Study of water quality in a recirculating aquaculture system for environmental sustainability and fish welfare

Recirculating aquaculture systems (RAS) are a promising technology of fish production to reduce aquaculture environmental impact. Water recirculation relies on the stability of physical, chemical and biological processes to increase biosecurity. Although, disruptions in RAS systems can cause fish disease outbreaks by opportunistic pathogenic bacteria with an economic impact. The aim of this study was to characterize the water microbiota across the different sectors of a flatfish (Solea senegalensis) RAS unit, and understand its relation with the water quality parameters. Analysis was focused on the beneficial microbial community for a better environmental sustainability, but also on the opportunistic agents that threaten the fish welfare. Water samples were collected from four sectors at different filtration stages. For microbial diversity, DNA was extracted from the water samples, sequenced by Illumina MiSeq® and sequences output analyzed by SilvaNGS. Results show that Proteobacteria and Bacteroidetes were the most abundant phyla, and potential pathogenic bacteria were detected. They also indicate that salinity shifts can affect the structure of the bacterial community.