mesocosms in two experiments. In both experiments communities were exposed to a single dose of 100 ng/L carbamazepine, 20 ng/L fluoxetine, or a combination of the two chemicals for 14 days. Carbamazepine caused a significant 8% reduction in predator populations compared to control treatments. Additionally, the abundance of early instar nemourids was 6.2 times greater in carbamazepine treatments than in all other treatments, which indicated that carbamazepine may influence developmental processes in some nemourid stoneflies. In the second experiment, pH was manipulated from pH 7 to pH 8 to explore how altering pH changes the metabolization, and subsequent community response, of ionizable pharmaceuticals. A higher pH did increase the negative effects of fluoxetine on macroinvertebrate community composition, resulting in a significant reduction in iv taxa evenness and total macroinvertebrate abundance. However, the community effects of carbamazepine and fluoxetine were not consistent between experiment, with experimental timing (seasonality) and the added variable of increased pH affecting the community responses. The inconsistencies in results emphasize some of the challenges faced when trying to determine effects of novel pharmaceutical pollutants due to the highly variable responses depending on environmental and biotic contexts being exposed to these pollutants.

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