Organic solvents alter photophysiological and oxidative stress profiles of the coral Zoanthus sp.-Towards an optimization of ecotoxicological protocols

Coral reefs are declining, affected by climate change and escalating anthropogenic pressures, such as pollution or habitat alteration. Consequently, ecotoxicological assays with tropical corals have increased, specifically towards the study of emergent or persistent pollutants. However, standardized methodology to test for corals is non-existent, and their response to organic solvents, recurrently required in ecotoxicological appraisals, remains unknown. Therefore, we aimed to establish a threshold for the safe use of the selected solvents in ecotoxicological studies with these organisms. We assessed the oxidative stress response (antioxidant response and oxidative damage), cellular energy allocation and photophysiology of the photosynthetic coral Zoanthus sp. (Anthozoa, Hexacorallia) exposed to six doses of three different organic solvents (ethanol, methanol and dimethyl sulfoxide - DMSO). Our results suggest that the coral is more sensitive to methanol and DMSO than to ethanol. Methanol and DMSO LOEC were 0.01 mL L-1 affecting maximum quantum yield (F-v/F-m) and glutathione S-transferase (GST) activity, respectively, while for ethanol was 0.03 mL L-1, influencing F-v/F-m. Despite the higher tolerance of Zoanthus sp. to ethanol, 2.9 mL L-1 of this organic solvent was the only treatment causing mortality. Based on these findings, thresholds for the use of organic solvents with tropical corals can now be adopted. Nevertheless, species specificities should not be overlooked. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Coral reefs are declining due to climate change and increasing anthropogenic pressures. Standardized methodology for ecotoxicological studies with corals is lacking, and establishing thresholds for the safe use of organic solvents is crucial. The sensitivity of coral species to different organic solvents should be taken into consideration for research and conservation efforts.