Ecotoxicological implications of hydrogen peroxide environmental discharge on marine invertebrate organisms

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Chemical contaminants can enter coastal marine systems by various sources including discharge through waste water systems, land run-off, and coastal industrial activities such as aquaculture. Organisms in the coastal marine environment are exposed to a wide range of pollutants and contaminants, and understanding mechanisms of toxicological effects of exposure is essential for assessing potential long-term impacts on populations and ecosystems. This project seeks to focus on key contaminants of current relevance in Scottish coastal environment, for example contaminants entering the marine environment from waste water treatments or industrial activities such as coastal aquaculture. Salmon farming has seen a rapid increase in Scotland over the last twenty years, with clear indications of investment and growth continuing in the years to come. Hydrogen peroxide will be the main target contaminant due to its use as a biofouling treatment on submarine structures and as a chemical treatment of sealice in marine salmon farming facilities. Of particular focus will be effects on sea urchins and mussels due to their ecological roles as benthic detritivores and filter feeders as well as their economic value as potential target fisheries. There is a current interest in Scotland to develop integrated multi-trophic aquaculture (IMTA) for sustainable, efficient, and productive development of the aquaculture industry, and both sea urchins and mussels are considered for development in IMTA systems. Mussels are of additional interest in the west coast of Scotland due to the productive and growing mussel aquaculture industry. Mussel farms are co-located in the same sea loch systems with salmon farms; therefore, it is of particular interest to understand the toxicological impacts of inadvertent exposure to chemical discharges from salmon farms.Hydrogen peroxide sealice treatment is being used more frequently due to the fast reactivity and breakdown in the environment and the absence of bioaccumulation that is evident with some alternative chemical treatment options (e.g. emamectin). Hydrogen peroxide produces reactive oxygen species and can cause oxidative damage in tissues, including DNA strand breaks. There have been reports of non-target effects in crustacean (shrimp) populations near salmon pens in Norway. It is unknown how and to what extent the concentrations and environmental exposure resulting from treatment of a coastal salmon aquaculture facility can impact organisms in the surrounding water. Both sea urchins and mussels are well-established model organisms in ecotoxicological studies, with fully sequenced and annotated genomes providing genetic and molecular tools for research, in the context of well-characterised physiology, behaviour, and reproduction. They are widely used as bioindicators for the presence of water-borne environmental contaminants, and biomarker analyses are well described and optimized. The scientific approach will be to investigate toxicological effects of environmentally relevant exposures of sea urchins and mussels to hydrogen peroxide. These experiments will characterise reproductive and developmental toxicity, and involve both adult and larval exposures.