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| Open AccessDistinct iron isotopic signatures and supply from marine sediment dissolution
The dissolution of iron from sediments along ocean margins may stimulate photosynthesis and moderate global climate. This study shows how margin sediments supply iron in varying amounts between regions, and by distinct mechanisms, which may be due to geological characteristics and hydrological controls on land.
- William B. Homoky
- , Seth G. John
- & Rachel A. Mills
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Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation
Debates on the formation of banded iron formations (BIFs) in ancient iron-rich oceans are dominated by contradictions between biological and non-biological iron cycling. This study provides environmental evidence that directly implicates photosynthetic iron-oxidizing microorganisms in vast-scale BIF deposition.
- Ernest Chi Fru
- , Magnus Ivarsson
- & Marco Stampanoni
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| Open AccessCarbon dioxide concentration dictates alternative methanogenic pathways in oil reservoirs
Deep subsurface formations are potential sites for carbon capture and storage but how subsurface microbial communities may respond to this is not clear. Here, Mayumi et al. construct microcosms and show that increasing CO2partial pressure via carbon capture and storage more than doubles the rate of methanogenesis.
- Daisuke Mayumi
- , Jan Dolfing
- & Yoichi Kamagata
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Role of biogenic silica in the removal of iron from the Antarctic seas
Iron plays a key role in controlling biological production in the Southern Ocean, yet mechanisms regulating iron availability are not completely understood. Here, Ingall et al.show that structural incorporation of reduced, organic iron into biogenic silica represents a new and substantial removal pathway.
- Ellery D. Ingall
- , Julia M. Diaz
- & Jay A. Brandes
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Another rapid event in the carbon-14 content of tree rings
A strong increase in atmospheric 14C was measured in tree rings at AD 774 to 775, providing potential evidence of large cosmic ray fluxes to Earth, but the cause of this event is unclear. Here, Miyake et al. report a second 14C event in AD 993, which suggests that the most likely cause was a large solar proton event.
- Fusa Miyake
- , Kimiaki Masuda
- & Toshio Nakamura
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Biological carbon precursor to diagenetic siderite with spherical structures in iron formations
The role of bacteria in the origin of iron formations (IF) remains unclear because no direct evidence for their involvement exists. This study shows that spherical siderite in deep-water IF represents a biosignature for photoferrotrophy, whereas massive siderite reflects high cyanobacterial biomass in shallow-water.
- Inga Köhler
- , Kurt O Konhauser
- & Andreas Kappler
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Reconciliation of marine and terrestrial carbon isotope excursions based on changing atmospheric CO2 levels
Carbon isotope excursions (CIEs) measured in marine and terrestrial substrates indicate large-scale changes in the global carbon cycle. Schubert and Jahren show that larger-amplitude CIEs measured in terrestrial substrates reflect increased carbon isotope fractionation by land plants under elevated atmospheric CO2.
- Brian A. Schubert
- & A. Hope Jahren
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A novel metatranscriptomic approach to identify gene expression dynamics during extracellular electron transfer
Extracellular electron transfer is a ubiquitous process that occurs in natural microbial communities. Here, Ishii et al.identify specific microbial strains and genes involved in extracellular electron transfer in a biofilm community that is associated with a microbial fuel cell.
- Shun’ichi Ishii
- , Shino Suzuki
- & Orianna Bretschger
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Nitrogen cycle feedbacks as a control on euxinia in the mid-Proterozoic ocean
Clear evidence between sulphidic conditions and denitrification in the Proterozoic ocean should be observable in the rock record. Here, minimalistic biogeochemical modelling shows how periods of extensive sulphate reduction must have gone hand-in-hand with low denitrification and available nitrate.
- R.A. Boyle
- , J.R. Clark
- & T.M. Lenton
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Mechanisms of carbon storage in mountainous headwater rivers
Rivers receive more terrestrial carbon than they transport to the ocean, leaving carbon stored along the way. Here, with an estimate of carbon storage in the headwater rivers of the Rocky Mountains, the authors show that broad valley bottoms with old-growth forest store most of the above- and below-ground carbon.
- Ellen Wohl
- , Kathleen Dwire
- & Roberto Bazan
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Warming and nitrogen deposition lessen microbial residue contribution to soil carbon pool
Microbes appear to play an important role in carbon sequestration. Here, the composition of microbial residues in a California grassland with elevated carbon dioxide, warming and nitrogen deposition reveals that warming and nitrogen deposition can both alter the fraction of carbon derived from microbes in soils.
- Chao Liang
- & Teri C. Balser
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Atmospheric phosphorus deposition may cause lakes to revert from phosphorus limitation back to nitrogen limitation
Increased atmospheric input of nitrogen has shifted planktonic lake nutrient systems from natural nitrogen to human-induced phosphorus limitation. This study proposes that decades of increased atmospheric phosphorus in the Pyrenean lake district may have reverted the system from phosphorus back to nitrogen-limited.
- L. Camarero
- & J. Catalan
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Evidence for methane production by saprotrophic fungi
Methane is an important anthropogenic greenhouse gas and is thought to be produced by industrial processes and prokaryotic methanogenic Archaea. In this study, the saprotrophic fungi,Basidiomycetes, is shown to produce methane in the absence of methanogenic Archaea.
- Katharina Lenhart
- , Michael Bunge
- & Frank Keppler
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| Open AccessPronounced interannual variability in tropical South Pacific temperatures during Heinrich Stadial 1
During the last glacial termination, the North Atlantic experienced a cold interval, but its impact on tropical climate variability is not clear. Here, a fossil Tahiti coral record shows that tropical sea surface temperature varied actively during this event, consistent with climate model simulations.
- Thomas Felis
- , Ute Merkel
- & Miriam Pfeiffer
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The oceanic biological pump modulates the atmospheric transport of persistent organic pollutants to the Arctic
Persistent organic pollutants can reach and pollute pristine environments, such as the Arctic Ocean, through atmospheric transport. This study shows that the oceanic biological pump can sequester atmospheric polychlorinated biphenyls, reducing the transport of pollutants to the Arctic Ocean.
- Cristóbal Galbán-Malagón
- , Naiara Berrojalbiz
- & Jordi Dachs
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Past daily light cycle recorded in the strontium/calcium ratios of giant clam shells
A record of the daily light cycle in tropical regions is difficult to extract from biogenic marine carbonates such as shells. Here, the precise analysis of Sr/Ca ratios is shown in a cultivated giant clam shell, revealing variations that reflect the daily light cycle and the potential for future development of a proxy.
- Yuji Sano
- , Sayumi Kobayashi
- & Kenji Iwai
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Experimental drying intensifies burning and carbon losses in a northern peatland
Peatlands are a sink for atmospheric carbon dioxide and make up a large soil carbon reservoir. Here, studies of the interaction between drainage and fire show that long-term carbon emissions will likely exceed rates of carbon uptake, reducing the northern peatland carbon sink.
- M.R. Turetsky
- , W.F. Donahue
- & B.W. Benscoter
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Osmium evidence for synchronicity between a rise in atmospheric oxygen and Palaeoproterozoic deglaciation
The Early Palaeoproterozoic saw glaciations and a rise in atmospheric oxygen, but the link between these two changes is poorly understood. Here, osmium isotope records from sedimentary rocks indicate synchronicity between an episode of increasing oxygen and a glacial transition.
- Yasuhito Sekine
- , Katsuhiko Suzuki
- & Teruyuki Maruoka
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| Open AccessDust inputs and bacteria influence dissolved organic matter in clear alpine lakes
Dissolved organic matter, the main form of aquatic organic carbon, supports the aquatic food web and regulates light penetration in lakes. This study probes the main influences on the optical properties of dissolved organic matter in a global dataset of alpine and remote lakes revealing latitudinal trends.
- N. Mladenov
- , R. Sommaruga
- & I. Reche
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Global-scale latitudinal patterns of plant fine-root nitrogen and phosphorus
Through fine-root nutrient chemistry, it is possible to study ecosystem-scale biogeochemical cycling. Compiling data from 211 studies measuring nitrogen and phosphorus in plant roots, Yuanet al. find that tropical ecosystems are more phosphorous-limited than higher latitudes.
- Z.Y. Yuan
- , Han Y.H. Chen
- & Peter B. Reich
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| Open AccessMultiple S-isotopic evidence for episodic shoaling of anoxic water during Late Permian mass extinction
A final catastrophe killed 90% of marine species at the end of the Permian period, but significant biodiversity loss preceded this event. In this study, sulphur isotope evidence suggests that incursion of anoxic water into shallow regions may have contributed to biodiversity loss.
- Yanan Shen
- , James Farquhar
- & Boswell A. Wing
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Historical land use change has lowered terrestrial silica mobilization
Continental export of silicon to the coast is linked to ocean carbon sinks, but terrestrial silicon fluxes have not been quantified. Here, human deforestation and cultivation of the landscape are shown to be the most important factors in silicon mobilization in temperate European watersheds.
- Eric Struyf
- , Adriaan Smis
- & Patrick Meire
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| Open AccessDiscovery of a black smoker vent field and vent fauna at the Arctic Mid-Ocean Ridge
The Arctic Mid-Ocean Ridge spreads extremely slowly and hydrothermal vent fields have not been reported in its vicinity. Pedersenet al. describe a black smoker vent field with large hydrothermal deposits and novel fauna distinct from those found in similar environments in the Atlantic.
- Rolf B. Pedersen
- , Hans Tore Rapp
- & Steffen L. Jorgensen
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Crustaceans from bitumen clast in Carboniferous glacial diamictite extend fossil record of copepods
Copepod crustaceans are extremely abundant but fossilize poorly given their fragility; the earliest known fossils are from the Cretaceous period. Selden and colleagues report copepod fossils dating from the Carboniferous in a bitumen clast in Oman, extending their fossil record by 188 million years.
- Paul A. Selden
- , Rony Huys
- & Paul N. Taylor
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| Open AccessSustainable biochar to mitigate global climate change
The storage in soils of biochar, the product of biomass pyrolysis, has been proposed as an attractive option to mitigate climate change. Amonette and co-workers model the potential impact of biochar and find that it could eliminate more carbon from the atmosphere than using the same biomass for biofuel.
- Dominic Woolf
- , James E. Amonette
- & Stephen Joseph
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Biogeography and habitat modelling of high-alpine bacteria
The spatial distribution and parameters that affect soil microorganism communities are largely unknown. In this study, bacterial communities up to 240 metres apart are shown to be similar and are affected by soil pH, plant abundance and snow depth.
- Andrew J. King
- , Kristen R. Freeman
- & Steven K. Schmidt