Periodic Reporting for period 1 - RASOPTA (Safeguarding future production of fish in aquaculture systems with water recirculation)
Berichtszeitraum: 2021-09-01 bis 2023-08-31
Production of food for humans is in great demand. Fish represent a significant protein source for human consumption and aquaculture industries have increased their productions globally. But issues with environmental impact persist and there is a need for development of environmentally friendly production systems. Recirculated Aquaculture Systems (RAS) represent such systems, where up to 100% of the water is recirculated and the outlet of nutrients is controlled. In RAS there are different challenges impairing production that are addressed in this project, and the project aims to train 12 early stage researchers (ESRs) in novel approaches to understand, characterize and control 1) water quality, 2) off-flavours and 3) fish health and welfare.
RASOPTA has recruited and trains 12 doctoral students. In work package 1 (WP1), focused on water quality, 3 ESRs are involved. In WP2, focused on off-flavor, 4 ESRs are involved and in WP3, focused on fish health and welfare, 5 ESRs are involved.
In WP1 biofilter microbiomes, fish microbiomes and water microbiomes are scrutinized. Biofilters are mandatory in RAS to convert the toxic ammonia to less harmful nitrate, but it is not well described how the biofilter communities impact the communities in the water. In this project it has been found that cleaning of moving bed biofilters enhance the risk of favoring heterotrophic microorganisms, not desirable in RAS systems, and that biofilter communities impact the water microbiome and the fish skin microbiome. The WP looks at suspended solids derived from fecal matter and feed waste which challenge RAS with high water reuse. A new technology mixing cork in fish feed to make the fecal matter float has been implemented with success. More fecal removal was obtained using cork and no impact was detected on growth rates, feed conversion efficiency and nutrient digestibility of the fish. To reduce the amount of fish fecal particles, replacing soybean with black soldier fly larvae was investigated. No differences in performance were detected but the fish had to eat a higher amount of the new feed to obtain the same performance. Another aim is to quantify the external contribution of bacteria (intake water, microalgae, live feeds) and internal growth of bacteria in three types rearing systems. A major finding was that internal bacterial growth was significantly lower in RAS fish tanks. Results showed that the biofilter stabilized the microbiota in the rearing environment.
In WP2 the focus is to better understand and manage off-flavour generation and removal in RAS. This includes documentation on the origin of off-flavor, descriptions of the smells, off-flavor chemical compounds and off-flavor inducing compounds in fish feed, and degradation of off-flavor compounds. The microbiological production and degradation of geosmin was investigated. Three different myxobacteria were isolated and studied for their geosmin production - two were found to produce geosmin on a high level. A plasmid was constructed to investigate regulations of geosmin on gene level. With this tool it can be investigated which compounds stimulate production of geosmin. Optimization is ongoing to quantify low concentrations of these compounds. A chromatography-based setup is tested to study odor mixtures, for a better understanding of the relevance of geosmin, 2-methylisoborneol and other fish off-flavors in RAS. Odor-active compounds and aroma profiles have also been investigated in Nile Tilapia, Sturgeon, Sturgeon RAS water and caviar from commercial RAS farms. Several odorants were for the first time identified in RAS fish. Results showed that feeding vs not feeding increased the diversity of off-odour compounds in fish flesh - but reduced the dominance of potent waterborne and feed-borne off odours. Rhodomonas salina microalgal biomass is tested as ingredient in aquaculture feed for Atlantic salmon in relation to off-flavor issues.
In WP3 focus is on fish health and welfare and a Fluidigm chip is developed to detect pathogens, water quality and off-flavours only using water samples. In RAS, diseases are a major issue, and it is known that stressed fish are more prone to infection. A task in this WP is to identify health and welfare indicators to pinpoint stress and immune-compromising parameters. A result is that plastic particles were found in the tissues of fish after exposure to nanoplastics. It was found that transport, hypoxia, overcrowding, nanoplastics and pharceuticals influence the stress level, which can rapidly be assessed by using a non-lethal analysis of blood (powerful tool). To avoid introduction of diseases, biosecurity control is of vital importance, and analyses of pathogens in water and air were investigated. The pathogens were found in the water, but a significant result was that pathogens were also detected in aerosols in RAS facilities and therefore transmission of diseases through air may represent a potential danger. A recommendation of pathogens plus RNA samples of IPNV, ISAV, SGPV, PRV-1, and PMCV have been provided to ESR 12 to be incorporated into the Fluidigm chip. To make this chip it is necessary to know how levels of pathogen environmental DNA/RNA (eDNA/eRNA) in the water relates to the disease status of the fish. It was found that the amount of eDNA/eRNA in water correlates well with the disease status and mortality in the fish of 3 diseases. An estimation of a threshold level of eDNA/eRNA in the water indicating when the disease becomes serious was described, to describe presence and diversity of external pathogenic and commensal parasites in RAS. The presence of ectoparasites was determined. It was found that heavy infections were associated with high mortality among host fish. Purified DNA collected (reference DNA) was sent to ESR12 and here a qPCR assay was developed. An aim is to develop a novel high-throughput technological tool (Fluidigm chip) to detect pathogens, off-flavor production and water quality. The assays were divided into two chips – one with eDNA and one with eRNA as template. 41 pathogenic organisms, comprising 17 viruses, 11 bacteria, 10 parasites and 3 fungi, were selected for fish health monitoring. The design of the chip is completed and most assays have been validated. Next step is to test the chip with water samples.
In WP1 biofilter microbiomes, fish microbiomes and water microbiomes are scrutinized. Biofilters are mandatory in RAS to convert the toxic ammonia to less harmful nitrate, but it is not well described how the biofilter communities impact the communities in the water. In this project it has been found that cleaning of moving bed biofilters enhance the risk of favoring heterotrophic microorganisms, not desirable in RAS systems, and that biofilter communities impact the water microbiome and the fish skin microbiome. The WP looks at suspended solids derived from fecal matter and feed waste which challenge RAS with high water reuse. A new technology mixing cork in fish feed to make the fecal matter float has been implemented with success. More fecal removal was obtained using cork and no impact was detected on growth rates, feed conversion efficiency and nutrient digestibility of the fish. To reduce the amount of fish fecal particles, replacing soybean with black soldier fly larvae was investigated. No differences in performance were detected but the fish had to eat a higher amount of the new feed to obtain the same performance. Another aim is to quantify the external contribution of bacteria (intake water, microalgae, live feeds) and internal growth of bacteria in three types rearing systems. A major finding was that internal bacterial growth was significantly lower in RAS fish tanks. Results showed that the biofilter stabilized the microbiota in the rearing environment.
In WP2 the focus is to better understand and manage off-flavour generation and removal in RAS. This includes documentation on the origin of off-flavor, descriptions of the smells, off-flavor chemical compounds and off-flavor inducing compounds in fish feed, and degradation of off-flavor compounds. The microbiological production and degradation of geosmin was investigated. Three different myxobacteria were isolated and studied for their geosmin production - two were found to produce geosmin on a high level. A plasmid was constructed to investigate regulations of geosmin on gene level. With this tool it can be investigated which compounds stimulate production of geosmin. Optimization is ongoing to quantify low concentrations of these compounds. A chromatography-based setup is tested to study odor mixtures, for a better understanding of the relevance of geosmin, 2-methylisoborneol and other fish off-flavors in RAS. Odor-active compounds and aroma profiles have also been investigated in Nile Tilapia, Sturgeon, Sturgeon RAS water and caviar from commercial RAS farms. Several odorants were for the first time identified in RAS fish. Results showed that feeding vs not feeding increased the diversity of off-odour compounds in fish flesh - but reduced the dominance of potent waterborne and feed-borne off odours. Rhodomonas salina microalgal biomass is tested as ingredient in aquaculture feed for Atlantic salmon in relation to off-flavor issues.
In WP3 focus is on fish health and welfare and a Fluidigm chip is developed to detect pathogens, water quality and off-flavours only using water samples. In RAS, diseases are a major issue, and it is known that stressed fish are more prone to infection. A task in this WP is to identify health and welfare indicators to pinpoint stress and immune-compromising parameters. A result is that plastic particles were found in the tissues of fish after exposure to nanoplastics. It was found that transport, hypoxia, overcrowding, nanoplastics and pharceuticals influence the stress level, which can rapidly be assessed by using a non-lethal analysis of blood (powerful tool). To avoid introduction of diseases, biosecurity control is of vital importance, and analyses of pathogens in water and air were investigated. The pathogens were found in the water, but a significant result was that pathogens were also detected in aerosols in RAS facilities and therefore transmission of diseases through air may represent a potential danger. A recommendation of pathogens plus RNA samples of IPNV, ISAV, SGPV, PRV-1, and PMCV have been provided to ESR 12 to be incorporated into the Fluidigm chip. To make this chip it is necessary to know how levels of pathogen environmental DNA/RNA (eDNA/eRNA) in the water relates to the disease status of the fish. It was found that the amount of eDNA/eRNA in water correlates well with the disease status and mortality in the fish of 3 diseases. An estimation of a threshold level of eDNA/eRNA in the water indicating when the disease becomes serious was described, to describe presence and diversity of external pathogenic and commensal parasites in RAS. The presence of ectoparasites was determined. It was found that heavy infections were associated with high mortality among host fish. Purified DNA collected (reference DNA) was sent to ESR12 and here a qPCR assay was developed. An aim is to develop a novel high-throughput technological tool (Fluidigm chip) to detect pathogens, off-flavor production and water quality. The assays were divided into two chips – one with eDNA and one with eRNA as template. 41 pathogenic organisms, comprising 17 viruses, 11 bacteria, 10 parasites and 3 fungi, were selected for fish health monitoring. The design of the chip is completed and most assays have been validated. Next step is to test the chip with water samples.
Developing a non-invasive tool to surveille water instead of fish in recirculated aquaculture systems focusing on water quality, off-flavour and pathogens move control methods and management strategies in fish farming beyond state-of-the-art. With this tool farmers will be able to regularly non-invasively surveille their farms and conduct preventive measures when problems arise and is revealed on the chip. With a lot of data collections using the chip, we will even be able to foresee problems and prevent them. This will result in an increase in production of fish for human consumption, increased health and welfare of the fish, reduced environmental impact, improved sustainability and economy and increase the socio-economic value.
There is a lack of knowledge on what causes production of off-flavour and a tool beyond state-of-the-art has been developed to discover inducers of geosmin (off-flavour) production.
Using cork in the feed is also beyond state-of-the-art. This new technology that increases particle removement in the RAS farms may have a positive impact on water quality and fish health and production.
There is a lack of knowledge on what causes production of off-flavour and a tool beyond state-of-the-art has been developed to discover inducers of geosmin (off-flavour) production.
Using cork in the feed is also beyond state-of-the-art. This new technology that increases particle removement in the RAS farms may have a positive impact on water quality and fish health and production.