Abstract
Integrated multitrophic aquaculture (IMTA) is a versatile technology emerging as an ecological and sustainable solution for traditional monoculture aquacultures in terms of effluent treatment. Nevertheless, IMTA is still poorly applied in aquaculture industry due to, among other reasons, the lack of effective, low-investment and low-maintenance solutions. In this study, one has developed a practical and low maintenance IMTA-pilot system, settled in a semi-intensive coastal aquaculture. The optimisation and performance of the system was validated using Ulva spp., a macroalgae that naturally grows in the fishponds of the local aquaculture. Several cultivation experiments were performed at lab-scale and in the IMTA-pilot system, in static mode. The specific growth rate (SGR), yield, nutrient removal, N and C enrichment, protein and pigment content were monitored. Ulva spp. successfully thrived in effluent from the fish species sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) production tanks and significantly reduced inorganic nutrient load in the effluent, particularly, NH4+, PO43− and NO3−. The enrichment of nitrogen in Ulva spp.’s tissues indicated nitrogen assimilation by the algae, though, the cultivated Ulva spp. showed lower amounts of protein and pigments in comparison to the wild type. This study indicates that the designed IMTA-pilot system is an efficient solution for fish effluent treatment and Ulva spp., a suitable effluent remediator.
Highlights
Aquaculture is an important economic sector growing worldwide to meet the current demand of fish consumption [1]
Our aim was to develop a solution for coastal aquacultures, with the least impact possible to the aquaculture’s normal functioning, that enables the treatment of their effluents before discharge, reducing the anthropogenic pressure on estuarine and coastal ecosystems, and ensuring compliance with the current laws and regulations
Its performance and suitability as a sustainable solution of effluent-treatment for coastal aquacultures was first validated with Ulva spp., as this macroalgae naturally grows in the aquaculture tanks
Summary
Aquaculture is an important economic sector growing worldwide to meet the current demand of fish consumption [1]. The gross investment on this area has been mostly on infrastructures to effectively increase production, that is to grow more fish per area [3,4], while ensuring product quality. Aquaculture productions worldwide produce effluents enriched with nutrients and suspended solids derived from the remains of uneaten feed and waste from fish metabolisms [5]. The discharge of these nutrient-rich effluents into the aquatic environment can cause harmful effects in these ecosystems, such as eutrophication [1,6,7]. European directives promote greener and sustainable processes [1,8,9], aiming at protecting aquatic ecosystems, the treatment of fish effluent is still quite disregarded
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