Sensitivity of freshwater and marine green algae to three compounds of emerging concern

Abstract

In this study, the toxicity of three compounds of emerging concern (CEC) belonging to different classes [metolachlor (herbicide), erythromycin (antibiotic) and triclosan (antiseptic)], were evaluated and compared using the freshwater alga Pseudokirchneriella subcapitata and the marine alga Dunaliella tertiolecta. Toxicity assays were performed by exposing algal cells, in exponential phase of growth, to the toxicants for 72 h (P. subcapitata) or 96 h (D. tertiolecta). The toxicant concentrations that induced an inhibition of 50% of algal growth (EC50) of P. subcapitata or D. tertiolecta were 118 and 11.3 × 103 μg L−1 for metolachlor (MTC), 38 and 5.75 × 103 μg L−1 for erythromycin (ERT) and 27.1 and 93 μg L−1 for triclosan (TCS), respectively. Based on these EC50 values, it was possible to hierarchize (decreasing order) the toxicity of the CEC studied: TCS > ERT > MTC. The EC50 values achieved for P. subcapitata were between 3.4- and 151-fold lower than those observed with D. tertiolecta, which demonstrated the higher sensitivity of the freshwater alga comparatively to the marine alga. All 72 h-EC10 or 72 h-EC50 values determined in this study with P. subcapitata are within the concentration range of these pollutants described in the literature, in ground and surface waters, which underlines the significance of this alga in the ecotoxicity assessment of freshwaters.