Assessment of water quality and ecosystem techniques to monitor the environmental effects of salmon aquaculture

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University of New Brunswick
Integrated Multi-Trophic Aquaculture (IMTA) diversifies species culture to produce a variety of products and mitigate nutrient impacts associated with finfish culture. This study examined two biological indicators that could be used to assess IMTA performance with respect to changes in nutrient release. Changes in biocolonization of wild fouling species were examined as an indicator of organic nutrients. Bio-collectors were deployed at different distances from finfish sites to determine if differences in the accumulation of fouling species could be used to detect an aquaculture nutrient source. Biomass accumulation was different with respect to distance from farms and it appears that changes in species composition is responsible. Although there were no measurable differences with respect to distance from salmon cages in environmental conditions such as temperature, salinity, pH, turbidity or chlorophyll, further investigation is suggested to better understand the role of site infrastructure. The relationship between algal colour (lightness, chroma, hue) and nitrogen content within Ulva lactuca, Palmaria palmata, and Poryphyra purpurea was also examined as an indicator of inorganic nutrients. Within each species, colour change corresponded to nitrogen concentration in the thallus, but season and location were significant factors. Palmaria palmata and P. purpurea exhibit less predictable relationships between colour and nitrogen and are harder to identify than U. lactuca and would not be reliable indicators at certain times of year or locations. In both studies the use of wild species responses to nutrient availability was influenced by species type and variability in the coastal environment and require further study before application as tools for IMTA performance monitoring and assessment.