63 research outputs found
Novel methanotrophic community assemblages in a terrestrial methane seep in Svalbard
No full textRecent studies have concluded that groundwater driven methane escape through open system pingos is an important greenhouse gas source in the vulnerable high Arctic. In wetlands and marine sediments, large quantities of methane are consumed by methane oxidizing bacteria (MOB) and ANaerobic MEthanotrophic (ANME) archaea, preventing its release to the atmosphere. The methanotrophic capacity of open system pingos is understudied, and microbial community profiling is of key interest, to infer the magnitude of the methane filter and for high resolution prediction of methane evasion. In this thesis, we mapped the microbial community assemblages across hydrological transitions at the open system pingo Lagoon pingo (N78°14’22 E015°45’16). In summer, methane-saturated and oxygen limited groundwater discharges continuously through a main source, forming crater-like ponds, providing potential habitats for methanotrophy. We sampled sediments in August 2019 and coordinated these with methane flux measurements and oxidation rate assays. Environmental parameters and 16S rRNA gene diversity revealed a radial mosaic of habitat patches, made by the seep water. We found distinct and unusual microbial communities inhabiting these habitat patches, suggesting high levels of specialization and adaptation to an unusual terrestrial system with marine influences. Phylogenetic analyses of 16S amplicons unveiled MOB and ANME communities in the crater pond. The MOB sequences were dominated by the type I genus Methylobacter, which was >97% affiliated to the arctic wetland strain Methylobacter tundripaludum SV97. The highest relative abundances of Methylobacter coincided with methane oxidation rates in waterlogged habitats. The distribution of the MOB could not be explained by any environmental parameters measured in this study alone, however it is likely that the MOB are largely controlled by water and/or the dissolved methane, oxygen and nutrients. Surprisingly, Methylobacter was prevalent in sediments continuously flushed with anoxic groundwater, indicating adaptations to oxygen limitation. The archaeal 16S library was dominated by ANME-3 and 2a/b, with lesser representation of ANME-1a. ANME OTU affiliation to sulfate dependent marine clades coincided with sulphur cycling taxa in the source sediments, suggesting a potential for anaerobic oxidation of methane coupled with sulfate reduction, making this an intriguing terrestrial equivalent of cold marine methane seeps. The microbial community we present in this thesis depicts a system contrasting fundamentally from previously reported ecosystems in the Arctic and elsewhere. We confirm that methane is one of the primary energy sources at the seep site and that the atmospheric transfer of methane is mitigated by MOB and possibly ANME
Linking methane fluxes and oxidation rates to methane oxidizing bacteria in an Arctic terrestrial methane seep, Svalbard
No full textGlobal warming has especially detrimental effects on Arctic regions. One major issue is permafrost thaw and sub-permafrost methane escape via surface seeps. While the mitigation potential of methane-consuming bacteria on marine pingo-like methane seeps is well described, terrestrial methane seeps are still understudied. Recently, open system pingos have gained attention as terrestrial methane seeps. Lagoon Pingo (N 78°14'22'', E15°45'16''), a near-shore open system pingo in the Adventdalen valley, Svalbard, was chosen as a study site to investigate the potential impact of methane-oxidizing bacteria on methane evasion from open system pingos. During a fieldwork campaign in August 2019, methane fluxes were measured across the entire site and compared to the distribution of the site’s methane oxidation potentials. The centre of evasion was found at the groundwater-discharging source. The discharged waters were carried away by an associated stream, which gradually emitted methane to a distance of up to 80 meters from the source. While waters from the site were not shown to possess the ability to oxidize methane aerobically, an abundance of methane oxidizing bacteria was found in sediments that were covered with methane emitting waters, creating the potential to oxidize methane. Furthermore, using Lagoon Pingo sediments as inoculum, enrichments have brought a methane oxidizing bacterial strain in culture. This novel Methylobacter sp. seems to produce exospores, a feature not previously described for cultured Methylobacter species. The new knowledge provided by this thesis is a fundament for evaluating the bacterial impact on methane evasion from open system pingos. This in turn could be used to improve predictions of the contribution of open system pingos to the global methane budget
Dynamics and role of microorganisms in the deep-sea sunken wood ecosystem
No full textLorsqu’un morceau de bois atteint le fond de l’océan, il provoque la mise en place d’un écosystème capable de se développer en absence de lumière. Cet écosystème est qualifié de chimiosynthétique du fait de la présence d’une faune pouvant fixer le carbone inorganique présent dans l’eau de mer. De plus, ce système attire une faune ultra-specialisée qui utilise des symbiontes bactériens pour digèrer le bois. Avant ces travaux, la plupart des études s’interressaient principalement à la macrofaune et le rôle des microorganismes libres demeurait inconnu. Nous avons pu démontrer dans cette thèse le rôle essentiel que jouent les microorganismes libres dans la mise en place de cet écosystème. Nous avons prouvé que des communautés de microorganismes se succédaient au cours de la première année de colonisation et que cette succession était influencée par le type de bois et l’environment dans lequel il se trouve. La première phase de cette succession aboutit au développement après un mois, d’une population de bactéries sulfato-réductrices produisant de l’hydrogène sulfuré et ce, même en l’absence d’organismes foreurs. Cette production d’hydrogène sulfuré est à la base (1) du développement rapide d’un biofilm chimiolithoautotrophe et (2) du recrutement d’espèces possédants des symbiontes chimiosynthétiques. Nos résultats ont permis d’aboutir à la proposition d’une succession d’étapes clés liées permettant la transformation d’un substrat térrigène en un écosysteme qui, il y a plusieurs millions d’années, aurait permis à la faune chimiosynthétique de coloniser les grands fonds.When wood sinks to the deep-sea floor it creates a new ecosystem that does not depend directly on energy from sunlight. This ecosystem is called chemosynthetic because of the presence of a fauna associated with symbiotic bacteria that can assimilate inorganic carbon from seawater. Furthermore this system is colonized by specialized fauna that use symbiotic bacteria to digest the wood matrix. Previous studies mostly focused on these symbiotic macroorganisms and the role played by non-symbiotic microorganisms in the sunken wood ecosystem remains unknown. We demonstrate in this thesis the important role played by non symbiotic microorganisms during the sunken wood ecosystem establishment. We reveal the ecological succession of microorganisms driven by time and wood structure. The first step of this succession is characterized by a microbial population able to produce hydrogen sulfide after one month of immersion. This hydrogen sulfide production is the basis for (1) a chemolithoautotroph biofilm development on the wood surface and (2) a recruitment of species associated with chemoautotrophic bacteria. Our results suggest a succession of different phases that transform a terrigeneous substrate into an environment that may have helped, million years ago, the colonization of the deep sea by chemosynthetic species
Dynamique et rôle des microorganismes dans l'écosystème bois coulé en milieu profond
No full textWhen wood sinks to the deep-sea floor it creates a new ecosystem that does not depend directly on energy from sunlight. This ecosystem is called chemosynthetic because of the presence of a fauna associated with symbiotic bacteria that can assimilate inorganic carbon from seawater. Furthermore this system is colonized by specialized fauna that use symbiotic bacteria to digest the wood matrix. Previous studies mostly focused on these symbiotic macroorganisms and the role played by non-symbiotic microorganisms in the sunken wood ecosystem remains unknown. We demonstrate in this thesis the important role played by non symbiotic microorganisms during the sunken wood ecosystem establishment. We reveal the ecological succession of microorganisms driven by time and wood structure. The first step of this succession is characterized by a microbial population able to produce hydrogen sulfide after one month of immersion. This hydrogen sulfide production is the basis for (1) a chemolithoautotroph biofilm development on the wood surface and (2) a recruitment of species associated with chemoautotrophic bacteria. Our results suggest a succession of different phases that transform a terrigeneous substrate into an environment that may have helped, million years ago, the colonization of the deep sea by chemosynthetic species.Lorsqu’un morceau de bois atteint le fond de l’océan, il provoque la mise en place d’un écosystème capable de se développer en absence de lumière. Cet écosystème est qualifié de chimiosynthétique du fait de la présence d’une faune pouvant fixer le carbone inorganique présent dans l’eau de mer. De plus, ce système attire une faune ultra-specialisée qui utilise des symbiontes bactériens pour digèrer le bois. Avant ces travaux, la plupart des études s’interressaient principalement à la macrofaune et le rôle des microorganismes libres demeurait inconnu. Nous avons pu démontrer dans cette thèse le rôle essentiel que jouent les microorganismes libres dans la mise en place de cet écosystème. Nous avons prouvé que des communautés de microorganismes se succédaient au cours de la première année de colonisation et que cette succession était influencée par le type de bois et l’environment dans lequel il se trouve. La première phase de cette succession aboutit au développement après un mois, d’une population de bactéries sulfato-réductrices produisant de l’hydrogène sulfuré et ce, même en l’absence d’organismes foreurs. Cette production d’hydrogène sulfuré est à la base (1) du développement rapide d’un biofilm chimiolithoautotrophe et (2) du recrutement d’espèces possédants des symbiontes chimiosynthétiques. Nos résultats ont permis d’aboutir à la proposition d’une succession d’étapes clés liées permettant la transformation d’un substrat térrigène en un écosysteme qui, il y a plusieurs millions d’années, aurait permis à la faune chimiosynthétique de coloniser les grands fonds
Phylogenetic_distance_matrix
No full textThe file contains the phylogenetic distance matrix calculated with the comdistnt function in the Picante R package
Ecosystem productivity is associated with bacterial phylogenetic distance in surface marine waters
No full textUnderstanding the link between community diversity and ecosystem function is a fundamental aspect of ecology. Systematic losses in biodiversity are widely acknowledged but the impact this may exert on ecosystem functioning remains ambiguous. There is growing evidence of a positive relationship between species richness and ecosystem productivity for terrestrial macro-organisms, but similar links for marine micro-organisms, which help drive global climate, are unclear. Community manipulation experiments show both positive and negative relationships for microbes. These previous studies rely, however, on artificial communities and any links between the full diversity of active bacterial communities in the environment, their phylogenetic relatedness and ecosystem function remain hitherto unexplored. Here, we test the hypothesis that productivity is associated with diversity in the metabolically active fraction of microbial communities. We show in natural assemblages of active bacteria that communities containing more distantly related members were associated with higher bacterial production. The positive phylogenetic diversity–productivity relationship was independent of community diversity calculated as the Shannon index. From our long-term (7-year) survey of surface marine bacterial communities, we also found that similarly, productive communities had greater phylogenetic similarity to each other, further suggesting that the traits of active bacteria are an important predictor of ecosystem productivity. Our findings demonstrate that the evolutionary history of the active fraction of a microbial community is critical for understanding their role in ecosystem functioning
Video images from ROV ÆGIR6000 in Kongsfjorden during the CAGE 20-7 cruise
No full textThe dataset includes two videos taken during an ROV ÆGIR6000 dive in Kongsfjorden on November 12th 2020 (11.628E; 78.98N; 308m depth). The cruise name was CAGE 20-7 and the cruise leader Benedicte Ferré. This cruise was funded by CAGE (Centre for Arctic Gas Hydrate, Environment and Climate), Norwegian Research Council grant no. 22325
Historical contingency impacts on community assembly and ecosystem function in chemosynthetic marine ecosystems
No full textAbstract Predicting ecosystem functioning requires an understanding of the mechanisms that drive microbial community assembly. Many studies have explored microbial diversity extensively and environmental factors are thought to be the principal drivers of community composition. Community assembly is, however, also influenced by past conditions that might affect present-day assemblages. Historical events, called legacy effects or historical contingencies, remain poorly studied in the sea and their impact on the functioning of the communities is not known. We tested the influence, if any, of historical contingencies on contemporary community assembly and functions in a marine ecosystem. To do so, we verified if different inoculum communities colonizing the same substrate led to communities with different compositions. We inoculated wood with sea water microbes from different marine environments that differ in ecological and evolutionary history. Using 16S rRNA and metagenomic sequencing, it was demonstrated that historical contingencies change the composition and potential metabolisms of contemporary communities. The effect of historical events was transient, dominated by environmental selection as, over time, species sorting was a more important driver of community assembly. Our study shows not only that historical contingencies affect marine ecosystems but takes the analysis a step further by characterizing this effect as strong but transient
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