Evaluation of the potential for trophic transfer of roxithromycin along an experimental food chain.

Pharmaceuticals have been recognized as a new class of environmental pollutants in recent years. But data about their potential for transfer and biomagnification in aquatic food chains are still lacking. In this study, bioaccumulation of the macrolide antibiotic roxithromycin (ROX) was determined in an experimental aquatic food chain involving the green algae Scenedesmus obliquus, the water flea Daphnia magna and the crucian carp Carassius auratus. After 48 h of exposure, S. obliquus accumulated ROX from media, with bioconcentration factors (BCFs) of 74.6, 46.3, and 24.5 l kg(-1) at nominal exposure concentrations of 4, 20, and 100 μg l(-1), respectively. After 48 h of feeding ROX-contaminated algae, D. magna was able to accumulate ROX in all three concentration treatments, but biomagnification did not occur at this trophic level, as biomagnification factors (BMFs) varied from 0.21 to 0.29 in different concentration treatments were well below one. In tissues (muscle, gill, liver, and bile) of C. auratus fed with contaminated daphnia for 8 days, no biomagnification was observed. However, this species did accumulate a certain degree of ROX through food chain transfer, and the tissue burden was greatest in the liver > muscle > gill and lowest in the bile. This work suggests that the trophic transfer should be a matter of concern for ecological risk assessments of pharmaceutical substances in aquatic food webs.