Salmon aquaculture-derived nutrients and metals in biota from rocky habitats in the Bay of Fundy
University of New Brunswick
Past studies have assessed the impact of metal and nutrient loading from aquaculture, but few have examined rocky bottom habitats or quantified effects at distances greater than 200 m from salmon pens. My goal was to assess metal contamination and feed reliance at two distances from salmon pens. I deployed 7 bio-collectors at 8 pairs of sites near (68-441 m) and away (260-2750 m) from salmon pen sites across three Bay Management Areas in the Bay of Fundy to assess exposure to copper, zinc and nutrients (using stable isotopes) in five benthic species: blue mussels (Mytilus edulis), vase tunicates (Ciona intestinalis), American lobster (Homarus americanus), shorthorn sculpin (Myoxocephalus scorpius) and rock gunnel (Pholis gunnellus) in 2016 and 2017. Of the combined 41 species-site pair combinations across both years compared using t-tests, 8 and 6 showed significant differences in copper and zinc, respectively, between near and away sites, but the direction of difference was inconsistent. Some species-site pair combinations showed differences in isotope values, but only sulfur isotopes suggested a small shift towards reliance on aquaculture nutrients. Using a chi-square goodness of fit test, only sulfur in 2016 and zinc in 2017 showed significant directionality in the response to being near aquaculture. Overall, my results suggest limited impacts of aquaculture in terms of metal contamination and feed use in animals in rocky bottom habitats greater than 200 m from aquaculture pens.