Effects of biofilter management modalities on the microbiological status in RAS water to avoid recording capacities of biofilms

Abstract

Recirculating Aquaculture Systems (RAS) are increasingly seen as a breeding system of the future. the development of RAS requires understanding the microbial communities, as they play a significant role in the system functioning, water quality and therefore fish welfare and organoleptic characteristics. However, some aspects remain insufficiently explored, such as information regarding the residual microorganisms persisting in the system and originating from the past rearing conditions. Any studies on microbial communities in RAS mention specific protocols to obtain a similar initial microbial state in their systems before conducting their new studies. In this context, controlling the initial RAS microbial status (before starting a breeding cycle) and having a reliable, standardized protocol for obtaining this state in a reproducible way is essential. In contrast to a standard protocol (i.e. only raw cleaning), this study aimed to evaluate the effects of two treatments that differ in the way of management of biofilter media. The water microbial communities’ structure was assessed through the 16S rRNA gene over two weeks’ post-treatment. The results show that the standard protocol does not shift the microbial past of the tank and is responsible for strong inter-tanks heterogeneity. The testing protocol number T1 is the most reliable for homogenising initial microbial composition of tanks while preserving the microbial communities of interest.