Comparing the sensitivity of chlorophytes, cyanobacteria and diatoms to major-use antibiotics

The occurrence of antibiotic residues in the aquatic environment is an emerging concern. In contrast to daphnia and fish, algae are known to be particularly sensitive to antibiotic exposure. However, to date, a systematic evaluation of the sensitivity of different algal species to antibiotics has not been performed. The aim of the present study was therefore to explore the sensitivity of a battery of algal species towards antibiotic exposures. The present study investigated the growth inhibition effects of three major-use antibiotics, tylosin, lincomycin and trimethoprim, on seven algal species from the chlorophyte, cyanobacteria and diatom groups. Based on EC50 values, cyanobacteria (EC50 = 0.095-0.13 µmol/L) were found to be the most sensitive group to lincomycin followed by chlorophytes (EC50 = 7.36-225.73 µmol/L) and diatoms (EC50 >225.73 µmol/L). Cyanobacteria were also the most sensitive group to tylosin (EC50 = 0.09-0.092 µmol/L) but, for this compound, diatoms (EC50 = 1.33-5.7 µmol/L) were more sensitive than chlorophytes (EC50 = 4.14-81.2 µmol/L). Diatoms were most sensitive to trimethoprim (EC50 = 7.36-74.61 µmol/L) followed by cyanobacteria (EC50 = 315.78-344.45 µmol/L) and chlorophytes (EC50 >344.45 µmol/L) for trimethoprim. While the results of our study partly support the current approach to regulatory environmental risk assessment where cyanobacterial species are recommended for use on antibiotic compounds, they indicate that for some antibiotics this group might not be the most appropriate test organism. We would therefore advocate that environmental risk assessments consider data on three algal groups (chlorophytes, cyanobacteria and diatoms) and use test species from these groups that are consistently found to be the most sensitive (Pseudokirchneriella subcapitata, Anabaena flos-aquae and Navicula pelliculosa). This article is protected by copyright. All rights reserved.