Pharmaceuticals and personal care products (PPCPs) are contaminants of increasing concern in aquatic ecosystems. PPCPs reach aquatic systems via human waste-water following excretion and incorrect disposal, as well as manufacturing waste and agricultural runoff. Current waste water treatment plants are not equipped to fully remove large organic compounds such as PPCPs, leading to \ frequent detection of PPCPs in surface waters globally. PPCPs pose a considerable risk as an aquatic contaminant as they are biologically active by design, can be taken up by aquatic biota, and have largely unknown effects on non-target organisms including aquatic microbes. Early research indicates that select pharmaceuticals can inhibit functioning of aquatic organisms at low, environmentally relevant concentrations. However, the effects of PPCPs on whole-ecosystem structure and function is largely unknown.
This research examines the effects of a realistic pharmaceutical mixture of eight separate compounds on selected whole-ecosystem endpoints, including primary production, community respiration, microbial biomass and community composition and nitrogen cycling. In addition, we tested whether these effects differed between light and dark (shaded) streams, to test whether differences in energy dynamics driven by light availability alter stream ecosystem responses to pharmaceuticals. .
Artificial streams colonised with rocks, leaf packs and sediment balls which were pre-incubated in a natural stream for one year, one month and one week respectively were divided into both light (unshaded) and dark (shaded) treatments using shade cloth. Within these two groups, half of the streams were dosed every other day with a mixture of pharmaceuticals mirroring those found in an urban North American stream receiving waste water inputs. Effects on biogeochemical processes including primary production, respiration and denitrification were quantified over the entire three week experiment.