Pharmaceuticals are recognised contaminants of concern in aquatic ecosystems and are often detected in surface waters receiving wastewater, at ng/L concentrations. Studies are beginning to examine the influences of pharmaceuticals on a range of ecosystem metrics, including algal primary production and invertebrate community composition. However, studies examining the response of diatom community composition are lacking.
Here, we present results from three separate studies examining the impacts of different pharmaceuticals at environmentally realistic concentrations on diatom community composition. The first shows that a realistic pharmaceutical cocktail significantly shifted periphyton diatom community composition irrespective of light conditions. The second shows that ng/L concentrations of ciprofloxacin, diphenhydramine and fluoxetine changed diatom community composition only on successional biofilms and not established biofilms, and finally the third study shows that diatom community composition was shifted by exposure to cetirizine and diphenhydramine, and that the magnitude of the community shift was concentration dependent. We show that these results can be context dependent, and that there is potential for diatom community metrics to be used as bioindicators for pharmaceutical contamination. These studies are some of the first to demonstrate that diatom community composition is significantly altered by ng/L concentrations of multiple pharmaceuticals.