Colleen Flaherty

Advisor: Dr. Stanley Dodson

M.S. Zoology, 2003: The effects of pharmaceuticals on non-target organisms.

Pharmaceuticals have been globally detected in surface waters, and the ecological impacts of these biologically-active, ubiquitous chemicals are largely unknown. To evaluate the aquatic toxicity of several environmentally-detected pharmaceuticals, we performed single species laboratory toxicity tests with Daphnia magna, a common freshwater zooplankton. We conducted acute exposure (6-day) pharmaceutical bioassays, which simulated environmental pulse events and evaluated survivorship and morphology of adults and neonates, adult length, resting egg production, brood size (fecundity), and the proportion of male broods produced (sex ratio). Chronic exposure (30-day) bioassays evaluated pharmaceutical effects over the lifespan of female Daphnia. In general, exposure to a single pharmaceutical in the 1-100 µg/L range yielded no apparent effects on the normal life processes of Daphnia. However, chronic fluoxetine exposure (36 µg/L) significantly increased Daphnia fecundity, and acute clofibric acid exposure (10 µg/L) significantly increased sex ratio. A pharmaceutical cocktail (mixture) of fluoxetine (36 µg/L) and clofibric acid (100 µg/L) caused significant mortality. Lowering this cocktail’s clofibric acid concentration to 10 µg/L resulted in significant deformities, including malformed carapaces and swimming setae. Mixtures of three to five antibiotics elicited changes in Daphnia sex ratio. We concluded (1) individual and mixtures of pharmaceuticals affected normal development and reproduction of Daphnia magna, (2) aquatic toxicity of pharmaceutical cocktails can be unpredictable and complex compared to individual pharmaceutical effects, and (3), timing and duration of pharmaceutical exposure influenced aquatic toxicity.