The Effectiveness of Microbial Filter in Recirculating Aquaculture System

Aquaculture Engineering

Aquaculture production accounts for nearly 50% of fish produced for consumption, estimates suggest a five-fold increase in production is required to meet the protein needs of the community. However, increasing production will also increase the negative impact on the environment. Recirculating Aquaculture Systems (RAS) is a fishery production system that reprocesses water used to meet water quality requirements for aquaculture activities. The diversity of RAS-filtering microbial communities in freshwater and marine systems is based on studies using 16S rRNA and functional gene-specific probes or 16S rRNA gene libraries rather than culture-based techniques. Aquaculture systems rely on nitrification to convert toxic ammonia to nitrite and then nitrate, to prevent the accumulation of potentially toxic or harmful forms of nitrogen (non-ionized ammonia, nitrite). Nitrification is accomplished using biofiltration. Several phylotypes of 16S rRNA genes associated with heterotroph denitrification, including Pseudomonas sp., Aqua spirillum sp., and a wide variety of A-Proteobacteria, were found in the anaerobic nitrate-stimulated enrichment derived from the marine RAS nitrate community, possibly contributing to the nitrate-reducing activity. The results obtained demonstrated that nitrifying microorganisms in RAS are different from those used traditionally to model the nitrifying capacity of RAS. Some researchers have hypothesized that each RAS biofilter should have a different composition of the microbial community formed by the operational controls and components implemented in the RAS.

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