Mattrygghet: Integrated Multitrophic Aquaculture for Sustainable and Safe Food Production

The SAFER-IMTA project draws on key expertise from Norway (Møreforsking AS, MF) and China (Institute of Hydrobiology, IHB, Shenzhen University, SZU) to address the need for a more sustainable and safe aquaculture food production. The project aims to develop advanced land-based systems for the culture of lower trophic species (microalgae, macroalgae and sea cucumber) utilizing both particulate and liquid fractions from carp (China) and salmon (Norway) aquaculture effluents. At SZU, anaerobic (AN), facultative anaerobic (FA) and aerobic (AE) digestions of solid aquaculture sludge were evaluated for nutrient recovery efficiency and suitability for subsequent cultivation of the green microalga Chlorella sorokiniana. AN resulted in the highest values of maximum dissolved total nitrogen (82.7 mg L-1) and total ammonia (83.9 mg L-1) while AE exhibited highest values of maximum total phosphorus (11.8 mg L-1) and total suspended solid reduction (36%). Microbial analysis showed that AN exhibited a distinct bacterial community composition compared to FA and AE. C. sorokiniana grown in effluents from AN for 12 days exhibited highest biomass production (1.96 g L-1), and highest removal efficiencies of organic matter (78.3%) and dissolved total N (82.5%), suggesting that AN has the best potential to recover nutrients from aquaculture sludge for production of C. sorokiniana. At IHB, the effects of light qualities (white, red, blue, different ratios of red and blue) were investigated on C. sorokiniana cultivated in aquaculture wastewater. The results showed that white light promoted growth and resulted in the highest algal dry weight (DW) of 1.64 g L-1, highest biomass productivity of 0.19 g L-1 d-1. The highest content of protein (21.54% DW), fatty acids (13.56% DW), and removal of total organic carbon (82.27%) and various organic compounds (i.e. microbial byproduct-like aromatic protein) were observed under blue light. Red light promoted C. sorokiniana to accumulate the highest carbon (556.99 mg L-1) and carbohydrates (55.67% DW). In addition, mixed red and blue lights were beneficial for the removal of TN and NH3-N, consumed by non-microalgal pathways. C. sorokiniana was also cultivated in an open raceway on the wastewater from an intensive recirculating aquaculture system (RAS) farm for gibel carp (Carassius gibelio). DIC and DTC gradually decreased by 80.6% and 16.5%, respectively, whereas DOC increased by 52.2%. The removal rates of NH4-N, DTN, DIP and DTP were 93.5%, 86.8%, 36.0% and 26.6%, respectively. The heavy metals and antibiotics contents of C. sorokiniana were conformed to the aquatic feed ingredient standards requirements. ARA, EPA and total PUFAs contents in C. sorokiniana were 13.67, 33.82 and 76.81% of the total fatty acids content. The algae biomass was harvested on Day 7, freeze-dried and supplemented at 0 %, 5% or 15% in the fish feed to replace the fishmeal. The algae did not affect the growth of the gibel carp nor the muscular amino acids contents, but promoted the body colour of the fish and the relative muscular content of n-3 PUFAs. 5% C. sorokiniana in the diet upregulated the relative expression of catalase and increase its activity in the liver; upregulate the relative expression of the proinflammatory factor and the anti-inflammatory factors; and reduce the relative abundance of pathogenic bacteria in the fish gut. Overall, C. sorokiniana has the ability to remove nutrients from aquaculture wastewater and can be an alternative protein source for fish. At MF, particulate sludge from Atlantic salmon aquaculture was assessed as an ingredient for aquaculture feeds for red sea cucumber (Parastichopus tremulus). Four groups consisting of triplicate of 5 individuals (average initial biomass 524.6 ± 12.9 g), were fed at a weekly rate of 10% (wet weight). Feeds were prepared using Sargassum sp., dried sludge collected at 2 different times of the year, and sludge anaerobically fermented with lactic acid bacteria (LAB) at SZU. Feed intake was significantly higher for the control feed, whereas there was no significant difference between the three sludge-based feeds. However, feed intake decreased throughout the experimental period for all feeds. At the end of the trial, all groups had lost weight (final biomass 421.0 ± 50.7 g), and no weight difference was found between the groups. Body wall (gutted weight), presence of intestine and gonad tissue was also assessed. The group fed fermented sludge had a significantly higher gonad index. The content of harmful compounds in the feed were found to be within recommended limits, and sea cucumber body wall was safe for human consumption. Finally, analyses are ongoing to understand what types of information are needed for the decision makers to develop an adapted legislation to guide the sustainable and safe development of feed and food products by an innovative IMTA industry.

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The global aquaculture sector is expected to grow to feed an increasing world population. Yet, the industry’s relies on limited and unsustainable sources of raw materials for aquafeed production. Additionally, nutrient-rich aquaculture effluents represent an underutilized resource with rising environmental concern. SAFER-IMTA draws on key expertise from Norway (Møreforsking AS) and China (Institute of Hydrobiology, Shenzhen University) to address the need for a more sustainable and safe aquaculture food production. The consortium will build upon existing knowledge to demonstrate the concept of integrated multi-trophic aquaculture (IMTA) to maximize resource utilization and limit environmental impacts from fed aquaculture. The project aims to develop advanced land-based systems for the co-culture of lower trophic species (microalgae, macroalgae and sea cucumber) using both particulate and liquid fractions from carp (China) and salmon (Norway) aquaculture. Biological processes coupled to physical and/or chemical processes will be investigated to convert the waste fractions to suitable substrates for sea cucumber and algal production. The safety and quality of lower trophic products in the perspective of their use as food and aquafeed ingredients will be assessed based on their characterization for harmful compounds (e.g. heavy metals, dioxins, PCBs) and essential nutrients (e.g. proteins, lipids, minerals). Life cycle assessments will provide important information on the environmental footprint of the developed systems. The knowledge generated by the consortium will bring the IMTA production technology further and increase the understanding of societal impacts of its processes and products though stakeholder consultation and regulations surveys. Better understanding of the incentives and barriers for the implementation of IMTA systems along with technological innovation will contribute to the development of sustainable value-chains in the aquaculture sector.