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

Abstract

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 toward antibiotic exposures. The present study investigated the growth inhibition effects of 3 major-use antibiotics, tylosin, lincomycin, and trimethoprim, on 7 algal species from the chlorophyte, cyanobacteria, and diatom groups. Based on median effective concentration (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. Although these results partly support the current approach to regulatory environmental risk assessment (whereby cyanobacterial species are recommended for use with antibiotic compounds), they indicate that for some antibiotics this group might not be the most appropriate test organism. It is therefore suggested that environmental risk assessments consider data on 3 algal groups (chlorophytes, cyanobacteria, and diatoms) and use test species from these groups, which are consistently found to be the most sensitive (Pseudokirchneriella subcapitata, Anabaena flos-aquae, and Navicula pelliculosa). Environ Toxicol Chem 2016;35:2587-2596. © 2016 SETAC.

Assessment of the Risks of the Major Use Antibiotics in China's Surface Waters Using a Probabilistic Approach

“…Based on the effects on algae, 2 HC5s of 3695 µg/L and 1.22 µg/L were separately derived for trimethoprim and lincomycin (Guo, Selby et al ). In contrast to the 18 610 µg/L and 72.9 µg/L observed in the present study, their results may be too conservative because algal species, in particular cyanobacteria, are more likely to be affected by antibiotics than other aquatic organisms such as fish and crustacea (Guo, Selby et al ). Thus, hazards merely characterized by the effect on algal species may overestimate the ecological risks.…”

Effects of Antibiotics on the Growth and Physiology of Chlorophytes, Cyanobacteria, and a Diatom

“…While SPE was performed to concentrate the exposure solutions for the tests on A. flos-aquae before the algal testing, the volume of solution in the test vial at the end of the study was less than 15 mL so it was not possible to conduct SPE again. While no stability data of the antibiotics for studies with A. flos-aquae during the 4-days period are available, stability data of lincomycin and tylosin have been generated by us in a previous study (Guo et al 2016 ), so these were applied to extrapolate to the intermediate concentration. Data on the stability of the study compounds during the tests on the two chlorophytes and the diatom are presented in Fig.…”

“…Concentrations of the antibiotics in the exposure solutions were confirmed using high performance liquid chromatography (HPLC) using an Agilent 1100 with C18 Supelco Discovery column (15 cm × 4.6 mm × 5 µm). Analytical methodologies were described in detail in Guo et al ( 2016 ). In brief, tylosin and trimethoprim were analysed using a 24-min gradient method.…”

“…Four species, as suggested by the OECD 201 guideline, were studied, including two chlorophytes ( Pseudokirchneriella subcapitata and Desmodesmus subspicatus ), a cyanobacteria ( Anabaena flos-aquae ), and a diatom ( Navicula pelliculosa ). These species previously have been shown to be sensitive to these three antibiotics in a recently sensitivity comparison study (Guo et al 2016 ).…”

“…For example, after exposure to lincomycin, the 3-days median effective concentration values (EC 50 ) for the chlorophyte P. subcapitata was 0.16 µmol L −1 , which is two orders of magnitude lower than effect concentrations for crustacea ( Daphnia magna ) and zebrafish ( Danio rerio) with a 1-day median lethal concentration (LC 50 ) 52.32 µmol L −1 being observed for the daphnids and a 2-days no observed effect concentration (NOEC) of 2257 µmol L −1 being observed for zebrafish (Isidori et al 2005 ). Studies to date into the effects of antibiotics on algae generally have assessed impacts on the growth of a range of algal species and communities (Wilson et al 2003 ; Cleuvers 2003 ; DeLorenzo and Fleming 2008 ; Guo et al 2016 ) using biomass (i.e., cell number) as the endpoint, as suggested by standard bioassay protocols such as the Organisation for Economic Co-operation and Development (OECD 201 guideline) (OECD 2011 ), which includes the standard methods to evaluate the effects of a chemical on the growth of an algal species.…”