Microbial Ecology of Atlantic Salmon (Salmo salar) Hatcheries: Impacts of the Built Environment on Fish Mucosal Microbiota.
ABSTRACT: Successful rearing of fish in hatcheries is critical for conservation, recreational fishing, commercial fishing through wild stock enhancements, and aquaculture production. Flowthrough (FT) hatcheries require more water than recirculating aquaculture systems (RAS), which enable up to 99% of their water to be recycled, thus significantly reducing environmental impacts. Here, we evaluated the biological and physical microbiome interactions of three Atlantic salmon hatcheries (RAS n?=?2, FT n?=?1). Gill, skin, and digesta from six juvenile fish along with tank biofilms and water were sampled from tanks in each of the hatcheries (60 fish across 10 tanks) to assess the built environment and mucosal microbiota using 16S rRNA gene sequencing. The water and tank biofilm had more microbial richness than fish mucus, while skin and digesta from RAS fish had 2 times the richness of FT fish. Body sites each had unique microbiomes (P?P?IMPORTANCE Atlantic salmon, Salmo salar, is the most farmed marine fish worldwide, with an annual production of 2,248 million metric tons in 2016. Salmon hatcheries are increasingly changing from flowthrough toward recirculating aquaculture system (RAS) design to accommodate more control over production along with improved environmental sustainability due to lower impacts on water consumption. To date, microbiome studies of hatcheries have focused either on the fish mucosal microbiota or on the built environment microbiota but have not combined the two to understand their interactions. Our study evaluates how the water and tank biofilm microbiota influences the fish microbiota across three mucosal environments (gill, skin, and digesta). Results from this study highlight how the built environment is a unique source of microbes to colonize fish mucus and, furthermore, how this can influence fish health. Further studies can use this knowledge to engineer built environments to modulate fish microbiota for beneficial phenotypes.
Project description:A marine aquaculture recycling system (RAS) for the production of post-smolt was monitored for microbial community structures during the first year of operation. Sample material was obtained monthly from the biofilter biofilm carriers, the production water (tank 3), the fish skin (tank 3) and the tank 3 wall biofilm. Additional samples were taken during outbreaks of fish skin wounds, washing of the plant, UV filtration of the inlet water and from various wall biofilms. Samples for depth profiles from all fish tanks were also collected. The sampling tools were a ladle for capturing biofilter biofilm carriers, toothbrushes for wall biofilm capture, filters for capture of water microbes and scalpels for skin tissue slicing. The sampling times were indicated by the production cycle number (cycle 2-5) and the week number within the cycle (W). Prior to bacterial community analysis, the stored samples were exposed to cell lysis and extraction of environmental DNA by commercial kits. All samples were subjected for PCR amplification of 16S rDNA sequences for library formations and prepared for Ion Torrent technology, which sequences 250 bp fragments. A total of 1.1 million reads were obtained from the 100 RAS samples analysed. The process from Ion Torren analysis to library involved bioinformatics steps with sorting, filtering, adjustment and taxonomic identification, and the final output was shown in a table as operational taxonomic units (OTUs) and relative abundance at different sampling sites and sampling time points. Of a total of 450 taxonomically assigned OTUs, 45% were classified at genus level. The 16S library raw data are deposited in the Mendeley data repository and cited in this Data in Brief article co-submitted with the article "Microbial colonization and stability in a marine post-smolt RAS inoculated with a commercial starter culture." . So far, the raw data are referenced in four more publications in progress. These cover microbial shifts and enrichments between sampling times, sulfur cycling, "in vivo biofilm" and identification of relatives of fish pathogens in RAS. All library sequences are available in GenBank with accession numbers MN890148-MN891672.
Project description:<h4>Background</h4>The eco-evolutionary processes ruling post-disturbance microbial assembly remain poorly studied, particularly in host-microbiome systems. The community recovery depends not only on the type, duration, intensity, and gradient of disturbance, but also on the initial community structure, phylogenetic composition, legacy, and habitat (soil, water, host). In this study, yellow perch (Perca flavescens) juveniles were exposed over 90 days to constant and gradual sublethal doses of cadmium chloride. Afterward, the exposure of aquaria tank system to cadmium was ceased for 60 days. The skin, gut and water tank microbiomes in control and treatment groups, were characterized before, during and after the cadmium exposure using 16s rDNA libraries and high throughput sequencing technology (Illumina, Miseq).<h4>Results</h4>Our data exhibited long-term bioaccumulation of cadmium salts in the liver even after two months since ceasing the exposure. The gradient of cadmium disturbance had differential effects on the perch microbiota recovery, including increases in evenness, taxonomic composition shifts, as well as functional and phylogenetic divergence. The perch microbiome reached an alternative stable state in the skin and nearly complete recovery trajectories in the gut communities. The recovery of skin communities showed a significant proliferation of opportunistic fish pathogens (i.e., Flavobacterium). Our findings provide evidence that neutral processes were a much more significant contributor to microbial community turnover in control treatments than in those treated with cadmium, suggesting the role of selective processes in driving community recovery.<h4>Conclusions</h4>The short-term metallic disturbance of fish development has important long-term implications for host health. The recovery of microbial communities after metallic exposure depends on the magnitude of exposure (constant, gradual), and the nature of the ecological niche (water, skin, and gut). The skin and gut microbiota of fish exposed to constant concentrations of cadmium (CC) were closer to the control negative than those exposed to the gradual concentrations (CV). Overall, our results show that the microbial assembly during the community recovery were both orchestrated by neutral and deterministic processes. Video Abtract.
Project description:Fish skin and gut microbiomes contribute to host health and growth and are often significantly different in aquaculture-reared fish compared to wild fish. Determining how factors associated with aquaculture, including altered diet and abiotic conditions, affect the microbiome will assist with optimizing farming practices and non-invasively assessing fish health. Here, juvenile yellowtail kingfish (Seriola lalandi) housed at optimal (22 °C) and non-optimal (26 °C) water temperature were fed a fishmeal control diet or the same diet substituted with 30% soy-protein concentrate (SPC) in order to investigate impacts on host health and the microbial community composition of the skin mucosa, gut mucosa and digesta. Each of these sites was observed to have a distinct microbiome composition. The combination of SPC and housing at 26 °C significantly reduced weight gain in yellowtail kingfish and affected immune parameters. The overall microbial composition and relative abundance of specific operational taxonomic units (OTUs) was also significantly altered by inclusion of SPC at 26 °C, with a notable increase in an OTU identified as Photobacterium in the skin mucosa and digesta. Increased relative abundance of Photobacterium sp. was significantly correlated with reduced levels of digesta myeloperoxidase in yellowtail kingfish; a recognized innate immunity defense mechanism. The changes in the microbial communities of yellowtail kingfish fed a diet containing 30% SPC at 26 °C highlights the importance of considering the interactive effects of diet and environmental factors on microbiome health in farmed yellowtail kingfish.
Project description:Ballan wrasse (Labrus bergylta, Ascanius 1767) are cleaner fish cultured in northern Europe to remove sea lice from farmed Atlantic salmon (Salmo salar, Linnaeus 1758). Despite increasing appreciation for the importance of the microbiota on the phenotypes of vertebrates including teleosts, the microbiota of wrasse eggs has yet to be described. Therefore, the aim of this present study was to describe the bacterial component of the microbiota of ballan wrasse eggs shortly after spawning and at 5 days, once the eggs had undergone a routine incubation protocol that included surface disinfection steps in a common holding tank. Triplicate egg samples were collected from each of three spawning tanks and analysis of 16S rRNA gene sequences revealed that 88.6% of reads could be identified to 186 taxonomic families. At Day 0, reads corresponding to members of the Vibrionaceae, Colwelliaceae and Rubritaleaceae families were detected at greatest relative abundances. Bacterial communities of eggs varied more greatly between tanks than between samples deriving from the same tank. At Day 5, there was a consistent reduction in 16S rRNA gene sequence richness across the tanks. Even though the eggs from the different tanks were incubated in a common holding tank, the bacterial communities of the eggs from the different tanks had diverged to become increasingly dissimilar. This suggests that the disinfection and incubation exerted differential effects of the microbiota of the eggs from each tank and that the influence of the tank water on the composition of the egg microbiota was lower than expected. This first comprehensive description of the ballan wrasse egg bacterial community is an initial step to understand the role and function of the microbiota on the phenotype of this fish. In future, mass DNA sequencing methods may be applied in hatcheries to screen for pathogens and as a tool to assess the health status of eggs.
Project description:Flowthrough and pond aquaculture system microbiome management practices aim to mitigate fish disease and stress. However, the operational success of recirculating aquaculture systems (RAS) depends directly on system microbial community activities. In RAS, each component environment is engineered for a specific microbial niche for waste management, as the water continuously flowing through the system must be processed before returning to the rearing tank. In this study, we compared waste management component microbiomes (rearing tank water, pH correction tank, solid-waste clarifier, biofilter, and degassing tower) within a commercial-scale freshwater RAS by high-throughput 16S rRNA gene sequencing. To assess consistency among freshwater RAS microbiomes, we also compared the microbial community compositions of six aquaculture and aquaponic farms. Community assemblages reflected site and source water relationships, and the presence of a hydroponic subsystem was a major community determinant. In contrast to the facility-specific community composition, some sequence variants, mainly classified into Flavobacterium, Cetobacterium, the family Sphingomonadaceae, and nitrifying guilds of ammonia-oxidizing archaea and Nitrospira, were common across all facilities. The findings of this study suggest that, independently of system design, core taxa exist across RAS rearing similar fish species but that system design informs the individual aquatic microbiome assemblages. Future RAS design would benefit from understanding the roles of these core taxa and then capitalizing on their activities to further reduce system waste/added operational controls.IMPORTANCE Recirculating aquaculture systems (RAS) are agroecosystems for intensive on-land cultivation of products of fisheries. Practitioners that incorporate edible plant production into RAS refer to these facilities as aquaponic systems (AP). RAS have the potential to offset declining production levels of wild global fisheries while reducing waste and product distance to market, but system optimization is needed to reduce costs. Both RAS and AP rely on microbial consortia for maintaining water quality and promoting fish/plant health, but little is known about the microorganisms actually present. This lack of knowledge prevents optimization of designs and operational controls to target the growth of beneficial microbial species or consortia. The significance of our research is in identifying the common microorganisms that inhabit production RAS and AP and the operational factors that influence which microorganisms colonize and become abundant. Identifying these organisms is a first step toward advanced control of microbial activities that improve reproducibility and reduce costs.
Project description:The gut microbiota of fish larvae evolves fast towards a complex community. Both host and environment affect the development of the gut microbiota; however, the relative importance of both is poorly understood. Determining specific changes in gut microbial populations in response to a change in an environmental factor is very complicated. Interactions between factors are difficult to separate and any response could be masked due to high inter-individual variation even for individuals that share a common environment. In this study we characterized and quantified the spatio-temporal variation in the gut microbiota of tilapia larvae, reared in recirculating aquaculture systems (RAS) or active suspension tanks (AS). Our results showed that variation in gut microbiota between replicate tanks was not significantly higher than within tank variation, suggesting that there is no tank effect on water and gut microbiota. However, when individuals were reared in replicate RAS, gut microbiota differed significantly. The highest variation was observed between individuals reared in different types of system (RAS vs. AS). Our data suggest that under experimental conditions in which the roles of deterministic and stochastic factors have not been precisely determined, compositional replication of the microbial communities of an ecosystem is not predictable.
Project description:The microbiome has a crucial influence on host phenotype and is of broad interest to ecological and evolutionary research. Yet, the extent of variation that occurs in the microbiome within and between populations is unclear. We characterized the skin and gut microbiomes of seven populations of juvenile Atlantic salmon (Salmo salar) inhabiting a diverse range of environments, including hatchery-reared and wild populations. We found shared skin operational taxonomic units (OTUs) across all populations and core gut microbiota for all wild fish, but the diversity and structure of both skin and gut microbial communities were distinct between populations. There was a marked difference between the gut microbiomes of wild and captive fish. Hatchery-reared fish had lower intestinal microbial diversity, lacked core microbiota found in wild fish, and showed altered community structure and function. Skin and gut microbiomes were also less varied within captive populations, reflecting more uniform artificial rearing conditions. The surrounding water influenced the microbiome of the gut and, especially, the skin, but could not explain the degree of variation observed between populations. For both gut and skin, we found that there was greater difference in microbiome structures between more genetically distinct fish populations, and that population genetic diversity was positively correlated with microbiome diversity. However, diet is likely to be the major factor contributing to the large differences in gut microbiota between wild and captive fish. Our results highlight the scope of interpopulation variation in the Atlantic salmon microbiome and offer insights into the deterministic factors contributing to microbiome diversity and structure.IMPORTANCE Variation in the microbiome has a fundamental influence on host health, ecology, and evolution, but the scope and basis of this variation are not fully understood. We identified considerable variation in skin and gut microbial communities between seven wild and captive populations of Atlantic salmon, reflecting divergent environmental conditions and fish genetic diversity. In particular, we found very pronounced differences in the intestinal microbiomes of wild and hatchery-reared fish, likely reflecting differences in diet. Our results offer an insight into how the microbiome potentially contributes to the generation of local adaptations in this species and how domestication alters intestinal microbial communities, highlighting future research directions in these areas.
Project description:Aquaculture is the fastest growing primary industry worldwide. Marine finfish culture in open ocean net pens, or pontoons, is one of the largest growth areas and is currently the only way to rear high value fish such as bluefin tuna. Ranching involves catching wild juveniles, stocking in floating net pens and fattening for 4 to 8 months. Tuna experience several parasite-induced disease challenges in culture that can be mitigated by application of praziquantel (PZQ) as a therapeutic. In this study, we characterized the microbiome of ranched southern Bluefin Tuna, Thunnus maccoyii, across four anatomic sites (gill, skin, digesta, and anterior kidney) and evaluated environmental and pathological factors that influence microbiome composition, including the impact of PZQ treatment on microbiome stability. Southern bluefin tuna gill, skin, and digesta microbiome communities are unique and potentially influenced by husbandry practices, location of pontoon growout pens, and treatment with the antiparasitic PZQ. There was no significant relationship between the fish mucosal microbiome and incidence or abundance of adult blood fluke in the heart or fluke egg density in the gill. An enhanced understanding of microbiome diversity and function in high-value farmed fish species such as bluefin tuna is needed to optimize fish health and improve aquaculture yield. Comparison of the bluefin tuna microbiome to other fish species, including Seriola lalandi (yellowtail kingfish), a common farmed species from Australia, and Scomber japonicus (Pacific mackerel), a wild caught Scombrid relative of tuna, showed the two Scombrids had more similar microbial communities compared to other families. The finding that mucosal microbial communities are more similar in phylogenetically related fish species exposes an opportunity to develop mackerel as a model for tuna microbiome and parasite research.
Project description:<h4>Background</h4>Zebrafish used in research settings are often housed in recirculating aquaculture systems (RAS) which rely on the system microbiome, typically enriched in a biofiltration substrate, to remove the harmful ammonia generated by fish via oxidation. Commercial RAS must be allowed to equilibrate following installation, before fish can be introduced. There is little information available regarding the bacterial community structure in commercial zebrafish housing systems, or the time-point at which the system or biofilter reaches a microbiological equilibrium in RAS in general.<h4>Methods</h4>A zebrafish housing system was monitored at multiple different system sites including tank water in six different tanks, pre- and post-particulate filter water, the fluidized bed biofilter substrate, post-carbon filter water, and water leaving the ultra-violet (UV) disinfection unit and entering the tanks. All of these samples were collected in quadruplicate, from prior to population of the system with zebrafish through 18 weeks post-population, and analyzed using both 16S rRNA amplicon sequencing and culture using multiple agars and annotation of isolates via matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry. Sequencing data were analyzed using traditional methods, network analyses of longitudinal data, and integration of culture and sequence data.<h4>Results</h4>The water microbiome, dominated by Cutibacterium and Staphylococcus spp., reached a relatively stable richness and composition by approximately three to four weeks post-population, but continued to evolve in composition throughout the study duration. The microbiomes of the fluidized bed biofilter and water leaving the UV disinfection unit were distinct from water at all other sites. Core taxa detected using molecular methods comprised 36 amplicon sequence variants, 15 of which represented Proteobacteria including multiple members of the families Burkholderiaceae and Sphingomonadaceae. Culture-based screening yielded 36 distinct isolates, and showed moderate agreement with sequencing data.<h4>Conclusions</h4>The microbiome of commercial RAS used for research zebrafish reaches a relatively stable state by four weeks post-population and would be expected to be suitable for experimental use following that time-point.
Project description:<h4>Background</h4>The skin microbiome of marine fish is thought to come from bacteria in the surrounding water during the larval stages, although it is not clear how different water conditions affect the microbial communities in the water and, in turn, the composition and development of the larval skin microbiome. In aquaculture, water conditions are especially important; claywater and greenwater are often used in larval rearing tanks to increase water turbidity. Here, we explored the effects of these water additives on microbial communities in rearing water and on the skin of first-feeding sablefish larvae using 16S rRNA gene sequencing. We evaluated three treatments: greenwater, claywater, and greenwater with a switch to claywater after 1 week.<h4>Results</h4>We observed additive-specific effects on rearing water microbial communities that coincided with the addition of larvae and rotifer feed to the tanks, such as an increase in Vibrionaceae in greenwater tanks. Additionally, microbial communities from experimental tank water, especially those in claywater, began to resemble larval skin microbiomes by the end of the experiment. The differential effects of the additives on larval sablefish skin microbiomes were largest during the first week, post-first feed. Bacteria associated with greenwater, including Vibrionaceae and Pseudoalteromonas spp., were found on larval skin a week after the switch to claywater. In addition to additive-specific effects, larval skin microbiomes also retained bacterial families likely acquired from their hatchery silos.<h4>Conclusions</h4>Our results suggest that larval sablefish skin microbiomes are most sensitive to the surrounding seawater up to 1 week following the yolk-sac stage and that claywater substituted for greenwater after 1 week post-first feed does not significantly impact skin-associated microbial communities. However, the larval skin microbiome changes over time under all experimental conditions. Furthermore, our findings suggest a potential two-way interaction between microbial communities on the host and the surrounding environment. To our knowledge, this is one of the few studies to suggest that fish might influence the microbial community of the seawater.