Antifouling agents in aquaculture: A study on the bioaccumulation and effects of copper and tralopyril in blue mussels in a laboratory experiment.

Abstract

Biofouling of net pens from open fish farms is of concern to Norwegian finfish farming and aquaculture industry due to its negative effects on stock, equipment, and infrastructure. A high flow-through of oxygen rich water is needed to ensure a sellable high-quality product, and antifouling biocides are widely used to achieve this. Historically, copper based antifoulants have been the most used antifoulant in Norwegian aquaculture. Although, the use of copper as an antifoulant can be disadvantageous due to relatively low efficacy, accumulation in sediments posing the threat of relocation, and the well-known toxic effects of copper to non-target species. Novel antifoulants such as tralopyril is being marketed as a metal-free alternative with a short half-life and, according to the manufacturer of Econea (a tralopyril based antifoulant), degrades to low toxicity daughter compounds. The aims of this thesis were to investigate and compare uptake, bioaccumulation, and physiological effects of exposure to copper and tralopyril in blue mussels. Mussels are both a fouling species, a widely used bioindicator species and a key species in coastal ecosystems. In this study we exposed blue mussels to increasing concentrations of copper and tralopyril in “pulses” of 1- and 24- hours. Following exposure, mortality was noted, and sub-lethal effects were assessed by investigating bioaccumulation in blue mussel tissue, histological analyses of digestive tubules and gills, and the rate of oxygen metabolism. As an addition to this thesis we detected and quantified a transformation product of tralopyril (HTFCCP) in our samples and investigated its stability relative to tralopyril and its bioaccumulation in blue mussels. In conclusion, the results indicate that tralopyril is a more potent antifouling biocide for adult blue mussels when compared to copper. This is based on observations of similar sub-lethal effects and mortality at lower concentrations of tralopyril. The nature and properties of transformation products must be investigated further.