Ulva lactuca L. as an inorganic extractive component for Integrated Multi-Trophic Aquaculture in British Columbia: An analysis of potentialities and pitfalls




Sherrington, Nicholas Alexander

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Ulva as an aquaculture crop and IMTA component species has received mixed results globally; success has been achieved in South Africa and Israel, whilst in Europe the results have been poor. This project aims to determine if Ulva lactuca is a suitable candidate as an inorganic extractive species component within marine IMTA systems in British Columbia. The inorganic extractive feasibility of U. lactuca was determined with combination of real time growth and nutrient uptake experiments, alongside a SWOT analysis and literature review to reveal the possible potentialities and pitfalls. U. lactuca was cultivated in 680 litre tanks in the effluent of Wolf Eels, Anarrhichthys ocellatus in a recirculation system at the Aquatics facility at the University of Victoria. Growth experiments of wild local U. lactuca strains attained summer growth of up to 17.43% specific daily growth rate, with winter growth of up to 4.26% specific daily growth rate. U. lactuca demonstrates a preference for Ammonia-N uptake over other forms of inorganic nitrogen and a reduced nutrient uptake capacity during dark periods. Nitrate uptake capacity up to 202µm N gDW-1 day-1 was exhibited. These figures display the excellent biological potential of local Ulva lactuca strains to act as an inorganic extractive. However currently, long term maintenance of the crop proved problematic with instability with growth rates and nutrient uptake capacity. Cultivation issues in combination with poor economic outlook will restrict the feasibility of this species to specific types of IMTA system. Beneficial steps towards the deployment of U. lactuca inorganic extractive components would include: (i) the identification of suitable sterile strains or employment of “germling” spore production, (ii) the use of a rotational, light weight, cage cultivation system, (iii) being farmed in combination with a dark period nutrient removal species, such as Chondrus crispus, (iv) being farmed in conjunction with in-situ algivorous species.



Ulva lactuca, Aquaculture, Seaweed, IMTA, Integrated Multi Trophic Aquaculture