Ecotoxicol Environ Saf 2025 Jul 09;302:118631. doi: 10.1016/j.ecoenv.2025.118631.

Environmentally-relevant hydrogen peroxide exposure induces DNA damage and elevates coelomocyte concentrations in the sea urchin Paracentrotus lividus.

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Hydrogen peroxide (H2O2) is an antiparasitic sea lice treatment in Atlantic salmon aquaculture and considered to be environmentally-friendly due to its rapid degradation. However, degradation rates have not been widely tested in seawater. The objectives of this study were to determine the degradation rates of different H2O2 stocks in aquarium-filtered seawater and assess its impact on adult sea urchins (Paracentrotus lividus). H2O2 stocks (stabilised, pure, and industry-sourced EndoSan50) combined degradation rate was 1.92 %/day, and the half-life was 26.4 days. Environmentally-relevant concentrations of H2O2 (50 and 500 µM) were selected for testing. Adult sea urchins were exposed to H2O2 for 3 and 24 h. Total coelomocyte and red cell concentrations increased by 50 ± 22 % and 122 ± 48 %, respectively, after 3 h, and by 59 ± 21 % and 88 ± 44 % after 24 h. DNA damage was analysed by the modified fast micromethod for quantification of strand breaks, oxidised purines (FPG), and oxidised pyrimidines (EndoIII). DNA damage in coelomocytes was increased to 0.05 ± 0.02 strand scission factor (SSF) in sea urchins exposed to 500 µM for 1 h. This study indicates presence of DNA damage in sea urchins from environmentally-relevant concentration of H2O2. Further testing of degradation rates of H2O2 in different sources of natural sea water is required to fully assess and model wider ecosystem exposure and ecological impacts of H2O2 release into coastal marine waters.

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