| Summary: | I present new knowledge on the toxicity of three major bath treatment chemotherapeutants used in Norway. Previously, regarding the toxicity studies of hydrogen peroxide (H2O2) alone, a total of twelve non-target crustaceans have been examined across the globe, but only five species were relevant for the Norwegian marine ecosystem. The present study applied laboratory experiments to assess the toxicity of this chemotherapeutant to three non-target crustacean species that play a crucial role in the Norwegian marine ecosystem, bringing a better understanding of the risk posed by H2O2. Hydrogen peroxide has long been labeled as the most environmentally friendly bath treatment in use for the salmonid industry. It has also been considered that it poses little to no threat in terms of lethality to non-target crustaceans such as lobster, shrimps or crabs (Burridge et al., 2014; Gebauer et al., 2017). However, papers I, II and III show that the recommended H2O2 concentrations used by the salmonid industry across the globe are lethal to non-target crustaceans. Through the creation of species sensitivity distribution curves (SSD), this thesis identified the Northern krill (Meganyctiphanes norvegica) as the crustacean species that is most sensitive to H2O2 of those that have been tested so far. By including the sensitivity of six phyla other than the arthropods, this thesis takes a broader perspective on the impact of H2O2 on the marine environment. The hazardous concentration of H2O2 for 5% of the species (HC5) derived from the available toxicity data for marine species is 5.11 (1.52 – 16.15) mg/L. As SSD curves are a central tool for ecological risk assessments, showing the different sensitivities and variations between species, it is crucial that this tool continues to be used for the risk assessment of the other chemotherapeutants. Deltamethrin and azamethiphos have a detrimental effect on European lobster larvae (Homarus gammarus) in laboratory experiments (Paper IV). One-hour exposure to deltamethrin proved to be more ...
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