Relationships between the psychiatric drug carbamazepine and freshwater macroinvertebrate community structure.

Pharmaceutical pollutants are commonly detected in surface waters and have the potential to affect non-target organisms. However, there is limited understanding of how these emerging contaminants may affect macroinvertebrate communities. The pharmaceutical carbamazepine is ubiquitous in surface waters around the world and is a pollutant of particular concern due to its recalcitrance and toxicity. To better understand the potential effects of carbamazepine on natural macroinvertebrate communities, we related stream macroinvertebrate abundance to carbamazepine concentrations. Macroinvertebrate and water samples were collected from 19 streams in central Indiana in conjunction with other stream physiochemical characteristics. Structural equation modeling (SEM) was used to relate macroinvertebrate richness to carbamazepine concentrations. Macroinvertebrate richness was positively correlated with increasing concentrations of carbamazepine. From the SEM we infer that carbamazepine influences macroinvertebrate richness through indirect pathways linked to Baetidae abundance. Baetidae abundance influenced ephemeropteran abundance and FBOM percent organic matter, both of which altered macroinvertebrate richness. The pharmaceutical carbamazepine may alter freshwater macroinvertebrate species composition, which could have significant consequences to ecosystem processes.