Résumé
As part of the All-Atlantic Ocean Sustainable, Profitable and Resilient Aquaculture (ASTRAL) project, we have investigated the benefits of growing the green seaweed Ulva lacinulata in land-based, partiallyrecirculated aquaculture systems with either abalone, Haliotis midae or sea urchin, Tripneustes gratilla. We demonstrated that integrated multitrophic aquaculture (IMTA) grown Ulva is an excellent source ofminerals, vitamins, AA's, FA's, protein, complex polysaccharides, and other bioactive compounds. When used as a feed or a feed component, Ulva enhanced the chemosensory properties of formulated feedsand significantly improved feed consumption, reducing reliance on harvesting of natural seaweeds and dependence on the use of protein-rich formulated feeds. The nutrient uptake efficiency of Ulva wasshown to be ~60% in the abalone-Ulva IMTA with 50% recirculation, and ~80% in the urchin-Ulva IMTA with 90% recirculation. When recirculation rates were increased from 0-50% for the abalone and 0-90%for the urchin IMTA systems, energy consumption was reduced from 10.35-6.80 kWh per ton abalone and 12.45-3.54 kWh per ton urchin biomass harvested. A perceived risk of growing Ulva in abaloneeffluent and utilizing it as a supplementary feed is biosecurity. However, our comprehensive microbiome studies have revealed high microbial diversity in all compartments of the IMTA, indicative of a healthy system,and Ulva exhibited a modulatory effect on the microbiome, reducing the abundance of opportunistic pathogens (e.g., Vibrio spp.). Collectively, our studies revealed several benefits associated with the cultivation of Ulvain IMTA systems and high potential for IMTA to support sustainable aquaculture and a circular bioeconomy