Integrated multi-trophic aquaculture in a zero-exchange recirculation aquaculture system for marine fish and hydroponic halophyte production

The aim of the study was to investigate the feasibility of nutrient recycling from a marine recirculating aquaculture system (RAS) for fish (European sea bass, Dicentrarchus labrax L.) through three salt-tolerant, halophyte plant species, Tripolium pannonicum (Jacq.) Dobrocz., Plantago coronopus L., and Salicornia dolichostachya (Moss.). Halophytes, illuminated by sunlight and supplemented with artificial light, were maintained in hydroponic cultures integrated in a RAS water treatment system operating at 16 psu salinity. During a 35-day experiment, 248 fishes gained 5.6 kg of weight. Total plant biomass production reached 23 kg in 14 m² hydroponic culture area. Gain of shoot biomass was 27, 18, and 60 g m⁻² day⁻¹ for T. pannonicum, P. coronopus, and S. dolichostachya, respectively. The plants retained 7 g phosphorus and 46 g nitrogen under the experimental conditions. This was equivalent to 9 % of the N and 10 % of the P introduced with the fish feed. The edible part of the harvested plant material was microbially safe and approved for human consumption. The coupling of production in a RAS–IMTA was tested as a feasible cascading production technology for sustainable aquaculture.