Pharmaceuticals and personal care products are a contaminant class of emerging concern, detected in waters worldwide. The notable non-lethal environmental prevalence of pharmaceuticals could indicate they may be a potential source of global change. While the ecotoxicology is understood, ecosystem-scale impacts at non-lethal levels have not been fully explored. We used stream biofilm communities to assess ecosystem response. Biofilms were cultivated on tiles in streams of the Huron River watershed and exposed to triclosan, diphenhydramine, and sulfamethoxazole-trimethoprim treatments for microcosm experiments. Chlorophyll fluorescence and microbial community analysis ecoplates showed no difference in response between treatments and controls. DOC consumption decreased across all sites except Mill Creek by an average of 5.7%, 4.8%, and 1.7% in urban biofilms and 3.7%, 4.3%, and 2.8% in agricultural and natural biofilms when exposed to triclosan, diphenhydramine, and sulfamethoxazole-trimethoprim, respectively. DNA results showed changes in bacterial communities following exposure to treatments, most notably in response to triclosan and diphenhydramine. Decomposition decreased by an average of 49% in Millers Creek and 30% in Mill Creek when exposed to triclosan. These results indicate that trace pharmaceutical exposure decreases some, but not all, biofilm processes and may impact community composition. Contrary to expectations, the largest impacts were observed in urban sites, indicating these communities may be more susceptible to pharmaceutical inputs. Further research is needed to assess the ecosystem-scale effects of these bioactive pollutants on natural processes in order to better inform regulation regarding our waterways.

Additional Contributors: Dr. Kristin Judd; Dr. Steven Francoeur