NORDFORSK: RAS-TOOLS: A microbial toolbox for RAS production and innovation.

Increased use of recirculating aquaculture systems (RAS) in fish farming, is a promising strategy for an economically and environmentally sustainable fish industry. Microorganisms constitute an essential component of all RAS facilities, and play a crucial role in maintaining a high water quality and thereby good conditions for the fish. However, there are not only 'good' bacteria in RAS-systems. Some bacteria produce off-flavor compounds, or compounds that are toxic for the fish. Other bacteria are causing diseases. We still know little about the microorganisms in RAS-systems and how they are affected by each other and their surroundings. In the RAS-TOOLS project we will combine mathematical modelling, controlled experiments in small scale RAS-systems, and monitoring of large-scale industrial RAS systems. This will give us a more holistic understanding of how various processes in RAS-systems are connected. Such knowledge will be key for the future development of the RAS-industry. The project is still in its start phase. So far, most of the focus has been on recruitments (1 PhD-student at the University of Bergen, 1 Post-Doc at the University of Copenhagen), establishing a web-page (https://rastools.w.uib.no), and planning of future activities. The kick-off meeting for the project will be arrange in Bergen during 1st-2nd of December 2021.

The use of recirculating aquaculture systems (RAS) in fish farming, is a promising strategy for an economically and environmentally sustainable fish industry. Microorganisms constitute an essential component of all RAS facilities, since they ensure a high water quality by degrading organic matter and oxidizing potentially toxic ammonium to nitrate. A high water quality is vital for maintaining stable RAS conditions that can ensure health and welfare of the fish, as well as profitability of the production. However, microorganisms are not exclusively beneficial to RAS functions. They compete with the fish for oxygen in the water during degradation of organic matter, may produce extremely toxic hydrogen sulfide, and spread diseases. In addition, some of the microorganisms in RAS facilities may also produce off-flavors that accumulate in fish flesh and reduce consumer attraction for aquaculture-produced fish. Yet, little is known about microbiomes in RAS systems, particularly in terms of their mutual dependency and role in RAS system dynamics. The RAS-TOOLS project is driven by innovation, expertise by RAS producers and academic knowledge to develop a novel toolbox for monitoring and control of RAS microbiomes. Through massive sequencing of DNA and RNA to better understand microbial communities and their functions in RAS, we expect to reveal new biosignatures for early detection of non-optimal operational conditions. Through modelling and simulations, we expect to obtain a better holistic understanding of the dynamics of RAS systems, and what effects important operational changes (such as changes in pH, alkalinity, and oxidation procedures) might have for the system as a whole. The RAS-TOOLS project will pave the way for the development of next generation RAS monitoring for better control of water quality and fish health issues, and thereby contribute to the development of a sustainable RAS industry.