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| Open AccessPelagic barite precipitation at micromolar ambient sulfate
The question of how significant barite deposits were able to form from early Earth’s low-sulfate seas remains controversial. Here, the authors show pelagic barite precipitation within a strongly barite-undersaturated ecosystem, highlighting the importance of particle-associated microenvironments.
- Tristan J. Horner
- , Helena V. Pryer
- & Richard D. Ricketts
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Article
| Open AccessMarine oxygen production and open water supported an active nitrogen cycle during the Marinoan Snowball Earth
Snowball Earth glaciations were some of the most extreme climate events in Earth history, and are temporally linked to major biogeochemical changes. Here, using geochemical proxies, the authors show that during the Marinoan glaciation, there was likely open water, active oxygen production, and nitrogen cycling.
- Benjamin W. Johnson
- , Simon W. Poulton
- & Colin Goldblatt
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Article
| Open AccessContribution of livestock H2S to total sulfur emissions in a region with intensive animal production
Hydrogen sulfide (H2S) from agricultural sources is generally omitted from sulfur emission estimates despite its abundance in livestock emissions. Here, the authors show that agriculture is the most important source of sulfur in Denmark using proton-transfer-reaction mass spectrometry measurements of H2S.
- Anders Feilberg
- , Michael Jørgen Hansen
- & Tavs Nyord
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Article
| Open AccessOxic-anoxic regime shifts mediated by feedbacks between biogeochemical processes and microbial community dynamics
The role of microbial communities in regime shifts is poorly understood. Here, the authors use a mathematical model and field data from a seasonally stratified lake to show that gradual environmental changes can induce oxic-anoxic regime shifts mediated by microbial community dynamics and redox processes.
- Timothy Bush
- , Muhe Diao
- & Jef Huisman
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Article
| Open AccessBiogenic manganese oxide nanoparticle formation by a multimeric multicopper oxidase Mnx
Significant challenges exist for structural characterization of enzymes responsible for biomineralization. Here the authors show that native mass spectrometry and high resolution electron microscopy can define the subunit topology and copper binding of a manganese oxidizing complex, and describe early stage formation of its mineral products
- Christine A. Romano
- , Mowei Zhou
- & Bradley M. Tebo
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Article
| Open AccessLate Neoproterozoic seawater oxygenation by siliceous sponges
The Ediacaran–Cambrian oxygenation of seawater is thought to have been caused by lifeforms engaging in ecosystem engineering. Here, the authors show that siliceous sponges increased seawater dissolved oxygen concentrations by redistributing organic carbon oxidation through filtering suspended organic matter.
- Michael Tatzel
- , Friedhelm von Blanckenburg
- & Dorothee Hippler
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Article
| Open AccessThe onset of widespread marine red beds and the evolution of ferruginous oceans
The evolution of oceanic redox state in the past is poorly known. Here, the authors present a temporal record of banded iron formations and marine red beds, which indicate deep-ocean oxygenation occurred in the middle Ediacaran, coinciding with the onset of widespread marine red beds.
- Haijun Song
- , Ganqing Jiang
- & Chengshan Wang
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Article
| Open AccessMajor agricultural changes required to mitigate phosphorus losses under climate change
The impact of climate change on phosphorus (P) loss from land to water is unclear. Here, the authors use P flux data, climate simulations and P transfer models to show that only large scale agricultural change will limit the effect of climate change on average winter P loads in three catchments across the UK.
- M. C. Ockenden
- , M. J. Hollaway
- & P. M. Haygarth
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Article
| Open AccessThe influence of Antarctic subglacial volcanism on the global iron cycle during the Last Glacial Maximum
Contributions of iron sources to Southern Ocean CO2sequestration during the last glacial period remain uncertain. Here, based on the biogeochemical analysis of subglacial calcites, the authors propose Antarctic volcanism, via subglacial drainage of Fe-rich waters, as a key contributor.
- Silvia Frisia
- , Laura S. Weyrich
- & Alan Cooper
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Article
| Open AccessAnthropogenic climate change has altered primary productivity in Lake Superior
The impacts of climate change on the Great Lakes’ ecosystems compared to historical records are unclear. Here, using paleolimnological evidence, the authors show that Lake Superior experienced a slow increase in productivity throughout the Holocene, but that this rate has increased in the last century.
- M. D. O’Beirne
- , J. P. Werne
- & E. D. Reavie
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Article
| Open AccessAstronomical pacing of the global silica cycle recorded in Mesozoic bedded cherts
While the global silica cycle is known to play an important role in long-term climate change, the driving factors remain unknown. Here, the authors present a ∼70 million year long record of early Mesozoic biogenic silica and propose orbitally-paced chemical weathering as a primary driver.
- Masayuki Ikeda
- , Ryuji Tada
- & Kazumi Ozaki
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| Open AccessEvidence for fungal and chemodenitrification based N2O flux from nitrogen impacted coastal sediments
Predicting nitrous oxide emissions (N2O) remains difficult due to the numerous N2O production pathways. Here, the authors use incubations simulating high nitrate inputs to show that, in intertidal sediments, increases in N2O flux are largely mediated by fungal denitrification and/or chemodenitrification.
- Scott D. Wankel
- , Wiebke Ziebis
- & Karsten Zengler
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Article
| Open AccessBiogenic non-crystalline U(IV) revealed as major component in uranium ore deposits
Crystalline uraninite is believed to be the dominant form in uranium deposits. Here, the authors find that non-crystalline U(IV) generated through biologically mediated U(VI) reduction is the predominant U(IV)species in ore deposits, implying that biogenic processes are more important than previously thought.
- Amrita Bhattacharyya
- , Kate M. Campbell
- & Thomas Borch
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| Open AccessMulticentennial record of Labrador Sea primary productivity and sea-ice variability archived in coralline algal barium
Continued warming and melting of Arctic sea-ice have led to increases in Labrador Sea phytoplankton productivity in recent decades. Here, the authors utilize a novel annually resolved palaeoproxy and propose that the recently observed increase in surface ocean productivity is unmatched since the Little Ice Age.
- P. Chan
- , J. Halfar
- & A. Hou
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Article
| Open AccessIron limitation of microbial phosphorus acquisition in the tropical North Atlantic
The influence iron exerts over the acquisition of dissolved organic phosphorus in regions of the oceans co-limited by nitrogen and phosphorus is poorly constrained. Here, the authors demonstrate enhanced alkaline phosphatase activity of natural marine microbial communities following iron fertilization.
- T. J. Browning
- , E. P. Achterberg
- & C. M. Moore
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Article
| Open AccessDust outpaces bedrock in nutrient supply to montane forest ecosystems
Dust is an important nutrient source to landscapes, but often the source of dust is poorly constrained. Here, the authors quantify the origin of different dust sources in the Sierra Nevada by analysing dust composition and suggest exogenic dust may drive nutrient budgets in montane ecosystems.
- S. M. Aciego
- , C. S. Riebe
- & E. L. Aronson
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Article
| Open AccessIron minerals within specific microfossil morphospecies of the 1.88 Ga Gunflint Formation
Fossil microorganisms older than 1.7 billion years are challenging to interpret due to their size, simple shapes, and alteration. Here, in 1.88 billion year old microfossils, the authors show a pattern of cellular preservation and internal iron nanominerals consistent with oxygenic photosynthetic bacteria.
- Kevin Lepot
- , Ahmed Addad
- & Emmanuelle J. Javaux
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Article
| Open AccessTemporal controls on silicic acid utilisation along the West Antarctic Peninsula
Sea-ice plays a key role in regulating nutrient dynamics and primary productivity along the Antarctica Peninsula margin. Here, the authors show that over the last 13 kyr nutrient dynamics have also been regulated by glacial discharge, highlighting the potential for future changes as glaciers continue to melt.
- George E. A. Swann
- , Jennifer Pike
- & Andrea M. Snelling
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| Open AccessSponge-associated bacteria mineralize arsenic and barium on intracellular vesicles
The marine spongeTheonella swinhoeiaccumulates toxic arsenic and barium. Here the authors show that these toxic elements are actually accumulated and mineralized within vesicles inside bacteria that live within the sponge tissues.
- Ray Keren
- , Boaz Mayzel
- & Micha Ilan
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| Open AccessClimatically sensitive transfer of iron to maritime Antarctic ecosystems by surface runoff
Glacially-derived iron fertilizes the Southern Ocean ecosystem, but the quantities transported by runoff from Antarctica are unknown. Here, the authors show significant fluxes associated with surface meltwater runoff, and demonstrate that a marked increase in export can be expected in response to climate warming.
- Andy Hodson
- , Aga Nowak
- & Gonçalo Vieira
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Article
| Open AccessMolecular composition of organic matter controls methylmercury formation in boreal lakes
Neurotoxic methylmercury can be found in high levels in aquatic systems, but the role of organic matter in methylmercury formation is not well understood. Here, Bravoet al. show that plankton-derived organic compounds enhance formation rates in boreal lakes.
- Andrea G. Bravo
- , Sylvain Bouchet
- & Stefan Bertilsson
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| Open AccessAtmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon
It is unclear why atmospheric O2 remained at low levels for >1.5 billion years following the Great Oxidation Event. Here, the authors show that tectonic recycling of previously accumulated sedimentary organic carbon, and oxygen sensitivity of its oxidative weathering stabilized O2at ∼1–10% of present levels.
- Stuart J. Daines
- , Benjamin J. W. Mills
- & Timothy M. Lenton
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Article
| Open AccessIce sheets as a missing source of silica to the polar oceans
Glacial runoff often has relatively low dissolved silica concentrations and therefore ice sheets have been thought insignificant in the global silicon cycle. Here, the authors show that ice sheets likely play an important role in the production and export of dissolved and dissolvable amorphous silica downstream.
- Jon R. Hawkings
- , Jemma L. Wadham
- & Rob Raiswell
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| Open AccessNitrous oxide as a function of oxygen and archaeal gene abundance in the North Pacific
Understanding the production processes behind oceanic sources of nitrous oxide (N2O), a potent greenhouse gas, is of critical importance. Here, the authors reveal an archaeal-mediated N2O production pathway in the North Pacific, which increases exponentially with decreasing oxygen.
- Mark Trimmer
- , Panagiota-Myrsini Chronopoulou
- & Kevin J. Purdy
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Article
| Open AccessSulfur mass-independent fractionation in subsurface fracture waters indicates a long-standing sulfur cycle in Precambrian rocks
Precambrian rocks host a deep hydrosphere, but where dissolved sulfate, crucial for microbial life, comes from is unclear. At 2.4 km depth in the Canadian shield, Li et al. find that oxidation of sulfides in the host rocks creates sulfate thus providing a long-term mechanism for the deep biosphere sulfate.
- L. Li
- , B. A. Wing
- & B. Sherwood Lollar
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| Open AccessBiotic and abiotic controls on co-occurring nitrogen cycling processes in shallow Arctic shelf sediments
Arctic continental shelves could store a significant amount of nitrogen, yet the specific nitrogen transformation pathways in these sediments remain unknown. Using nitrogen tracers, McTigueet al. simultaneously measure multiple pathways in the Chukchi Sea, confirming the Arctic as a major nitrogen sink.
- N. D. McTigue
- , W. S. Gardner
- & A. K. Hardison
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| Open AccessThousands of microbial genomes shed light on interconnected biogeochemical processes in an aquifer system
Microorganisms from the terrestrial subsurface are understudied. Here, Anantharamanet al. analyse aquifer sediments and groundwater by genome-resolved metagenomics and reconstruct 2,540 genomes representing the majority of known bacterial phyla as well as 47 new phylum-level lineages.
- Karthik Anantharaman
- , Christopher T. Brown
- & Jillian F. Banfield
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| Open AccessReturn of naturally sourced Pb to Atlantic surface waters
Anthropogenic lead (Pb) has overwhelmed natural Pb sources for over a century, yet the phasing out of leaded petrol in the early 2000s has renewed hope. Here, Bridgestock et al. use Pd isotopes to reassess the origins of Pd deposited in the tropical North Atlantic and reveal a significant natural source.
- Luke Bridgestock
- , Tina van de Flierdt
- & Hein J. W. de Baar
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| Open AccessSelf-assembly of biomorphic carbon/sulfur microstructures in sulfidic environments
Organic materials mineralized with sulfur are considered to be a product of biological activity in natural environments and the fossil record. Here, Cosmidis and Templeton show that sulfide can abiotically drive the self-assembly of organic carbon microstructures mineralized with elemental sulfur.
- Julie Cosmidis
- & Alexis S. Templeton