Introduction
Aquaculture is one of the fastest-growing food production sectors, but it also faces increasing scrutiny due to its environmental impact—particularly the high carbon footprint associated with aquafeed production. As the demand for seafood rises, there is an urgent need to reduce the industry’s environmental burden by identifying low-carbon or carbon-neutral alternatives to conventional feed ingredients. One promising yet underutilized solution lies in the use of materials derived from Integrated Multi-Trophic Aquaculture (IMTA) systems (Rusco et al., 2024). These systems produce nutrient-rich by-products that can be repurposed as sustainable feed ingredients, turning waste into value while closing resource loops (Masi et al., 2024). The utilization of IMTA-derived ingredients not only helps lower the carbon footprint of aquafeed but also supports a broader transition toward a more circular, resilient, and eco-friendly aquaculture industry. Among the most promising IMTA-derived candidates for sustainable feed are species such as polychaetes and seaweed, which offer both nutritional value and carbon mitigation potential:
· Polychaetes (Sabella spallanzanii): A carbon-sinking polychaetes species cultivated in IMTA on long lines (Arduini et al., 2023).
· Seaweed (Ulva lactuca.): commonly used as a “biofilter” in IMTA and reach in protein and lipids, widely utilized as aquafeed ingredients (Shpigel et al., 2017):
This study investigates the potential of incorporating these IMTA produced ingredients into the diet of juvenile seabass (Dicentrarchus labrax), aiming to supports the development of circular food systems that can enhance the resilience and economic viability of aquaculture operations.
Materials and Methods
This trial was conducted at the Laboratory of Aquaculture, Department of Veterinary Medical Sciences, University of Bologna (Cesenatico, Italy). Juvenile seabass (Dicentrarchus labrax; initial average weight 5 ± 2 g) were sourced from Panittica Italia and acclimated for two weeks. Fish (n= 100/tank) were randomly stocked into nine 450 L square tanks (three replicates per dietary treatment) and reared for ~30 days. Tanks operated within a closed recirculating aquaculture system (RAS) equipped with mechanical sand filtration, ultraviolet lights, and a biofiltration as described by Parma et al. (2023). Water parameters were maintained at 24 ± 1.0 °C, 25 ± 5.0 g/L salinity and oxygen levels at 8.0 ± 1.0 mg/L using a liquid oxygen system. Feed was produced at the University of Almeria and the ingredients have been directly collected by an experimental IMTA plan located at Marina Grande (Taranto). Fish were fed 4 different pelleted isoproteic and isolipidic diets:
Feeding was performed to satiation with a 10% surplus twice daily (8:30 and 16:30) six days per week. At the beginning and end of the experiment, all fish are anesthetized or euthanized with tricaine methanesulfonate (MS-222). Growth performance and whole-body and dietary proximate analyses parameters are calculated. Gene expression related to digestion (amyl, lip and pept), appetite (pomc a, ghrl, cart), growth (gh, igf1, oxidative stress (sod and cat), immune related genes (il1β and il10) and physiological stress (hsp70 and hsp90) are analyzed to evaluate the nutritional and physiological response to the different diets. All experimental procedures were approved by the Ethical Scientific Committee for Animal Experimentation of the University of Bologna (ID 113/2020-PR), following European Directive 2010/63/EU.
Results and Discussion
Preliminary results suggest that the inclusion of Sabella spallanzanii and Ulva lactuca in the diet for juvenile seabass do not have negative effects on growth performance and biochemical composition of fish. This is because both Sabella meal And Ulva meal are rich in high-quality proteins containing essential amino acids required for growth and development, and these proteins are highly digestible. Furthermore, an increase in feed intake (FI) and the expression of genes related to appetite regulation (ghrl and pomca) is observed due to the known high palatability of Sabella spp. Additionally, Sabella spp. as well as Ulva contain bioactive compounds such as peptides and polysaccharides that have immune-boosting properties, as observed from the upregulated expression of il10 and reduced hsp70. However, large-scale production and harvesting of Sabella spp. may involve high costs, potentially impacting the feasibility of its inclusion in commercial aquafeeds. Despite these challenges, when properly managed, dried Sabella meal in combination with Ulva meal can promote growth, enhance feed palatability, and boost immunity due to their superior protein quality, beneficial lipids, and rich mineral content.
Reference
Arduini, D.; Calabrese, C.; Borghese, J.; De Domenico, S.; Putignano, M.; Toso, A.; Gravili, C.; Giangrande, A. Perspectives for Exploitation of Sabella spallanzanii’s Biomass as a New Integrated Multi-Trophic Aquaculture (IMTA) By-Product: Feeding Trial on Amphiprion ocellaris Using Sabella Meal. J. Mar. Sci. Eng. 2023, 11, 123. https://doi.org/10.3390/ jmse11010123
Masi, M.; Adinolfi, F.; Vecchio, Y.; Agnusdei, G.P.; Coluccia, B. Toward the Circular Economy in the Aquaculture Sector: Bibliometric, Network and Content Analyses. Sustainability 2024, 16, 5405. https:// doi.org/10.3390/su16135405
Rusco, G.; Roncarati, A.; Di Iorio, M.; Cariglia, M.; Longo, C.; Iaffaldano, N. Can IMTA System Improve the Productivity and Quality Traits of Aquatic Organisms Produced at Different Trophic Levels? The Benefits of IMTA—Not Only for the Ecosystem. Biology 2024, 13, 946. https://doi.org/10.3390/biology13110946
Shpigel, M., Guttman, L., Shauli, L., Odintsov, V., Ben-Ezra, D. and Harpaz, S., 2017. Ulva lactuca from an integrated multi-trophic aquaculture (IMTA) biofilter system as a protein supplement in gilthead seabream (Sparus aurata) diet. Aquaculture, 481, pp.112-118.