Psychotropic Pharmaceuticals in Aquatic Systems: An Ecological Perspective

Psychotropic pharmaceuticals have been shown to exert a variety of sublethal effects on non-target organisms, even at low concentrations found in the environment (ng/L to µg/L); hence, the aim of my research has been to determine the individual-level effects of psychotropic pharmaceuticals (the selective serotonin reuptake inhibitors sertraline and fluoxetine, and the β-blocker propranolol) on behavioral and life history traits in freshwater organisms. Further, this research was directed towards assessing the potential large-scale impacts of these effects on population growth and predator-prey interactions (with community-level implications) via the application of traditional, ecological concepts and models. This work has therefore incorporated the exposure of organisms to key biotic stressors connected with predator-prey interactions (e.g. non-consumptive effects, variations in diet composition or prey density) that serve as vital links across levels of organization.

The studies included in this thesis indicate that exposure to sertraline resulted in alterations in habitat choice of snails (Radix balthica), though this did not affect the predator-induced, non-consumptive effects in snail behavior. This suggests that sertraline may not increase risk for predation by fish. Also, fluoxetine exposure altered risk-taking behavior in fish (Perca fluviatilis) linked to decreased vulnerability to avian predation, but this was potentially at the cost of reduced food-intake. A separate study directly examined feeding in juvenile fish (Perca fluviatilis) for which those exposed to sertraline exhibited decreased feeding rates at both low and high zooplankton prey densities (Daphnia magna). When examining effects of sertraline on the zooplankton Daphnia magna, I also detected significant reductions in growth, fecundity, and capacity for population increase, especially when exposed to both sertraline and a toxic cyanobacterium, Microcystis aeruginosa, simultaneously, i.e. with synergistic effects due to exposure to the two stressors occurring at high sertraline concentrations.

When employed within an ecological framework, scientific research on organism-level traits as endpoints of the short-term effects of chemical contaminant exposure can provide valuable information on the potential long-term outcomes of exposure in the environment. Not only are these effects of exposure interesting in themselves, but more importantly, the goal of this work has been to enable a holistic approach to ecotoxicology by determining how these behavioral and other trait-related effects impact the interactions among organisms, and the potential consequences thereof at higher levels of organization.