Articles de revues : « Océan archéen »

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Rüpke, Lars, et Fabrice Gaillard. « The Geological History of Water : From Earth’s Accretion to the Modern Deep Water Cycle ». Elements 20, n^o 4 (1 août 2024) : 253–58. http://dx.doi.org/10.2138/gselements.20.4.253.

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The abundance of water on Earth and its distribution between surficial and deep reservoirs are the outcome of 4.6 billion years of geological history involving various mechanisms of water in and outgassing. Here, we use the metaphor of a pipeline connecting Earth’s deep and surface water reservoirs. The net flux through this pipeline has changed over time due to contrasting Hadean, Archean, and modern geodynamic regimes. Most water was dissolved in the primordial magma ocean, entrapped in the solidifying mantle, and massively released by volcanism during the Hadean and Archaean. As Earth cooled, plate tectonics enabled water ingassing into the mantle, which appears to exceed outgassing under the modern tectonic regime, implying that Earth’s surface has been drying out and will continue to do so.

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Bano, Nasreen, Shomari Ruffin, Briana Ransom et James T. Hollibaugh. « Phylogenetic Composition of Arctic Ocean Archaeal Assemblages and Comparison with Antarctic Assemblages ». Applied and Environmental Microbiology 70, n^o 2 (février 2004) : 781–89. http://dx.doi.org/10.1128/aem.70.2.781-789.2004.

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ABSTRACT Archaea assemblages from the Arctic Ocean and Antarctic waters were compared by PCR-denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA genes amplified using the Archaea-specific primers 344f and 517r. Inspection of the DGGE fingerprints of 33 samples from the Arctic Ocean (from SCICEX submarine cruises in 1995, 1996, and 1997) and 7 Antarctic samples from Gerlache Strait and Dallman Bay revealed that the richness of Archaea assemblages was greater in samples from deep water than in those from the upper water column in both polar oceans. DGGE banding patterns suggested that most of the Archaea ribotypes were common to both the Arctic Ocean and the Antarctic Ocean. However, some of the Euryarchaeota ribotypes were unique to each system. Cluster analysis of DGGE fingerprints revealed no seasonal variation but supported depth-related differences in the composition of the Arctic Ocean Archaea assemblage. The phylogenetic composition of the Archaea assemblage was determined by cloning and then sequencing amplicons obtained from the Archaea-specific primers 21f and 958r. Sequences of 198 clones from nine samples covering three seasons and all depths grouped with marine group I Crenarchaeota (111 clones), marine group II Euryarchaeota (86 clones), and group IV Euryarchaeota (1 clone). A sequence obtained only from a DGGE band was similar to those of the marine group III Euryarchaeota.

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Béjà, Oded, Eugene V. Koonin, L. Aravind, Lance T. Taylor, Heidi Seitz, Jefferey L. Stein, Daniel C. Bensen, Robert A. Feldman, Ronald V. Swanson et Edward F. DeLong. « Comparative Genomic Analysis of Archaeal Genotypic Variants in a Single Population and in Two Different Oceanic Provinces ». Applied and Environmental Microbiology 68, n^o 1 (janvier 2002) : 335–45. http://dx.doi.org/10.1128/aem.68.1.335-345.2002.

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ABSTRACT Planktonic crenarchaeotes are present in high abundance in Antarctic winter surface waters, and they also make up a large proportion of total cell numbers throughout deep ocean waters. To better characterize these uncultivated marine crenarchaeotes, we analyzed large genome fragments from individuals recovered from a single Antarctic picoplankton population and compared them to those from a representative obtained from deeper waters of the temperate North Pacific. Sequencing and analysis of the entire DNA insert from one Antarctic marine archaeon (fosmid 74A4) revealed differences in genome structure and content between Antarctic surface water and temperate deepwater archaea. Analysis of the predicted gene products encoded by the 74A4 sequence and those derived from a temperate, deepwater planktonic crenarchaeote (fosmid 4B7) revealed many typical archaeal proteins but also several proteins that so far have not been detected in archaea. The unique fraction of marine archaeal genes included, among others, those for a predicted RNA-binding protein of the bacterial cold shock family and a eukaryote-type Zn finger protein. Comparison of closely related archaea originating from a single population revealed significant genomic divergence that was not evident from 16S rRNA sequence variation. The data suggest that considerable functional diversity may exist within single populations of coexisting microbial strains, even those with identical 16S rRNA sequences. Our results also demonstrate that genomic approaches can provide high-resolution information relevant to microbial population genetics, ecology, and evolution, even for microbes that have not yet been cultivated.

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Robertson, Charles E., John R. Spear, J. Kirk Harris et Norman R. Pace. « Diversity and Stratification of Archaea in a Hypersaline Microbial Mat ». Applied and Environmental Microbiology 75, n^o 7 (29 décembre 2008) : 1801–10. http://dx.doi.org/10.1128/aem.01811-08.

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ABSTRACT The Guerrero Negro (GN) hypersaline microbial mats have become one focus for biogeochemical studies of stratified ecosystems. The GN mats are found beneath several of a series of ponds of increasing salinity that make up a solar saltern fed from Pacific Ocean water pumped from the Laguna Ojo de Liebre near GN, Baja California Sur, Mexico. Molecular surveys of the laminated photosynthetic microbial mat below the fourth pond in the series identified an enormous diversity of bacteria in the mat, but archaea have received little attention. To determine the bulk contribution of archaeal phylotypes to the pond 4 study site, we determined the phylogenetic distribution of archaeal rRNA gene sequences in PCR libraries based on nominally universal primers. The ratios of bacterial/archaeal/eukaryotic rRNA genes, 90%/9%/1%, suggest that the archaeal contribution to the metabolic activities of the mat may be significant. To explore the distribution of archaea in the mat, sequences derived using archaeon-specific PCR primers were surveyed in 10 strata of the 6-cm-thick mat. The diversity of archaea overall was substantial albeit less than the diversity observed previously for bacteria. Archaeal diversity, mainly euryarchaeotes, was highest in the uppermost 2 to 3 mm of the mat and decreased rapidly with depth, where crenarchaeotes dominated. Only 3% of the sequences were specifically related to known organisms including methanogens. While some mat archaeal clades corresponded with known chemical gradients, others did not, which is likely explained by heretofore-unrecognized gradients. Some clades did not segregate by depth in the mat, indicating broad metabolic repertoires, undersampling, or both.

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Johnson, Benjamin W., et Boswell A. Wing. « Limited Archaean continental emergence reflected in an early Archaean 18O-enriched ocean ». Nature Geoscience 13, n^o 3 (mars 2020) : 243–48. http://dx.doi.org/10.1038/s41561-020-0538-9.

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Kendall, Brian, Christopher T. Reinhard, Timothy W. Lyons, Alan J. Kaufman, Simon W. Poulton et Ariel D. Anbar. « Pervasive oxygenation along late Archaean ocean margins ». Nature Geoscience 3, n^o 9 (22 août 2010) : 647–52. http://dx.doi.org/10.1038/ngeo942.

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Crowe, S. A., C. Jones, S. Katsev, C. Magen, A. H. O'Neill, A. Sturm, D. E. Canfield et al. « Photoferrotrophs thrive in an Archean Ocean analogue ». Proceedings of the National Academy of Sciences 105, n^o 41 (6 octobre 2008) : 15938–43. http://dx.doi.org/10.1073/pnas.0805313105.

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Busigny, Vincent, Noah J. Planavsky, Didier Jézéquel, Sean Crowe, Pascale Louvat, Julien Moureau, Eric Viollier et Timothy W. Lyons. « Iron isotopes in an Archean ocean analogue ». Geochimica et Cosmochimica Acta 133 (mai 2014) : 443–62. http://dx.doi.org/10.1016/j.gca.2014.03.004.

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Corrigan, David, Natasha Wodicka, Christopher McFarlane, Isabelle Lafrance, Deanne Van Rooyen, Daniel Bandyayera et Carl Bilodeau. « Lithotectonic Framework of the Core Zone, Southeastern Churchill Province, Canada ». Geoscience Canada 45, n^o 1 (20 avril 2018) : 1–24. http://dx.doi.org/10.12789/geocanj.2018.45.128.

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The Core Zone, a broad region located between the Superior and North Atlantic cratons and predominantly underlain by Archean gneiss and granitoid rocks, remained until recently one of the less well known parts of the Canadian Shield. Previously thought to form part of the Archean Rae Craton, and later referred to as the Southeastern Churchill Province, it has been regarded as an ancient continental block trapped between the Paleoproterozoic Torngat and New Quebec orogens, with its relationships to the adjacent Superior and North Atlantic cratons remaining unresolved. The geochronological data presented herein suggest that the Archean evolution of the Core Zone was distinct from that in both the Superior and North Atlantic (Nain) cratons. Moreover, the Core Zone itself consists of at least three distinct lithotectonic entities with different evolutions, referred to herein as the George River, Mistinibi-Raude and Falcoz River blocks, that are separated by steeply-dipping, crustal-scale shear zones interpreted as paleosutures. Specifically, the George River Block consists of ca. 2.70 Ga supracrustal rocks and associated ca. 2.70–2.57 Ga intrusions. The Mistinibi-Raude Block consists of remnants of a ca. 2.37 Ga volcanic arc intruded by a ca. 2.32 Ga arc plutonic suite (Pallatin) and penecontemporaneous alkali plutons (Pelland and Nekuashu suites). It also hosts a coarse clastic cover sequence (the Hutte Sauvage Group) which contains detrital zircons provided from locally-derived, ca. 2.57–2.50 Ga, 2.37–2.32 Ga, and 2.10–2.08 Ga sources, with the youngest concordant grain dated at 1987 ± 7 Ma. The Falcoz River Block consists of ca. 2.89–2.80 Ga orthogneiss intruded by ca. 2.74–2.70 granite, tonalite, and granodiorite. At the western margin of the Core Zone, the George River Block and Kuujjuaq Domain may have been proximal by ca. 1.84 Ga as both appear to have been sutured by the 1.84–1.82 Ga De Pas Batholith, whereas at its eastern margin, the determination of metamorphic ages of ca. 1.85 to 1.80 Ga in the Falcoz River Block suggests protracted interaction with the adjacent Lac Lomier Complex during their amalgamation and suturing, but with a younger, ‘New Quebec’ overprint as well. The three crustal blocks forming the Core Zone add to a growing list of ‘exotic’ Archean to earliest Paleoproterozoic microcontinents and crustal slices that extend around the Superior Craton from the Grenville Front through Hudson Strait, across Hudson Bay and into Manitoba and Saskatchewan, in what was the Manikewan Ocean realm, which closed between ca. 1.83–1.80 Ga during the formation of supercontinent Nuna.RÉSUMÉLa Zone noyau, une vaste région située entre les cratons du Supérieur et de l’Atlantique Nord et reposant principalement sur des gneiss archéens et des roches granitiques, est demeurée jusqu’à récemment l’une des parties les moins bien connues du Bouclier canadien. Considérée auparavant comme faisant partie du craton archéen de Rae, puis comme la portion sud-est de la Province de Churchill, on l’a perçue comme un ancien bloc continental piégé entre les orogènes paléoprotérozoïques des Torngat et du Nouveau-Québec, ses relations avec les cratons supérieurs adjacents et de l’Atlantique Nord demeurant nébuleuses. Les données géochronologiques présentées ici permettent de penser que l’évolution archéenne de la Zone noyau a été différente de celle des cratons du Supérieur et de l’Atlantique Nord (Nain). De plus, la Zone noyau elle-même se compose d’au moins trois entités lithotectoniques distinctes avec des évolutions différentes, appelées ici les blocs de la rivière George, de Mistinibi-Raude et de la rivière Falcoz, lesquels sont séparées par des zones de cisaillement crustales à forte inclinaison, conçues comme des paléosutures. Plus précisément, le bloc de la rivière George est constitué de roches supracrustales d'env. 2,70 Ga, et d’intrusions connexes d'env. 2,70–2,57 Ga. Le bloc Mistinibi-Raude est constitué de vestiges d’un arc volcanique d'env. 2,37 Ga, recoupé par une suite plutonique d’arc d'env. 2,32 Ga (Pallatin) et de plutons alcalins péné-contemporains (suites Pelland et Nekuashu). Il contient également une séquence de couverture clastique grossière (le groupe Hutte Sauvage) renfermant des zircons détritiques de sources locales, âgés d'env. 2,57–2,50 Ga, 2,37–2,32 Ga et 2,10–2,08 Ga, le grain concordant le plus jeune étant âgé de 1987 ± 7 Ma. Le bloc de la rivière Falcoz est formé d’un orthogneiss âgé d'env. 2,89–2,80 Ga, recoupé par des intrusions de granite, tonalite et granodiorite âgées d'env. 2,74–2,70 Ga. À la marge ouest de la Zone noyau, le bloc de la rivière George et du domaine de Kuujjuaq peuvent avoir été proximaux il y a 1,84 Ga env., car les deux semblent avoir été suturés par le batholithe De Pas il y a environ 1,84–1,82 Ga, alors qu’à sa marge est, la détermination des datations métamorphiques de 1,85 à 1,80 Ga dans le bloc de la rivière Falcoz suggère une interaction prolongée avec le complexe adjacent du lac Lomier durant leur amalgamation et leur suture, mais affecté aussi d’une surimpression « Nouveau Québec » plus jeune. Les trois blocs crustaux formant la Zone noyau s’ajoutent à une liste croissante de micro-continents et d’écailles crustales « exotiques » archéennes à paléoprotérozoïques très précoces qui s’étalent autour du craton Supérieur depuis le front de Grenville jusqu’au Manitoba, à travers le détroit d’Hudson, la baie d’Hudson jusque dans le Manitoba et la Saskatchewan, là où s’étendait l’océan Manikewan, lequel s’est refermé il y a environ 1,83–1,80 Ga, pendant la formation du supercontinent Nuna.

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Ouverney, Cleber C., et Jed A. Fuhrman. « Marine Planktonic Archaea Take Up Amino Acids ». Applied and Environmental Microbiology 66, n^o 11 (1 novembre 2000) : 4829–33. http://dx.doi.org/10.1128/aem.66.11.4829-4833.2000.

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ABSTRACT Archaea are traditionally thought of as “extremophiles,” but recent studies have shown that marine planktonic Archaea make up a surprisingly large percentage of ocean midwater microbial communities, up to 60% of the total prokaryotes. However, the basic physiology and contribution of Archaea to community microbial activity remain unknown. We have studied Archaea from 200-m depths of the northwest Mediterranean Sea and the Pacific Ocean near California, measuring the archaeal activity under simulated natural conditions (8 to 17°C, dark and anaerobic) by means of a method called substrate tracking autoradiography fluorescence in situ hybridization (STARFISH) that simultaneously detects specific cell types by 16S rRNA probe binding and activity by microautoradiography. In the 200-m-deep Mediterranean and Pacific samples, cells binding the archaeal probes made up about 43 and 14% of the total countable cells, respectively. Our results showed that the Archaea are active in the uptake of dissolved amino acids from natural concentrations (nanomolar) with about 60% of the individuals in the archaeal communities showing measurable uptake. Bacteria showed a similar proportion of active cells. We concluded that a portion of these Archaea is heterotrophic and also appears to coexist successfully with Bacteria in the same water.

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Harrison, C. G. A. « Constraints on ocean volume change since the Archean ». Geophysical Research Letters 26, n^o 13 (1 juillet 1999) : 1913–16. http://dx.doi.org/10.1029/1999gl900425.

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Habicht, K. S. « Calibration of Sulfate Levels in the Archean Ocean ». Science 298, n^o 5602 (20 décembre 2002) : 2372–74. http://dx.doi.org/10.1126/science.1078265.

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Henderson-Sellers, B., et A. Henderson-Sellers. « Modelling the ocean climate for the early archaean ». Palaeogeography, Palaeoclimatology, Palaeoecology 75, n^o 3 (août 1989) : 195–221. http://dx.doi.org/10.1016/0031-0182(89)90177-6.

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Busigny, Vincent, Oanez Lebeau, Magali Ader, Bryan Krapež et Andrey Bekker. « Nitrogen cycle in the Late Archean ferruginous ocean ». Chemical Geology 362 (décembre 2013) : 115–30. http://dx.doi.org/10.1016/j.chemgeo.2013.06.023.

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Henderson-Sellers, B., et A. Henderson-Sellers. « Modelling the ocean climate for the early archaean ». Global and Planetary Change 1, n^o 3 (août 1989) : 195–221. http://dx.doi.org/10.1016/0921-8181(89)90003-9.

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Sharma, S. Das, D. J. Patil, R. Srinivasan et K. Gopalan. « Very high18o enrichment in Archean cherts from South India : implications for Archean ocean temperature ». Terra Nova 6, n^o 4 (juillet 1994) : 385–90. http://dx.doi.org/10.1111/j.1365-3121.1994.tb00511.x.

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Callieri, Cristiana, Gianluca Corno, Emanuele Caravati, Serena Rasconi, Mario Contesini et Roberto Bertoni. « Bacteria, Archaea, and Crenarchaeota in the Epilimnion and Hypolimnion of a Deep Holo-Oligomictic Lake ». Applied and Environmental Microbiology 75, n^o 22 (18 septembre 2009) : 7298–300. http://dx.doi.org/10.1128/aem.01231-09.

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ABSTRACT In a deep, subalpine holo-oligomictic lake, the relative abundance of Archaea and Crenarchaeota, but not that of Bacteria, increases significantly with depth and varies seasonally. Cell-specific prokaryotic productivity is homogeneous along the water column. The concept of active Archaea observed in the deep ocean can therefore be extended to a deep oxic lake.

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Vik, Dean R., Simon Roux, Jennifer R. Brum, Ben Bolduc, Joanne B. Emerson, Cory C. Padilla, Frank J. Stewart et Matthew B. Sullivan. « Putative archaeal viruses from the mesopelagic ocean ». PeerJ 5 (15 juin 2017) : e3428. http://dx.doi.org/10.7717/peerj.3428.

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Oceanic viruses that infect bacteria, or phages, are known to modulate host diversity, metabolisms, and biogeochemical cycling, while the viruses that infect marine Archaea remain understudied despite the critical ecosystem roles played by their hosts. Here we introduce “MArVD”, for Metagenomic Archaeal Virus Detector, an annotation tool designed to identify putative archaeal virus contigs in metagenomic datasets. MArVD is made publicly available through the online iVirus analytical platform. Benchmarking analysis of MArVD showed it to be >99% accurate and 100% sensitive in identifying the 127 known archaeal viruses among the 12,499 viruses in the VirSorter curated dataset. Application of MArVD to 10 viral metagenomes from two depth profiles in the Eastern Tropical North Pacific (ETNP) oxygen minimum zone revealed 43 new putative archaeal virus genomes and large genome fragments ranging in size from 10 to 31 kb. Network-based classifications, which were consistent with marker gene phylogenies where available, suggested that these putative archaeal virus contigs represented six novel candidate genera. Ecological analyses, via fragment recruitment and ordination, revealed that the diversity and relative abundances of these putative archaeal viruses were correlated with oxygen concentration and temperature along two OMZ-spanning depth profiles, presumably due to structuring of the host Archaea community. Peak viral diversity and abundances were found in surface waters, whereThermoplasmata16S rRNA genes are prevalent, suggesting these archaea as hosts in the surface habitats. Together these findings provide a baseline for identifying archaeal viruses in sequence datasets, and an initial picture of the ecology of such viruses in non-extreme environments.

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Mehta, Mausmi P., David A. Butterfield et John A. Baross. « Phylogenetic Diversity of Nitrogenase (nifH) Genes in Deep-Sea and Hydrothermal Vent Environments of the Juan de Fuca Ridge ». Applied and Environmental Microbiology 69, n^o 2 (février 2003) : 960–70. http://dx.doi.org/10.1128/aem.69.2.960-970.2003.

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ABSTRACT The subseafloor microbial habitat associated with typical unsedimented mid-ocean-ridge hydrothermal vent ecosystems may be limited by the availability of fixed nitrogen, inferred by the low ammonium and nitrate concentrations measured in diffuse hydrothermal fluid. Dissolved N2 gas, the largest reservoir of nitrogen in the ocean, is abundant in deep-sea and hydrothermal vent fluid. In order to test the hypothesis that biological nitrogen fixation plays an important role in nitrogen cycling in the subseafloor associated with unsedimented hydrothermal vents, degenerate PCR primers were designed to amplify the nitrogenase iron protein gene nifH from hydrothermal vent fluid. A total of 120 nifH sequences were obtained from four samples: a nitrogen-poor diffuse vent named marker 33 on Axial Volcano, sampled twice over a period of 1 year as its temperature decreased; a nitrogen-rich diffuse vent near Puffer on Endeavour Segment; and deep seawater with no detectable hydrothermal plume signal. Subseafloor nifH genes from marker 33 and Puffer are related to anaerobic clostridia and sulfate reducers. Other nifH genes unique to the vent samples include proteobacteria and divergent Archaea. All of the nifH genes from the deep-seawater sample are most closely related to the thermophilic, anaerobic archaeon Methanococcus thermolithotrophicus (77 to 83% amino acid similarity). These results provide the first genetic evidence of potential nitrogen fixers in hydrothermal vent environments and indicate that at least two sources contribute to the diverse assemblage of nifH genes detected in hydrothermal vent fluid: nifH genes from an anaerobic, hot subseafloor and nifH genes from cold, oxygenated deep seawater.

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Avila-Alonso, Dailé, Jan M. Baetens, Rolando Cardenas et Bernard De Baets. « Assessing the effects of ultraviolet radiation on the photosynthetic potential in Archean marine environments ». International Journal of Astrobiology 16, n^o 3 (9 septembre 2016) : 271–79. http://dx.doi.org/10.1017/s147355041600032x.

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AbstractIn this work, the photosynthesis model presented by Avilaet al. in 2013 is extended and more scenarios inhabited by ancient cyanobacteria are investigated to quantify the effects of ultraviolet (UV) radiation on their photosynthetic potential in marine environments of the Archean eon. We consider ferrous ions as blockers of UV during the Early Archean, while the absorption spectrum of chlorophyllais used to quantify the fraction of photosynthetically active radiation absorbed by photosynthetic organisms. UV could have induced photoinhibition at the water surface, thereby strongly affecting the species with low light use efficiency. A higher photosynthetic potential in early marine environments was shown than in the Late Archean as a consequence of the attenuation of UVC and UVB by iron ions, which probably played an important role in the protection of ancient free-floating bacteria from high-intensity UV radiation. Photosynthetic organisms in Archean coastal and ocean environments were probably abundant in the first 5 and 25 m of the water column, respectively. However, species with a relatively high efficiency in the use of light could have inhabited ocean waters up to a depth of 200 m and show a Deep Chlorophyll Maximum near 60 m depth. We show that the electromagnetic radiation from the Sun, both UV and visible light, could have determined the vertical distribution of Archean marine photosynthetic organisms.

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Krissansen-Totton, Joshua, Giada N. Arney et David C. Catling. « Constraining the climate and ocean pH of the early Earth with a geological carbon cycle model ». Proceedings of the National Academy of Sciences 115, n^o 16 (2 avril 2018) : 4105–10. http://dx.doi.org/10.1073/pnas.1721296115.

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The early Earth’s environment is controversial. Climatic estimates range from hot to glacial, and inferred marine pH spans strongly alkaline to acidic. Better understanding of early climate and ocean chemistry would improve our knowledge of the origin of life and its coevolution with the environment. Here, we use a geological carbon cycle model with ocean chemistry to calculate self-consistent histories of climate and ocean pH. Our carbon cycle model includes an empirically justified temperature and pH dependence of seafloor weathering, allowing the relative importance of continental and seafloor weathering to be evaluated. We find that the Archean climate was likely temperate (0–50 °C) due to the combined negative feedbacks of continental and seafloor weathering. Ocean pH evolves monotonically from 6.6−0.4+0.6 (2σ) at 4.0 Ga to 7.0−0.5+0.7 (2σ) at the Archean–Proterozoic boundary, and to 7.9−0.2+0.1 (2σ) at the Proterozoic–Phanerozoic boundary. This evolution is driven by the secular decline of pCO2, which in turn is a consequence of increasing solar luminosity, but is moderated by carbonate alkalinity delivered from continental and seafloor weathering. Archean seafloor weathering may have been a comparable carbon sink to continental weathering, but is less dominant than previously assumed, and would not have induced global glaciation. We show how these conclusions are robust to a wide range of scenarios for continental growth, internal heat flow evolution and outgassing history, greenhouse gas abundances, and changes in the biotic enhancement of weathering.

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Meador, Travis B., Niels Schoffelen, Timothy G. Ferdelman, Osmond Rebello, Alexander Khachikyan et Martin Könneke. « Carbon recycling efficiency and phosphate turnover by marine nitrifying archaea ». Science Advances 6, n^o 19 (mai 2020) : eaba1799. http://dx.doi.org/10.1126/sciadv.aba1799.

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Thaumarchaeotal nitrifiers are among the most abundant organisms in the ocean, but still unknown is the carbon (C) yield from nitrification and the coupling of these fluxes to phosphorus (P) turnover and release of metabolites from the cell. Using a dual radiotracer approach, we found that Nitrosopumilus maritimus fixed roughly 0.3 mol C, assimilated 2 mmol P, and released ca. 10−2 mol C and 10−5 mol P as dissolved organics (DOC and DOP) per mole ammonia respired. Phosphate turnover may influence assimilation fluxes by nitrifiers in the euphotic zone, which parallel those of the dark ocean. Collectively, marine nitrifiers assimilate up to 2 Pg C year−1 and 0.05 Pg P year−1 and thereby recycle roughly 5% of mineralized C and P into marine biomass. Release of roughly 50 Tg DOC and 0.2 Tg DOP by thaumarchaea each year represents a small but fresh input of reduced substrates throughout the ocean.

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Loescher, C. R., A. Kock, M. Koenneke, J. LaRoche, H. W. Bange et R. A. Schmitz. « Production of oceanic nitrous oxide by ammonia-oxidizing archaea ». Biogeosciences Discussions 9, n^o 2 (23 février 2012) : 2095–122. http://dx.doi.org/10.5194/bgd-9-2095-2012.

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Abstract. The recent finding that microbial ammonia oxidation in the ocean is performed by archaea to a greater extent than by bacteria has drastically changed the view on oceanic nitrification. The numerical dominance of archaeal ammonia-oxidizers (AOA) over their bacterial counterparts (AOB) in large parts of the ocean leads to the hypothesis that AOA rather than AOB could be the key organisms for the oceanic production of the strong greenhouse gas nitrous oxide (N2O) which occurs as a by-product of nitrification. Very recently, enrichment cultures of marine ammonia-oxidizing archaea have been described to produce N2O. Here, we demonstrate that archaeal ammonia monooxygenase genes (amoA) were detectable throughout the water column of the Eastern Tropical North Atlantic (ETNA) and Eastern Tropical South Pacific Oceans (ETSP). Particularly in the ETNA, maxima in abundance and expression of archaeal amoA genes correlated with the N2O maximum and the oxygen minimum, whereas the abundances of bacterial amoA genes were negligible. Moreover, selective inhibition of archaea in seawater incubations from the ETNA decreased the N2O production significantly. In studies with the only cultivated marine archaeal ammonia-oxidizer Nitrosopumilus maritimus SCM1, we provide the first direct evidence for N2O production in a pure culture of AOA, excluding the involvement of other microorganisms as possibly present in enrichments. N. maritimus showed high N2O production rates under low oxygen concentrations comparable to concentrations existing in the oxycline of the ETNA, whereas the N2O production from two AOB cultures was comparably low under similar conditions. Based on our findings, we hypothesize that the production of N2O in tropical ocean areas results mainly from archaeal nitrification and will be affected by the predicted decrease in dissolved oxygen in the ocean.

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Löscher, C. R., A. Kock, M. Könneke, J. LaRoche, H. W. Bange et R. A. Schmitz. « Production of oceanic nitrous oxide by ammonia-oxidizing archaea ». Biogeosciences 9, n^o 7 (4 juillet 2012) : 2419–29. http://dx.doi.org/10.5194/bg-9-2419-2012.

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Abstract. The recent finding that microbial ammonia oxidation in the ocean is performed by archaea to a greater extent than by bacteria has drastically changed the view on oceanic nitrification. The numerical dominance of archaeal ammonia-oxidizers (AOA) over their bacterial counterparts (AOB) in large parts of the ocean leads to the hypothesis that AOA rather than AOB could be the key organisms for the oceanic production of the strong greenhouse gas nitrous oxide (N2O) that occurs as a by-product of nitrification. Very recently, enrichment cultures of marine ammonia-oxidizing archaea have been reported to produce N2O. Here, we demonstrate that archaeal ammonia monooxygenase genes (amoA) were detectable throughout the water column of the eastern tropical North Atlantic (ETNA) and eastern tropical South Pacific (ETSP) Oceans. Particularly in the ETNA, comparable patterns of abundance and expression of archaeal amoA genes and N2O co-occurred in the oxygen minimum, whereas the abundances of bacterial amoA genes were negligible. Moreover, selective inhibition of archaea in seawater incubations from the ETNA decreased the N2O production significantly. In studies with the only cultivated marine archaeal ammonia-oxidizer Nitrosopumilus maritimus SCM1, we provide the first direct evidence for N2O production in a pure culture of AOA, excluding the involvement of other microorganisms as possibly present in enrichments. N. maritimus showed high N2O production rates under low oxygen concentrations comparable to concentrations existing in the oxycline of the ETNA, whereas the N2O production from two AOB cultures was comparably low under similar conditions. Based on our findings, we hypothesize that the production of N2O in tropical ocean areas results mainly from archaeal nitrification and will be affected by the predicted decrease in dissolved oxygen in the ocean.

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Olson, Haley C., Nadja Drabon et David T. Johnston. « Oxygen isotope insights into the Archean ocean and atmosphere ». Earth and Planetary Science Letters 591 (août 2022) : 117603. http://dx.doi.org/10.1016/j.epsl.2022.117603.

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Kitajima, K., S. Maruyama, S. Utsunomiya et J. G. Liou. « Seafloor hydrothermal alteration at an Archaean mid-ocean ridge ». Journal of Metamorphic Geology 19, n^o 5 (septembre 2001) : 583–99. http://dx.doi.org/10.1046/j.0263-4929.2001.00330.x.

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Herndl, Gerhard J., Thomas Reinthaler, Eva Teira, Hendrik van Aken, Cornelius Veth, Annelie Pernthaler et Jakob Pernthaler. « Contribution of Archaea to Total Prokaryotic Production in the Deep Atlantic Ocean ». Applied and Environmental Microbiology 71, n^o 5 (mai 2005) : 2303–9. http://dx.doi.org/10.1128/aem.71.5.2303-2309.2005.

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ABSTRACT Fluorescence in situ hybridization (FISH) in combination with polynucleotide probes revealed that the two major groups of planktonic Archaea (Crenarchaeota and Euryarchaeota) exhibit a different distribution pattern in the water column of the Pacific subtropical gyre and in the Antarctic Circumpolar Current system. While Euryarchaeota were found to be more dominant in nearsurface waters, Crenarchaeota were relatively more abundant in the mesopelagic and bathypelagic waters. We determined the abundance of archaea in the mesopelagic and bathypelagic North Atlantic along a south-north transect of more than 4,000 km. Using an improved catalyzed reporter deposition-FISH (CARD-FISH) method and specific oligonucleotide probes, we found that archaea were consistently more abundant than bacteria below a 100-m depth. Combining microautoradiography with CARD-FISH revealed a high fraction of metabolically active cells in the deep ocean. Even at a 3,000-m depth, about 16% of the bacteria were taking up leucine. The percentage of Euryarchaeota and Crenarchaeaota taking up leucine did not follow a specific trend, with depths ranging from 6 to 35% and 3 to 18%, respectively. The fraction of Crenarchaeota taking up inorganic carbon increased with depth, while Euryarchaeota taking up inorganic carbon decreased from 200 m to 3,000 m in depth. The ability of archaea to take up inorganic carbon was used as a proxy to estimate archaeal cell production and to compare this archaeal production with total prokaryotic production measured via leucine incorporation. We estimate that archaeal production in the mesopelagic and bathypelagic North Atlantic contributes between 13 to 27% to the total prokaryotic production in the oxygen minimum layer and 41 to 84% in the Labrador Sea Water, declining to 10 to 20% in the North Atlantic Deep Water. Thus, planktonic archaea are actively growing in the dark ocean although at lower growth rates than bacteria and might play a significant role in the oceanic carbon cycle.

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Sleep, Norman H. « Archean plate tectonics : what can be learned from continental geology ? » Canadian Journal of Earth Sciences 29, n^o 10 (1 octobre 1992) : 2066–71. http://dx.doi.org/10.1139/e92-164.

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Some basic questions about Archean plate tectonics can be addressed by examining accretionary Archean margins, in particular fault zones with significant strike-slip components on the Canadian Shield. (1) Were the oceanic plates typically rigid like modern plates? Yes. Significant lateral viscosity contrasts in the lithosphere between plates and plate boundaries are required for major strike-slip faults to exist. Conversely, strike-slip faults are a kinematic consequence of rigid plates. (2) Did large oceanic plates exist in the Archean? Probably. First, the length and offset of the longest preserved segments of Archean faults are similar to modern examples such as in Alaska. Less directly, the duration of a period with a consistent sense of strike slip at a point on the continental side of an accretionary margin should be related to the time that a typical oceanic plate remains outboard of the margin. This time varies proportionally with size of typical ocean plates and inversely with their velocity. The duration of an example of persistent strike slip on the Canadian Shield is comparable to that of Cenozoic examples. (3) Did old oceanic crust and hence moderate plate velocities occur in the Archean? Perhaps. Paleomagnetic poles are the most direct line of evidence, but they usually relate to continental blocks. The duration of consistent strike-slip motion, preserved alkalic seamounts which record eruption on old oceanic crust, and the duration of ocean basins are potential indirect indications. Overall, the hotter mantle does not appear to have had a great effect on Archean plate motions. Thus, the geometry and rate of plate tectonics are strongly influenced by the lithosphere.

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Kienert, H., G. Feulner et V. Petoukhov. « Albedo and heat transport in 3-D model simulations of the early Archean climate ». Climate of the Past 9, n^o 4 (7 août 2013) : 1841–62. http://dx.doi.org/10.5194/cp-9-1841-2013.

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Abstract. At the beginning of the Archean eon (ca. 3.8 billion years ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics) to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

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Teira, Eva, Thomas Reinthaler, Annelie Pernthaler, Jakob Pernthaler et Gerhard J. Herndl. « Combining Catalyzed Reporter Deposition-Fluorescence In Situ Hybridization and Microautoradiography To Detect Substrate Utilization by Bacteria and Archaea in the Deep Ocean ». Applied and Environmental Microbiology 70, n^o 7 (juillet 2004) : 4411–14. http://dx.doi.org/10.1128/aem.70.7.4411-4414.2004.

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ABSTRACT The recently developed CARD-FISH protocol was refined for the detection of marine Archaea by replacing the lysozyme permeabilization treatment with proteinase K. This modification resulted in about twofold-higher detection rates for Archaea in deep waters. Using this method in combination with microautoradiography, we found that Archaea are more abundant than Bacteria (42% versus 32% of 4′,6′-diamidino-2-phenylindole counts) in the deep waters of the North Atlantic and that a larger fraction of Archaea than of Bacteria takes up l-aspartic acid (19% versus 10%).

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DeLong, Edward. « Microbial Domains in the Ocean : A Lesson from the Archaea ». Oceanography 20, n^o 2 (1 juin 2007) : 124–29. http://dx.doi.org/10.5670/oceanog.2007.56.

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Gifford, Jennifer N., Shawn J. Malone et Paul A. Mueller. « The Medicine Hat Block and the Early Paleoproterozoic Assembly of Western Laurentia ». Geosciences 10, n^o 7 (15 juillet 2020) : 271. http://dx.doi.org/10.3390/geosciences10070271.

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The accretion of the Wyoming, Hearne, and Superior Provinces to form the Archean core of western Laurentia occurred rapidly in the Paleoproterozoic. Missing from Hoffman’s (1988) original rapid aggregation model was the Medicine Hat block (MHB). The MHB is a structurally distinct, complex block of Precambrian crystalline crust located between the Archean Wyoming Craton and the Archean Hearne Province and overlain by an extensive Phanerozoic cover. It is distinguished on the basis of geophysical evidence and limited geochemical data from crustal xenoliths and drill core. New U-Pb ages and Lu-Hf data from zircons reveal protolith crystallization ages from 2.50 to 3.28 Ga, magmatism/metamorphism at 1.76 to 1.81 Ga, and εHfT values from −23.3 to 8.5 in the Archean and Proterozoic rocks of the MHB. These data suggest that the MHB played a pivotal role in the complex assembly of western Laurentia in the Paleoproterozoic as a conjugate or extension to the Montana Metasedimentary Terrane (MMT) of the northwestern Wyoming Province. This MMT–MHB connection likely existed in the Mesoarchean, but it was broken sometime during the earliest Paleoproterozoic with the formation and closure of a small ocean basin. Closure of the ocean led to formation of the Little Belt arc along the southern margin of the MHB beginning at approximately 1.9 Ga. The MHB and MMT re-joined at this time as they amalgamated into the supercontinent Laurentia during the Great Falls orogeny (1.7–1.9 Ga), which formed the Great Falls tectonic zone (GFTZ). The GFTZ developed in the same timeframe as the better-known Trans-Hudson orogen to the east that marks the merger of the Wyoming, Hearne, and Superior Provinces, which along with the MHB, formed the Archean core of western Laurentia.

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Kienert, H., G. Feulner et V. Petoukhov. « Albedo and heat transport in 3-dimensional model simulations of the early Archean climate ». Climate of the Past Discussions 9, n^o 1 (24 janvier 2013) : 525–82. http://dx.doi.org/10.5194/cpd-9-525-2013.

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Abstract. At the beginning of the Archean eon (ca. 3.8 billion yr ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun problem" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-dimensional model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterisation of the ice-albedo feedback for 1-dimensional model simulations of the early Archean and thus the faint young Sun problem.

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Santoro, Alyson E., Christopher L. Dupont, R. Alex Richter, Matthew T. Craig, Paul Carini, Matthew R. McIlvin, Youngik Yang, William D. Orsi, Dawn M. Moran et Mak A. Saito. « Genomic and proteomic characterization of “CandidatusNitrosopelagicus brevis” : An ammonia-oxidizing archaeon from the open ocean ». Proceedings of the National Academy of Sciences 112, n^o 4 (13 janvier 2015) : 1173–78. http://dx.doi.org/10.1073/pnas.1416223112.

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Thaumarchaeota are among the most abundant microbial cells in the ocean, but difficulty in cultivating marine Thaumarchaeota has hindered investigation into the physiological and evolutionary basis of their success. We report here a closed genome assembled from a highly enriched culture of the ammonia-oxidizing pelagic thaumarchaeon CN25, originating from the open ocean. The CN25 genome exhibits strong evidence of genome streamlining, including a 1.23-Mbp genome, a high coding density, and a low number of paralogous genes. Proteomic analysis recovered nearly 70% of the predicted proteins encoded by the genome, demonstrating that a high fraction of the genome is translated. In contrast to other minimal marine microbes that acquire, rather than synthesize, cofactors, CN25 encodes and expresses near-complete biosynthetic pathways for multiple vitamins. Metagenomic fragment recruitment indicated the presence of DNA sequences >90% identical to the CN25 genome throughout the oligotrophic ocean. We propose the provisional name “CandidatusNitrosopelagicus brevis” str. CN25 for this minimalist marine thaumarchaeon and suggest it as a potential model system for understanding archaeal adaptation to the open ocean.

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Rey, Patrice F., Nicolas Coltice et Nicolas Flament. « Archean Geodynamics Underneath Weak, Flat, and Flooded Continents ». Elements 20, n^o 3 (1 juin 2024) : 180–86. http://dx.doi.org/10.2138/gselements.20.3.180.

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Although a significant volume of crust was extracted from the mantle early in Earth’s history, the contribution of felsic rocks to the sedimentary record was minimal until ~3.0 Ga. On a hotter Earth, this conundrum dissipates if we consider that the felsic crust was buried under thick basaltic covers, continents were flooded by a near-global ocean, and the crust was too weak to sustain high mountains, making it largely unavailable to erosion. Gravitational forces destabilized basaltic covers within these weak, flat, and flooded continents, driving intra-crustal tectonics and forcing episodic subduction at the edges of continents. Through secular cooling, this dual-mode geodynamics progressively transitioned to plate tectonics.

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Chaban, Bonnie, Sandy Y. M. Ng et Ken F. Jarrell. « Archaeal habitats — from the extreme to the ordinary ». Canadian Journal of Microbiology 52, n^o 2 (1 février 2006) : 73–116. http://dx.doi.org/10.1139/w05-147.

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The domain Archaea represents a third line of evolutionary descent, separate from Bacteria and Eucarya. Initial studies seemed to limit archaea to various extreme environments. These included habitats at the extreme limits that allow life on earth, in terms of temperature, pH, salinity, and anaerobiosis, which were the homes to hyper thermo philes, extreme (thermo)acidophiles, extreme halophiles, and methanogens. Typical environments from which pure cultures of archaeal species have been isolated include hot springs, hydrothermal vents, solfataras, salt lakes, soda lakes, sewage digesters, and the rumen. Within the past two decades, the use of molecular techniques, including PCR-based amplification of 16S rRNA genes, has allowed a culture-independent assessment of microbial diversity. Remarkably, such techniques have indicated a wide distribution of mostly uncultured archaea in normal habitats, such as ocean waters, lake waters, and soil. This review discusses organisms from the domain Archaea in the context of the environments where they have been isolated or detected. For organizational purposes, the domain has been separated into the traditional groups of methanogens, extreme halophiles, thermoacidophiles, and hyperthermophiles, as well as the uncultured archaea detected by molecular means. Where possible, we have correlated known energy-yielding reactions and carbon sources of the archaeal types with available data on potential carbon sources and electron donors and acceptors present in the environments. From the broad distribution, metabolic diversity, and sheer numbers of archaea in environments from the extreme to the ordinary, the roles that the Archaea play in the ecosystems have been grossly underestimated and are worthy of much greater scrutiny.Key words: Archaea, methanogen, extreme halophile, hyperthermophile, thermoacidophile, uncultured archaea, habitats.

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Le Hir, G., Y. Teitler, F. Fluteau, Y. Donnadieu et P. Philippot. « The faint young Sun problem revisited with a 3-D climate–carbon model – Part 1 ». Climate of the Past 10, n^o 2 (3 avril 2014) : 697–713. http://dx.doi.org/10.5194/cp-10-697-2014.

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Abstract. During the Archaean, the Sun's luminosity was 18 to 25% lower than the present day. One-dimensional radiative convective models (RCM) generally infer that high concentrations of greenhouse gases (CO2, CH4) are required to prevent the early Earth's surface temperature from dropping below the freezing point of liquid water and satisfying the faint young Sun paradox (FYSP, an Earth temperature at least as warm as today). Using a one-dimensional (1-D) model, it was proposed in 2010 that the association of a reduced albedo and less reflective clouds may have been responsible for the maintenance of a warm climate during the Archaean without requiring high concentrations of atmospheric CO2 (pCO2). More recently, 3-D climate simulations have been performed using atmospheric general circulation models (AGCM) and Earth system models of intermediate complexity (EMIC). These studies were able to solve the FYSP through a large range of carbon dioxide concentrations, from 0.6 bar with an EMIC to several millibars with AGCMs. To better understand this wide range in pCO2, we investigated the early Earth climate using an atmospheric GCM coupled to a slab ocean. Our simulations include the ice-albedo feedback and specific Archaean climatic factors such as a faster Earth rotation rate, high atmospheric concentrations of CO2 and/or CH4, a reduced continental surface, a saltier ocean, and different cloudiness. We estimated full glaciation thresholds for the early Archaean and quantified positive radiative forcing required to solve the FYSP. We also demonstrated why RCM and EMIC tend to overestimate greenhouse gas concentrations required to avoid full glaciations or solve the FYSP. Carbon cycle–climate interplays and conditions for sustaining pCO2 will be discussed in a companion paper.

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Murray, AE, KY Wu, CL Moyer, DM Karl et EF DeLong. « Evidence for circumpolar distribution of planktonic Archaea in the Southern Ocean ». Aquatic Microbial Ecology 18 (1999) : 263–73. http://dx.doi.org/10.3354/ame018263.

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Godfrey, Linda V., et Paul G. Falkowski. « The cycling and redox state of nitrogen in the Archaean ocean ». Nature Geoscience 2, n^o 10 (13 septembre 2009) : 725–29. http://dx.doi.org/10.1038/ngeo633.

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Pasek, M. A., J. P. Harnmeijer, R. Buick, M. Gull et Z. Atlas. « Evidence for reactive reduced phosphorus species in the early Archean ocean ». Proceedings of the National Academy of Sciences 110, n^o 25 (3 juin 2013) : 10089–94. http://dx.doi.org/10.1073/pnas.1303904110.

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Shibuya, Takazo, Tsuyoshi Komiya, Kentaro Nakamura, Ken Takai et Shigenori Maruyama. « Highly alkaline, high-temperature hydrothermal fluids in the early Archean ocean ». Precambrian Research 182, n^o 3 (1 octobre 2010) : 230–38. http://dx.doi.org/10.1016/j.precamres.2010.08.011.

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Rouxel, O. J. « Iron Isotope Constraints on the Archean and Paleoproterozoic Ocean Redox State ». Science 307, n^o 5712 (18 février 2005) : 1088–91. http://dx.doi.org/10.1126/science.1105692.

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Zhang, Chuanlun L., Ann Pearson, Yi-Liang Li, Gary Mills et Juergen Wiegel. « Thermophilic Temperature Optimum for Crenarchaeol Synthesis and Its Implication for Archaeal Evolution ». Applied and Environmental Microbiology 72, n^o 6 (juin 2006) : 4419–22. http://dx.doi.org/10.1128/aem.00191-06.

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ABSTRACT The isoprenoid lipid crenarchaeol is widespread in hot springs of California and Nevada. Terrestrial and marine data together suggest a maximum relative abundance of crenarchaeol at ∼40ï¿½C. This warm temperature optimum may have facilitated colonization of the ocean by (hyper)thermophilic Archaea and the major marine radiation of Crenarchaeota.

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Rollinson, H. R. « Early basic magmatism in the evolution of Archaean high-grade gneiss terrains : an example from the Lewisian of NW Scotland ». Mineralogical Magazine 51, n^o 361 (septembre 1987) : 345–55. http://dx.doi.org/10.1180/minmag.1987.051.361.02.

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AbstractAmphibolite blocks from an Archaean (2.9 Ga) trondhjemite-agmatite complex in the Lewisian at Gruinard Bay have a varied trace element and REE content. Whilst some of the variability is attributable to element mobility during high-grade metamorphism and subsequent trondhjemite magmatism, it is for the main part considered to be a primary feature of the amphibolites. The observed trace element and REE chemistry is best explained in terms of source region heterogeneity and suggests a melting regime comparable with that beneath certain types of mid-ocean ridge. There are geochemical similarities between the amphibolites and the Lewisian layered gabbro-ultramafic complexes, and the two may represent the derivative liquid and associated cumulates respectively from a common parent magma. Thus there is a parallel between the processes which generated some Archaean amphibolites and layered gabbro complexes and those operating beneath modern ocean ridges. Hornblendite and amphibolite pods enclosed within tonalitic gneiss, also found as blocks in the agmatite complex, are geochemically distinct from the main group of amphibolites and are probably of calc-alkaline parentage.

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Dey, S., et J. F. Moyen. « About this title - Archean Granitoids of India : Windows into Early Earth Tectonics ». Geological Society, London, Special Publications 489, n^o 1 (2020) : NP. http://dx.doi.org/10.1144/sp489.

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Granitoids form the bulk of the Archean continental crust and preserve key information on early Earth evolution. India hosts five main Archean cratonic blocks (Aravalli, Bundelkhand, Singhbhum, Bastar and Dharwar). This book summarizes the available information on Archean granitoids of Indian cratons. The chapters cover a broad spectrum of themes related to granitoid typology, emplacement mechanism, petrogenesis, phase-equilibria modelling, temporal distribution, tectonic setting, and their roles in fluid evolution, metal delivery and mineralizations. The book presents a broader picture incorporating regional- to cratons-scale comparisons, implications for Archean geodynamic processes, and temporal changes thereof. This synthesis work, integrating modern concepts on granite petrology and crustal evolution, offers an irreplaceable body of reference information for any geologist interested in Archean Indian granitoids.

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DeLong, Edward F., Lance Trent Taylor, Terence L. Marsh et Christina M. Preston. « Visualization and Enumeration of Marine Planktonic Archaea and Bacteria by Using Polyribonucleotide Probes and Fluorescent In Situ Hybridization ». Applied and Environmental Microbiology 65, n^o 12 (1 décembre 1999) : 5554–63. http://dx.doi.org/10.1128/aem.65.12.5554-5563.1999.

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ABSTRACT Fluorescent in situ hybridization (FISH) using rRNA-specific oligonucleotide probes has emerged as a popular technique for identifying individual microbial cells. In natural samples, however, the signal derived from fluor-labeled oligonucleotide probes often is undetectable above background fluorescence in many cells. To circumvent this difficulty, we applied fluorochrome-labeled polyribonucleotide probes to identify and enumerate marine planktonic archaea and bacteria. The approach greatly enhanced the sensitivity and applicability of FISH with seawater samples, allowing confident identification and enumeration of planktonic cells to ocean depths of 3,400 m. Quantitative whole-cell hybridization experiments using these probes accounted for 90 to 100% of the total 4′,6-diamidino-2-phenylindole (DAPI)-stained cells in most samples. As predicted in a previous study (R. Massana, A. E. Murray, C. M. Preston, and E. F. DeLong, Appl. Environ. Microbiol. 63:50–56, 1997), group I and II marine archaea predominate in different zones in the water column, with maximal cell densities of 105/ml. The high cell densities of archaea, extending from surface waters to abyssal depths, suggest that they represent a large and significant fraction of the total picoplankton biomass in coastal ocean waters. The data also show that the vast majority of planktonic prokaryotes contain significant numbers of ribosomes, rendering them easily detectable with polyribonucleotide probes. These results imply that the majority of planktonic cells visualized by DAPI do not represent lysed cells or “ghosts,” as was suggested in a previous report.

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Ciscato, Emily R., Tomaso R. R. Bontognali, Simon W. Poulton et Derek Vance. « Copper and its Isotopes in Organic-Rich Sediments : From the Modern Peru Margin to Archean Shales ». Geosciences 9, n^o 8 (25 juillet 2019) : 325. http://dx.doi.org/10.3390/geosciences9080325.

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The cycling of copper (Cu) and its isotopes in the modern ocean is controlled by the interplay of biology, redox settings, and organic complexation. To help build a robust understanding of Cu cycling in the modern ocean and investigate the potential processes controlling its behavior in the geological past, this study presents Cu abundance and isotope data from modern Peru Margin sediments as well as from a suite of ancient, mostly organic-rich, shales. Analyses of an organic-pyrite fraction extracted from bulk modern sediments suggest that sulphidation is the main control on authigenic Cu enrichments in this setting. This organic-pyrite fraction contains, in most cases, >50% of the bulk Cu reservoir. This is in contrast to ancient samples, for which a hydrogen fluoride (HF)-dissolvable fraction dominates the total Cu reservoir. With <20% of Cu found in the organic-pyrite fraction of most ancient sediments, interpretation of the associated Cu isotope composition is challenging, as primary signatures may be masked by secondary processes. But the Cu isotope composition of the organic-pyrite fraction in ancient sediments hints at the potential importance of a significant Cu(I) reservoir in ancient seawater, perhaps suggesting that the ancient ocean was characterized by different redox conditions and a different Cu isotope composition to that of the modern ocean.

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Heard, Andy W., Nicolas Dauphas, Romain Guilbaud, Olivier J. Rouxel, Ian B. Butler, Nicole X. Nie et Andrey Bekker. « Triple iron isotope constraints on the role of ocean iron sinks in early atmospheric oxygenation ». Science 370, n^o 6515 (22 octobre 2020) : 446–49. http://dx.doi.org/10.1126/science.aaz8821.

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The role that iron played in the oxygenation of Earth’s surface is equivocal. Iron could have consumed molecular oxygen when Fe3+-oxyhydroxides formed in the oceans, or it could have promoted atmospheric oxidation by means of pyrite burial. Through high-precision iron isotopic measurements of Archean-Paleoproterozoic sediments and laboratory grown pyrites, we show that the triple iron isotopic composition of Neoarchean-Paleoproterozoic pyrites requires both extensive marine iron oxidation and sulfide-limited pyritization. Using an isotopic fractionation model informed by these data, we constrain the relative sizes of sedimentary Fe3+-oxyhydroxide and pyrite sinks for Neoarchean marine iron. We show that pyrite burial could have resulted in molecular oxygen export exceeding local Fe2+ oxidation sinks, thereby contributing to early episodes of transient oxygenation of Archean surface environments.

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de Wit, Maarten, et Christien Thiart. « Metallogenic fingerprints of Archaean cratons ». Geological Society, London, Special Publications 248, n^o 1 (2005) : 59–70. http://dx.doi.org/10.1144/gsl.sp.2005.248.01.03.

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Blättler, C. L., L. R. Kump, W. W. Fischer, G. Paris, J. J. Kasbohm et J. A. Higgins. « Constraints on ocean carbonate chemistry and pCO2 in the Archaean and Palaeoproterozoic ». Nature Geoscience 10, n^o 1 (28 novembre 2016) : 41–45. http://dx.doi.org/10.1038/ngeo2844.

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