The aquaculture sector is essential for food security, but its sustainable development depends on the efficient use of resources and the reduction of environmental impact. To ensure the sustainable growth of this vital sector, innovative solutions such as recirculating aquaculture systems (RAS), enabled by advancements in engineering design and monitoring technologies, are gaining global traction among investors and fish farms. RAS facilities are typically land-based super-intensive production systems that rely on advanced filtration and life marine species. In response to these environmental challenges, the AQUA4ALL project aims to close the water and nutrient cycle in RAS systems through a circular economy approach, promoting a more sustainable aquaculture sector and improving the ecological status of surrounding marine environments.
Water samples were collected from four RAS systems: rotifers, turbot (Psetta maxima), sole (Solea senegalensis), and gilthead seabream (Sparus aurata), at multiple system points (rotifers: tank, biofilter, skimmer; turbot and sole: sludge after the drum filter, sludge after the skimmer and the overflow; seabream: effluent after the skimmer and overflow effluent after the biofilter).
Preliminary results revealed distinct bacterial dynamics across species and sampling zones, with notable differences in total marine bacterial load and Vibrionaceae levels, reflecting the influence of system design and biological activity. Microbiological assessment of RAS for rotifers, turbot, sole and seabream revealed distinct bacterial dynamics.
In the rotifer system, the water from the culture tanks showed the highest bacterial load, while the biofilter and skimmer remained stable with low Vibrionaceae levels.
Turbot RAS samples revealed temporal fluctuations, especially in Vibrionaceae.
Sole RAS samples showed microbiological stability, with the highest Vibrionaceae proportion in the drum filter. In the seabream RAS system, bacterial load increased in the skimmer, while Vibrionaceae levels remained stable across sampling points. Distinct bacterial profiles were observed across RAS, with variations in total bacterial load and Vibrionaceae levels influenced by species and system components. The AQUA4ALL project aims to enhance sustainability in aquaculture by closing the water and nutrient cycle in RAS systems through a circular economy approach. By converting nutrient-rich effluents from fish farming into microalgae biomass for industrial use, the project aims to reduce environmental impact, support resource recovery, and foster the development of innovative, eco-friendly products. In essence, this project aims to turn waste into value.
Acknowledgements
AQUA4ALL was supported by Algarve 2030, by Portugal 2030 and by the European Union; Missão Interface, project co-funded by PRR - Plano de Recuperação e Resiliência pela União Europeia (operation code 01/C05-i02/2022.P148) and SAUDE&AQUA-II (MAR-021.1.3-FEAMPA-00018).