Low-level pharmaceuticals alter stream biofilm structure and function

ABSTRACT

Pharmaceuticals and personal care products (PPCPs) are a contaminant class of worldwide concern and a potential source of global change. To better understand the impact of low levels of PPCPs on stream biofilm structure and function, we conducted laboratory mesocosm experiments in which biofilms cultivated in streams draining areas of different land use (natural, agricultural, and urban) were exposed to low levels (5 µg L⁻¹) of several common pharmaceuticals. We performed several functional assays and assessed differences in biofilm bacterial community composition among pharmaceutical treatments and streams. Pharmaceutical treatments altered the functional capacity and diversity of biofilms, but had no significant effect on carbon uptake or photosynthetic potential. Biofilm bacterial communities differed with land use, and pharmaceutical treatments decreased the relative abundances of Alcanivorax and Halioglobus and increased the relative abundance of Pseudomonas, indicating a shift to more drug-tolerant groups. Overall, our results provide evidence that PPCPs may act as ecological disruptors even at low levels, altering biofilm structure and some aspects of ecosystem function, and potentially influencing important biogeochemical processes in streams.

KEYWORDS:

• caffeine
• community level physiological profiling
• diphenhydramine
• PPCPs
• triclosan
• urban streams

Acknowledgements

We thank A. Tanguay for assistance in the field and in the lab, S. Francoeur for help with statistical analyses, and S. Francoeur and D. Clemans for feedback on early manuscript drafts. Parts of the text have been previously published in partial fulfilment of the academic degree (M.S.) for author Elizabeth Stover at Eastern Michigan University (EMU). Funding for this project was provided by awards to E.S. from the EMU Department of Biology, the EMU Graduate School, and the Mill Creek Research Council.

Author contributions

ES, KJ conceived and designed the research; ES carried out the field sampling and laboratory experiments. ES analysed the data; ES, KJ wrote and edited the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Elizabeth M. Stover

Elizabeth M. Stover received her M.S. in Ecology, Evolution, and Organismal Biology at Eastern Michigan University.

Kristin E. Judd

Kristin E. Judd is a Professor of Biology at Eastern Michigan University. Her research interests include aquatic biogeochemistry.