Abstract
The discharge of pharmaceuticals via wastewater into the environment is a great concern due to the constant threat posed to photosynthetic organisms since they are vital for the sustenance of the aquatic food web. To compare the photosynthetic and growth responses of green algae to human antibiotics, Raphidocelis subcapitata and Chlorella vulgaris were exposed to erythromycin and sulfamethoxazole for 96 h. A much higher sensitivity was shown by Raphidocelis to the antibiotics. Although erythromycin was more acutely toxic to photosynthesis (EC50, 24.6 μg/L; EC10, 14.6 μg/L) than growth (EC50, 160 μg/L; EC10, 27 μg/L) in Raphidocelis, chronic effects in terms of EC10 were alike. Interestingly, sulfamethoxazole exhibited similar toxicity towards growth and photosynthesis with the acute and chronic toxicity parameters for growth (EC50, >2000 μg/L; EC10, 260 μg/L for Raphidocelis; and EC50, 47,900 μg/L; EC10, 19,100 μg/L for Chlorella) in consonance with those of photosynthesis (EC50, >2000 μg/L; EC10, 340 μg/L for Raphidocelis; and EC50, 47,500 μg/L; EC10, 13,400 μg/L for Chlorella). Growth and photosynthesis in Raphidocelis were strongly inhibited in this study at environmentally relevant concentrations of erythromycin. The findings from this study demonstrated that photosynthetic yield was a reliable indicator of sulfamethoxazole and erythromycin effects and thus, may be useful as an alternative approach to growth in assessing chronic toxicity in antibiotics.
Highlights
The findings from this study demonstrated that photosynthetic yield was a reliable indicator of sulfamethoxazole and erythromycin effects and may be useful as an alternative approach to growth in assessing chronic toxicity in antibiotics
There are about 9000 WWTWs that the UK water industry manages [8] and depending on the pharmaceutical, the removal efficiency varies greatly in the generally aerobic processes employed in these treatment plants [9], allowing a percentage of the unaffected parent compound into the environment
ERY was highly toxic to R. subcapitata, strongly inhibiting growth and photosynthesis in this study at environmentally relevant concentrations
Summary
There are about 9000 WWTWs that the UK water industry manages [8] and depending on the pharmaceutical, the removal efficiency varies greatly in the generally aerobic processes employed in these treatment plants [9], allowing a percentage of the unaffected parent compound into the environment. Human pharmaceutical residues in wastewater represent a global threat to non-target aquatic organisms, even at low concentrations, due to their bioactive nature and continuous infusion into the aquatic environment from WWTWs [11]. A recent study commissioned by Centre of Expertise for Waters identified eight pharmaceuticals including two antibiotics as posing a high ecotoxicological risk in Scotland’s inland surface waters [12]
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