Pharmaceuticals Poison Water Supply & Aquatic Life

Biofilms – which most people know as the slippery coating on stream rocks – are vital to stream health, housing complex communities composed of algae, fungi, and bacteria all living together. In streams, biofilms contribute to water quality by recycling nutrients and organic matter; they are also a major food source for invertebrates that, in turn, feed larger animals like fish.  Emma Rosi-Marshall, from the Cary Institute of Ecosystem Studies (New York, USA), and colleagues analyzed how six common pharmaceuticals influenced similar-sized streams in New York, Maryland, and Indiana. Caffeine, the antibiotic ciprofloxacin, the antidiabetic metformin, two antihistimines used to treat heartburn (cimetidine and ranitidine), and one antihistamine used to treat allergies (diphenhydramine) were investigated, both alone and in combinations, using pharmaceutical-diffusing substrates.   The most striking result of the study was diphenhydramine's effects on algal production and microbial respiration. Exposure caused biofilms to experience up to a 99% decrease in photosynthesis, as well as significant drops in respiration. Diphenhydramine also caused a change in the bacterial species present in the biofilms, including an increase in a bacterial group known to degrade toxic compounds and a reduction in a group that digests compounds produced by plants and algae.  The other pharmaceuticals investigated also had a measurable effect on biofilm respiration, both alone and in combinations.