Master of Science (MS)


Plant, Environmental Management and Soil Sciences

Document Type



Damaging and often irreversible effects occurring in aquatic ecosystems have recently been linked to the presence of pharmaceuticals in water bodies. Because this crisis has only recently been identified, existing reports on the consequences of this contamination are scarce. In EPA standard acute effluent toxicity tests, Ceriodaphnia dubia, Daphnia pulex, Pimephales promelas, Mysidopsis bahia, and Menidia beryllina were subjected to two of the most widely distributed pharmaceuticals in the U.S., ethinyl estradiol (EE2), a synthetic form of estrogen, and fluoxetine HCl (FLX), the active ingredient in Prozac®, for 96 hours to assess and evaluate toxic responses. After test termination, mortality curves were statistically analyzed to quantify 96 hour median effective concentrations (EC50s), no observable effect concentrations (NOECs), lowest observable effect concentrations (LOECs), and chronic values (Ch.V.s). Derived EC50s for both drugs identified C. dubia as the most sensitive organism. In terms of the Ch.V., C. dubia was the most sensitive organism administered EE2 and M. bahia given FLX. The most resilient species was P. promelas regarding the EC50 after EE2 dosing, D. pulex in respect to the Ch.V. after EE2 dosing, and M. beryllina pertaining to the EC50 and Ch.V after FLX dosing. Existing risk assessments and traditional toxicity tests do not incorporate sublethal effects. Because EE2 and FLX have the potential to alter serotonin, dopamine, and estrogenic hormones, biological activities encompassing these chemicals could be affected such as changes in behavior, growth and development, and fecundity. Observations on exposed organisms indicate that there were sublethal effects. The observed increases in abnormal behaviors of exposed organisms included unresponsiveness, irregular swim patterns, erratic activity, and convulsions with observed decreases in feeding habits and aggression. Ethinyl estradiol appeared to accelerate maturation; elevated concentrations appeared to slightly stimulate maturity while appearing to inhibit molting. The organisms exposed to higher concentrations of EE2 and FLX seemed to lack pigment. Continuous environmental pollution of these unregulated chemicals can cause stress on aquatic ecosystems and result in disturbances of the normal development and life cycles of aquatic organisms. If these sublethal disruptions in biological activity continually disregarded, catastrophic destructions of entire ecosystems could transpire.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Walsh, Maud