Hydrogen peroxide-induced genotoxicity and transgenerational implications in sea urchins

Abstract

Hydrogen peroxide (H₂O₂) is an antiparasitic treatment against sea lice in Atlantic salmon aquaculture and is released into the surrounding waters. H₂O₂ is presumed to degrade and dilute rapidly within days and considered environmentally friendly. However, modelling studies showed persistence of H₂O₂ up to 1km from release sites. H₂O₂ is a known genotoxicant and this thesis investigates degradation rates and genotoxicity in sea urchins exposed to environmentally-relevant concentrations of H₂O₂. The degradation rate of H₂O₂ was 1% per day, slower than reported in previous studies which suggested limited environmental impact due to rapid breakdown in seawater. Sea urchins were selected as bioindicator species and exposed to environmentally-relevant exposure simulations of pelagic and benthic life stages to H₂O₂. Genotoxicological impacts were assessed in adult coelomocytes and tube feet, gametes, and embryos. The fast micromethod was used to quantify DNA strand breaks in sea urchin coelomocytes, then further developed to include simultaneous quantification of DNA strand breaks, oxidised DNA bases, and methylated cytosines. Interspecies differences in susceptibility to DNA damage were detected in coelomocytes of three Scottish species. Low concentration of H₂O₂ (500μM, 100-times dilution of sea lice treatment) induced DNA damage in coelomocytes from adult aqueous exposures after 1h, but the damage rapidly returned to control levels by 3h. Gametes (eggs and sperm) exposed to H₂O₂ did not impact gamete viability but resulted in reduced fertilisation success and elevated DNA damage in embryos, possibly through sublethal DNA damage maintained through fertilisation and unrepaired in early stages of development. This thesis provides evidence of environmentally-relevant levels of H₂O₂-induced DNA damage in multiple stages in the sea urchin life cycle. Genotoxic evidence in sea urchins calls the need for strict regulations on safe disposal of H₂O₂ and other environmental chemicals to ensure the health of benthic and pelagic ecosystems in the marine environment.

Date of Award	7 Nov 2023
Original language	English
Awarding Institution	University of the Highlands and Islands
Sponsors	Super DTP
Supervisor	Helena Reinardy (Supervisor) & Kim Last (Supervisor)