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| Open AccessGroundwater discharge impacts marine isotope budgets of Li, Mg, Ca, Sr, and Ba
Groundwater discharge is a mechanism that transports chemicals from inland systems to the ocean, but it has been considered of secondary influence compared to rivers. Here the authors assess the global significance of groundwater discharge, finding that it has a unique and important contribution to ocean chemistry and Earth-system models.
- Kimberley K. Mayfield
- , Anton Eisenhauer
- & Adina Paytan
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Article
| Open AccessAround one third of current Arctic Ocean primary production sustained by rivers and coastal erosion
The Arctic Ocean is influenced by carbon and nutrients from rivers and erosion, but how this affects phytoplankton productivity is not understood. Here, the authors use a spatio-temporally resolved biogeochemical model to estimate that the input of carbon and nutrients fuels 28–51% of annual Arctic Ocean productivity.
- Jens Terhaar
- , Ronny Lauerwald
- & Laurent Bopp
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Article
| Open AccessA new hypothesis for the origin of Amazonian Dark Earths
Amazonian Dark Earth is soil that has had mysteriously high fertility since ancient times, despite the fact that surrounding soils have very low nutrients. Here the authors’ use of isotope reconstructions indicate that these soils predate human settlement and could have alluvial and burning origins.
- Lucas C. R. Silva
- , Rodrigo Studart Corrêa
- & Roberto Ventura Santos
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Article
| Open AccessIron mineral dissolution releases iron and associated organic carbon during permafrost thaw
Iron minerals trap carbon in permafrost, preventing microbial degradation and release to the atmosphere as CO2, but the stability of this carbon as permafrost thaws is unclear. Here the authors use nanoscale analyses to show that thaw conditions stimulate Fe-reducing bacteria that trigger carbon release.
- Monique S. Patzner
- , Carsten W. Mueller
- & Casey Bryce
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Article
| Open AccessStrong hydroclimatic controls on vulnerability to subsurface nitrate contamination across Europe
Excess fertilizer use causes subsurface contamination. Here, the authors conduct an assessment of water quality vulnerability across Europe, finding that 75% of agricultural regions are susceptible to nitrate contamination for least one-third of the year, two times more than using standard estimation procedure.
- R. Kumar
- , F. Heße
- & S. Attinger
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Article
| Open AccessSerpentine alteration as source of high dissolved silicon and elevated δ30Si values to the marine Si cycle
The Si cycle is important to ocean productivity and nutrient cycling, however there are uncertainties in global budgets. Here the authors use a multi-isotope approach on seafloor sediments and pore fluids, finding that an unappreciated source of Si to the ocean is the degradation of seafloor serpentinites.
- Sonja Geilert
- , Patricia Grasse
- & Catriona D. Menzies
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Article
| Open AccessBacteria are important dimethylsulfoniopropionate producers in marine aphotic and high-pressure environments
Dimethylsulfoniopropionate (DMSP) is an osmolyte produced by marine microbes that plays an important role in nutrient cycling and atmospheric chemistry. Here the authors go to the Mariana Trench—the deepest point in the ocean—and find bacteria are key DMSP producers, and that DMSP has a role in protection against high pressure.
- Yanfen Zheng
- , Jinyan Wang
- & Xiao-Hua Zhang
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Article
| Open AccessSubstrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming
Microbial ammonia oxidation is important in marine nutrient cycling and greenhouse gas dynamics, but the responses to ocean warming are unclear. Here coast to open ocean incubations show that projected year 2100 temperatures might be too hot for these microbes in oligotrophic regions to handle, but may facilitate oxidation rates in coastal waters.
- Zhen-Zhen Zheng
- , Li-Wei Zheng
- & Shuh-Ji Kao
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Article
| Open AccessMethylmercury produced in upper oceans accumulates in deep Mariana Trench fauna
Monomethylmercury is a toxin that humans can be exposed to after consumption of seafood in which it has bioaccumulated. Here the authors show that amphipods in the deepest point of the global ocean contain monomethylmercury with surface origins, suggesting rapid sinking of this toxin on particles.
- Ruoyu Sun
- , Jingjing Yuan
- & Congqiang Liu
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Article
| Open AccessProgressive nitrogen limitation across the Tibetan alpine permafrost region
Massive stores of carbon and nutrients in permafrost could be released by global warming. Here the authors show that though warming across the Tibetan alpine permafrost region accelerates nitrogen liberation, contrary to expectations the elevated nutrients do not alleviate plant nitrogen limitation.
- Dan Kou
- , Guibiao Yang
- & Yuanhe Yang
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Article
| Open AccessRemote assessment of the fate of phytoplankton in the Southern Ocean sea-ice zone
Satellites can observe marine phytoplankton, but observations are sparse in seasonally dark, cloudy environments like the Southern Ocean. These authors use Argo floats to track the fate of phytoplankton blooms off Antarctica and determine 10% of biomass is exported, while 90% is prey to grazing.
- Sébastien Moreau
- , Philip W. Boyd
- & Peter G. Strutton
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Article
| Open AccessPermo–Triassic boundary carbon and mercury cycling linked to terrestrial ecosystem collapse
The environmental changes at the Permian–Triassic boundary are thought to have been caused primarily by volcanic eruptions. Here the authors develop a model to show that the loss of ecosystems on land and consequent massive terrestrial biomass oxidation triggered large biogeochemical changes in the oceans at the time of the marine mass extinction.
- Jacopo Dal Corso
- , Benjamin J. W. Mills
- & Paul B. Wignall
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Article
| Open AccessMantle data imply a decline of oxidizable volcanic gases could have triggered the Great Oxidation
The early Earth’s atmosphere had very low oxygen levels for hundreds of millions of years, until the 2.4 Ga Great Oxidation Event, which remains poorly understood. Here, the authors show that reducing Archean volcanic gases could have prevented atmospheric O2 from accumulating, and therefore mantle oxidation was likely very important in setting the evolution of O2 and aerobic life.
- Shintaro Kadoya
- , David C. Catling
- & Ariel D. Anbar
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Article
| Open AccessCo-evolution of primitive methane-cycling ecosystems and early Earth’s atmosphere and climate
Biology can profoundly influence the planet’s climate, but over Earth’s long history these effects are poorly constrained. Here the authors show that on early Earth, the evolution of microbes producing and consuming methane likely controlled warming and glacial events, and thus Earth’s habitability
- Boris Sauterey
- , Benjamin Charnay
- & Régis Ferrière
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Article
| Open AccessMicroplastics affect sedimentary microbial communities and nitrogen cycling
Plastic pollution has infiltrated every ecosystem, but few studies have quantified the biogeochemical or ecological effects of plastic. Here the authors show that microplastics in ocean sediment can significantly alter microbial community structure and nitrogen cycling.
- Meredith E. Seeley
- , Bongkeun Song
- & Robert C. Hale
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Article
| Open AccessArsenic contamination of Bangladesh aquifers exacerbated by clay layers
Generally it is thought that confining clay layers provide protection to low-arsenic groundwaters against intrusion of shallower, high-arsenic groundwater bodies. Here, the authors show that impermeable clay layers can increase arsenic input to underlying groundwater systems due to reduction of iron oxides coupled to carbon oxidation.
- Ivan Mihajlov
- , M. Rajib H. Mozumder
- & Alexander van Geen
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Article
| Open AccessIron-mediated organic matter decomposition in humid soils can counteract protection
Reactive iron minerals protect vast amounts of terrestrial carbon from decomposition and release as CO2. Here the authors show that reactive iron alone does not provide sufficient protection except under strict oxic conditions—instead, iron itself promotes carbon decomposition.
- Chunmei Chen
- , Steven J. Hall
- & Aaron Thompson
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Article
| Open AccessThe role of calcium in regulating marine phosphorus burial and atmospheric oxygenation
Previous work suggests that marine oxygen levels and bioturbation are important factors that shape phosphorus burial and the size of the marine biosphere. Here the authors show that seawater calcium concentration is a key factor in controlling marine P burial, and thus the global oxygen cycle.
- Mingyu Zhao
- , Shuang Zhang
- & Noah Planavsky
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Article
| Open AccessExtracellular electron transfer-dependent anaerobic oxidation of ammonium by anammox bacteria
Bacteria capable of anaerobic ammonium oxidation (anammox) produce half of the nitrogen gas in the atmosphere, but much of their physiology is still unknown. Here the authors show that anammox bacteria are capable of a novel mechanism of ammonium oxidation using extracellular electron transfer.
- Dario R. Shaw
- , Muhammad Ali
- & Pascal E. Saikaly
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Article
| Open AccessPersistent global marine euxinia in the early Silurian
The Late Ordovician mass extinction has been attributed to extended marine anoxia. Here, the authors use a metal isotope mass balance model and find the marine anoxic event lasted over 3 million years, notably longer than the anoxic event associated with the Permian-Triassic extinction and Cretaceous ocean anoxic events.
- Richard G. Stockey
- , Devon B. Cole
- & Erik A. Sperling
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Article
| Open AccessDrought alters the biogeochemistry of boreal stream networks
High latitude droughts are increasing, but their effects on freshwater systems are poorly understood. Here the authors investigate Sweden’s most severe drought in the last century and show that these dry conditions induce hypoxia and elevated methane production from streams.
- Lluís Gómez-Gener
- , Anna Lupon
- & Ryan A. Sponseller
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Article
| Open AccessAnomalous fractionation of mercury isotopes in the Late Archean atmosphere
Earth’s surface underwent a dramatic transition ~2.3 billion years ago when atmospheric oxygen first accumulated during the Great Oxidation Event. Here, the authors find that biogenic methane and volcanic emissions played a vital role in the reduced Late Archean atmosphere.
- Aubrey L. Zerkle
- , Runsheng Yin
- & Stephen E. Grasby
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Article
| Open AccessMapping anthropogenic mineral generation in China and its implications for a circular economy
While a large quantity of underground mineral resources can be converted into manufactured products, a majority is still solid waste disposal. Here the authors found a large increase in total weight of anthropogenic mineral from 2010 to 2050 with faster growth rate for precious metals.
- Xianlai Zeng
- , Saleem H. Ali
- & Jinhui Li
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Article
| Open AccessCoral skeletons reveal the history of nitrogen cycling in the coastal Great Barrier Reef
Coastal pollution degrades ecosystems, but long term impacts are unknown in Australia’s Great Barrier Reef. Using a 333 year record of coral skeleton nitrogen isotopes, Erler and colleagues show that increasing nutrient inputs since European settlement have led to unexpected feedback responses.
- Dirk V. Erler
- , Hanieh Tohidi Farid
- & Janice M. Lough
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Article
| Open AccessFresh groundwater discharge insignificant for the world’s oceans but important for coastal ecosystems
The authors here present the global entry of nutrients into marine systems through fresh submarine groundwater discharge to be below 1%. However, they also identify hotspots and argue that about 25% of world’s estuaries are at danger of eutrophication.
- Elco Luijendijk
- , Tom Gleeson
- & Nils Moosdorf
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| Open AccessAggravation of reactive nitrogen flow driven by human production and consumption in Guangzhou City China
There lacks research to figure out the variations in sources, magnitude, and spatiotemporal patterns of Nr flows in urban system. Here the authors develop a coupled human-natural urban nitrogen flow analysis model and show that anthropogenic perturbations not only intensify Nr input to sustain increasing demands for production and consumption of cities, but also greatly change the Nr distribution pattern in the urban system.
- Yue Dong
- , Linyu Xu
- & Lei Chen
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Article
| Open AccessMeasured greenhouse gas budgets challenge emission savings from palm-oil biodiesel
Palm oil biofuels are touted as a sustainable alternative to fossil fuels. Meijide and colleagues use greenhouse gas measurements to update life cycle assessments of oil palm growth scenarios and show that despite the promise, emission savings do not meet sustainability standards.
- Ana Meijide
- , Cristina de la Rua
- & Alexander Knohl
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Article
| Open AccessDistinct iron cycling in a Southern Ocean eddy
Eddies are common ocean features that isolate large swaths of seawater, but it is unclear how they influence productivity of phytoplankton trapped inside. Here Ellwood and colleagues use stable and radiogenic isotopes to characterize a Southern Ocean eddy, finding vanishingly low iron concentrations that drive low productivity across the region.
- Michael J. Ellwood
- , Robert F. Strzepek
- & Philip W. Boyd
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Article
| Open AccessUnprecedented Fe delivery from the Congo River margin to the South Atlantic Gyre
The influence of the Congo River margin on surface Fe concentrations is understudied. Here the authors show that such influence is evident over 1000 km from the Congo outflow.
- Lúcia H. Vieira
- , Stephan Krisch
- & Eric P. Achterberg
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Article
| Open AccessThe shift of phosphorus transfers in global fisheries and aquaculture
Despite growing aquaculture production and environmental concerns on phosphorus (P) enrichment, the P budgets of fisheries have been largely overlooked. Here, Huang et al. calculate global fishery P budgets and estimate P use efficiency for a wide range of aquaculture systems.
- Yuanyuan Huang
- , Phillipe Ciais
- & Haicheng Zhang
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Article
| Open AccessMicrobial Fe(III) reduction as a potential iron source from Holocene sediments beneath Larsen Ice Shelf
Recent recession of the Larsen Ice Shelf C has revealed that microbial alteration of illite can occur within marine sediments, a process previously thought to only occur abiotically during low-grade metamorphism. Here, the authors show that such microbial alteration of illite could provide a potential source of Fe release to Southern Ocean waters during Holocene glacial cycles.
- Jaewoo Jung
- , Kyu-Cheul Yoo
- & Jinwook Kim
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Article
| Open AccessNew isotope constraints on the Mg oceanic budget point to cryptic modern dolomite formation
Earth’s carbon cycle and oceanic magnesium cycle are controlled by processes such as weathering, volcanism and precipitation of carbonates, such as dolomite. Here, the authors contradict the view that modern dolomite formation is rare and suggest instead that dolomite accounts for ~40–60% of the global oceanic Mg output in the last 20 Ma.
- Netta Shalev
- , Tomaso R. R. Bontognali
- & Derek Vance
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Article
| Open AccessTropical carbon sink accelerated by symbiotic dinitrogen fixation
The contribution of symbiotic dinitrogen fixation to the forest carbon sink could change throughout forest succession. Here the authors model nitrogen cycling and light competition between trees based on data from Panamanian forest plots, showing that fixation contributes substantially to the carbon sink in early successional stages.
- Jennifer H. Levy-Varon
- , Sarah A. Batterman
- & Lars O. Hedin
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Article
| Open AccessMinimal biomass deposition in banded iron formations inferred from organic matter and clay relationships
Banded iron formations could have formed in the early oceans due to microbial metabolism. Here Dodd and colleagues find little organic carbon in these formations, indicating microbial iron cycling was minimal and could have limited the recycling of important nutrients to overlying waters.
- Matthew S. Dodd
- , Dominic Papineau
- & Juha A. Karhu
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Article
| Open AccessThe interplay between regeneration and scavenging fluxes drives ocean iron cycling
Iron is crucial for marine photosynthesis, but observational constraints on the magnitude of key iron cycle processes are lacking. Here the authors use a range of observational data sets to demonstrate that the balance between iron re-supply and removal in the subsurface controls upper ocean iron limitation.
- Alessandro Tagliabue
- , Andrew R. Bowie
- & Philip W. Boyd
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Article
| Open AccessSoil net nitrogen mineralisation across global grasslands
Nitrogen mineralisation (Nmin), an important index of soil fertility, is often determined in the laboratory, with an uncertain relationship to Nmin under field conditions. Here the authors show that combining laboratory measurements with environmental data greatly improves predictions of field Nmin at a global scale.
- A. C. Risch
- , S. Zimmermann
- & B. Moser
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Article
| Open AccessConstraining the rise of oxygen with oxygen isotopes
The loss of anomalous sulfur isotope compositions from sedimentary rocks has been considered a symptom of permanent atmospheric oxygenation. Here the authors show sulfur and oxygen isotope evidence from < 2.31 Ga sedimentary barium sulphates (barites) from the Turee Creek Basin, W. Australia, demonstrating the influence of local non-atmospheric processes on anomalous sulfur isotope signals.
- B. A. Killingsworth
- , P. Sansjofre
- & S. V. Lalonde
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Article
| Open AccessLake sedimentary biogenic silica from diatoms constitutes a significant global sink for aluminium
Diatoms drive biogeochemical cycling of aluminum by incorporating this element into their shells, but this process has not been quantified in freshwater systems. Here the authors quantify diatom-mediated aluminum fluxes in lakes and determine that they rival the aluminum sink in the global ocean.
- Dong Liu
- , Peng Yuan
- & Wenxiao Fan
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Article
| Open AccessMarine nitrogen fixers mediate a low latitude pathway for atmospheric CO2 drawdown
Iron fertilisation of the high latitude oceans is a well-established biological mechanism to explain the ice age drawdown of atmospheric CO2, yet modelling has so far struggled to account for a sufficient drawdown via this mechanism. Here, the authors propose that N2 fixers, which inhabit the lower latitude ocean, made a significant contribution to CO2 drawdown and so amplified the global response to iron fertilisation during ice ages.
- Pearse J. Buchanan
- , Zanna Chase
- & Nathaniel L. Bindoff
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Article
| Open AccessOrganic sulfur was integral to the Archean sulfur cycle
Marine chemistry during the Early Earth (over 2.7 billion years ago) is commonly inferred to have been inorganically sulfate-reducing. Here, the authors argue that organic sulfur cycling may have played a previously unrecognized, yet important, role in the formation of ancient Archean marine sulfides.
- Mojtaba Fakhraee
- & Sergei Katsev
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Article
| Open AccessThe role of marine sediment diagenesis in the modern oceanic magnesium cycle
The oceanic magnesium cycle is closely linked to Earth’s carbon cycle and long-term climate change, due to processes such as continental weathering and authigenic mineral formation. Here, the authors update the global oceanic magnesium budget by quantifying the flux of magnesium from oceans to marine sediments and the associated isotopic fractionation.
- Richard D. Berg
- , Evan A. Solomon
- & Fang-Zhen Teng
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Article
| Open AccessSignificant contribution of metastable particulate organic matter to natural formation of silver nanoparticles in soils
Silver nanoparticles are known environmental contaminants, however it is unclear whether they arise in soils through natural processes, anthropogenic processes, or both. Here Huang and colleagues offer fresh insight into the natural formation of these contaminants by soil particulate organic matter exposed to solar irradiation.
- Ying-Nan Huang
- , Ting-Ting Qian
- & Dong-Mei Zhou
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Article
| Open AccessManganese and iron deficiency in Southern Ocean Phaeocystis antarctica populations revealed through taxon-specific protein indicators
Low manganese availability could be a major control of phytoplankton growth in the Southern Ocean. Here the authors identify proteomic signatures of low manganese and iron availability in phytoplankton cultures and detect those signatures in Antarctic field samples.
- Miao Wu
- , J. Scott P. McCain
- & Erin M. Bertrand
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Review Article
| Open AccessSubseafloor life and its biogeochemical impacts
Subseafloor microbial activities are central to global biogeochemical cycles, affecting Earth’s surface oxidation, ocean chemistry, and climate. Here the authors review present understanding of subseafloor microbes and their activities, identify research gaps, and recommend approaches to fill those gaps.
- Steven D’Hondt
- , Robert Pockalny
- & Arthur J. Spivack
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Article
| Open AccessAnoxygenic photosynthesis and the delayed oxygenation of Earth’s atmosphere
Competition dynamics between early Earth photosynthetic microorganisms are unclear. Here, the authors demonstrate that competition for light and nutrients between oxygenic phototrophs and Fe-based photosynthesizers in surface oceans provides a novel ecophysiological mechanism for the protracted oxygenation of Earth’s atmosphere.
- Kazumi Ozaki
- , Katharine J. Thompson
- & Christopher T. Reinhard
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Article
| Open AccessLoss of fixed nitrogen causes net oxygen gain in a warmer future ocean
Ocean anoxic events threaten marine ecosystems, and they are predicted to increase as the climate warms. Using model simulations, Oschlies and colleagues show that in spite of rising temperatures, after transitory deoxygenation, microbial denitrification could lead to oxygen increases that exceed preindustrial levels.
- Andreas Oschlies
- , Wolfgang Koeve
- & Paul Kähler
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Article
| Open AccessTracing and constraining anthropogenic aerosol iron fluxes to the North Atlantic Ocean using iron isotopes
The relative importance of crustal vs. anthropogenic dust deposition for iron cycling in the surface ocean is unclear. Based on analysis of iron isotope data from North Atlantic aerosol samples, the authors can reveal the relative importance of anthropogenic iron emissions and its impact on marine biogeochemistry.
- Tim M. Conway
- , Douglas S. Hamilton
- & Seth G. John
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Article
| Open AccessHydrothermal vents trigger massive phytoplankton blooms in the Southern Ocean
Hydrothermal activity is recognized to be significant in regulating the dynamics of trace elements in the ocean. Here the authors report the first observational evidence of upwelled hydrothermally influenced deep waters stimulating massive phytoplankton blooms in the Southern Ocean.
- Mathieu Ardyna
- , Léo Lacour
- & Hervé Claustre
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Article
| Open AccessEvidence for fungi and gold redox interaction under Earth surface conditions
The role of fungi in the biogeochemical cycling of gold remains unclear. Here the authors show that fungi can initiate gold oxidation under supergene conditions, thereby impacting gold mobilisation and secondary deposit formation in terrestrial environments.
- Tsing Bohu
- , Ravi Anand
- & Mike Verrall