Abstract
AbstractResidues of pharmaceuticals are increasingly detected in surface waters throughout the world. In four streams in Baltimore, Maryland, USA, we detected analgesics, stimulants, antihistamines, and antibiotics using passive organic samplers. We exposed biofilm communities in these streams to the common drugs caffeine, cimetidine, ciprofloxacin, and diphenhydramine. Respiration rates in the least urban stream were suppressed when exposed to these drugs, but biofilm functioning in the most urban stream was resistant to drug exposure. Exposure to the antibiotic ciprofloxacin altered bacterial community composition at all sites, with the greatest change occurring in the most urban stream. These results indicated that continuous exposure to drugs in urban streams may select for sub‐populations of highly resistant bacteria that maintain community function in response to urban contaminants.
Highlights
Microbial biofilms, which are mixed assemblages of microorganisms, that is, bacteria and algae, encased in an extracellular matrix and attached to a surface, are ubiquitous in aquatic habitats and are frequently both structurally and taxonomically complex (Davey and O’Toole 2000)
The abundance of six common drugs was measured in four streams in Baltimore, Maryland, that were known to vary in degree of anthropogenic inputs (Kaushal and Belt 2012)
Sulfamethoxazole, a commonly used antibiotic, was detected at all sites, but the concentrations were higher in the two more urban sites, and the antihistamine diphenhydramine was lower than all other drugs, but was highest at the most urban site
Summary
Microbial biofilms, which are mixed assemblages of microorganisms, that is, bacteria and algae, encased in an extracellular matrix and attached to a surface, are ubiquitous in aquatic habitats and are frequently both structurally and taxonomically complex (Davey and O’Toole 2000). Biofilms are key components of stream ecosystems because they are major drivers of nitrogen and carbon cycling (Battin et al 2003), they are the base of stream food webs (Hall and Meyer 1998, Pusch et al 1998), and they contribute to important ecosystem services, such as decreasing nutrient pollution and bioremediation of organic pollutants (Davey and O’Toole 2000). Continuous exposure to drugs can alter the diversity and taxonomic composition of microbial communities in freshwater ecosystems by selecting for organisms that can tolerate or in some cases digest the contaminant (Drury et al 2013a, Rosi-Marshall et al 2013, Lee et al 2016, Zhang et al 2016). Changes in the diversity and taxonomic composition of stream biofilms may have important implications for the structure and function of these communities and the ecosystem services they provide
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