Element cycles

  • Article
    | Open Access

    Nowhere is biomass burning more abundant than on the African continent, but the biogeochemical impacts on forests are poorly understood. Here the authors show that biomass burning leads to high phosphorus deposition in the Congo basin, which scales with forest age as a result of increasing canopy complexity.

    • Marijn Bauters
    • , Travis W. Drake
    •  & Pascal Boeckx
  • Article
    | Open Access

    N2 fixation was key to the expansion of life on Earth, but which organisms fixed N2 and if Mo-nitrogenase was functional in the low Mo early ocean is unknown. Here, the authors show that purple sulfur bacteria fix N2 using Mo-nitrogenase in a Proterozoic ocean analogue, despite low Mo conditions.

    • Miriam Philippi
    • , Katharina Kitzinger
    •  & Marcel M. M. Kuypers
  • Article
    | Open Access

    Here the authors show that 2-aminoethylphosphonate (2AEP) mineralisation is widespread in the global ocean, operating independently of exogenous inorganic phosphate concentration. They propose 2AEP may be a major route for the regeneration of phosphate required to support marine primary production.

    • Andrew R. J. Murphy
    • , David J. Scanlan
    •  & Ian D. E. A. Lidbury
  • Article
    | Open Access

    Plant and soil C:N:P ratios are critical to ecosystem functioning, but it remains uncertain how plant diversity affects terrestrial C:N:P. In this meta-analysis of 169 studies, the authors find that plant mixtures can balance plant and soil C:N:P ratios according to background soil C:N:P.

    • Xinli Chen
    •  & Han Y. H. Chen
  • Article
    | Open Access

    Relationships between biodiversity and phosphorus cycling and the underlying processes are complex. Here the authors analyse a biodiversity manipulation experiment and an agricultural management gradient to show how plant and mycorrhizal fungal diversity promote phosphorus exploitation.

    • Yvonne Oelmann
    • , Markus Lange
    •  & Wolfgang Wilcke
  • Article
    | Open Access

    Nitrogen fixation by diazotrophs is critical for marine primary production. Using Tara Oceans datasets, this study combines a quantitative image analysis pipeline with metagenomic mining to provide an improved global overview of diazotroph abundance, diversity and distribution.

    • Juan José Pierella Karlusich
    • , Eric Pelletier
    •  & Rachel A. Foster
  • Article
    | Open Access

    N2 fixation by heterotrophic bacteria has recently been found to take place on sinking marine particles, but an understanding of its regulation and importance is lacking. Here the authors develop a trait-based model for this N2 fixation, finding that this once overlooked process could have global importance.

    • Subhendu Chakraborty
    • , Ken H. Andersen
    •  & Lasse Riemann
  • Article
    | Open Access

    Some bacteriophage encode auxiliary metabolic genes (AMGs) that impact host metabolism and biogeochemical cycling during infection. Here the authors identify hundreds of AMGs in environmental phage encoding sulfur oxidation genes and use their global distribution to infer phage-mediated biogeochemical impacts.

    • Kristopher Kieft
    • , Zhichao Zhou
    •  & Karthik Anantharaman
  • Article
    | Open Access

    Primary productivity in the oligotrophic ocean sustains Earth’s ecosystems, but nutrient concentrations are vanishingly low. Here the authors measure nanomolar macronutrient concentrations in the North Pacific and find that net community production is sustained through high rates of phosphorus recycling.

    • Fuminori Hashihama
    • , Ichiro Yasuda
    •  & Masao Ishii
  • Article
    | Open Access

    The middle of the Gulf of Mexico is stratified and highly oligotrophic, yet there are anomalously high fluxes of sinking particulate matter from the euphotic zone. Here the authors show that lateral advection of organic matter supports nitrogen export in the Gulf of Mexico’s open ocean.

    • Thomas B. Kelly
    • , Angela N. Knapp
    •  & Michael R. Stukel
  • Article
    | Open Access

    Up to 40% of the ocean’s fixed nitrogen is lost in oxygen minimum zones (OMZs) by anammox, but despite the importance of this process, nitrogen loss patterns in OMZs are difficult to predict. Here the authors show that ammonium release from small particles is a major control of anammox in the Peruvian OMZ.

    • Clarissa Karthäuser
    • , Soeren Ahmerkamp
    •  & Marcel M. M. Kuypers
  • Article
    | Open Access

    Mercury is a neurotoxin and pollutant with enhanced emissions from anthropogenic activities. Here, the authors develop a global emissions, transport, and human risk model and find substantial future losses in revenue and public health if emission reductions proposed by the Minamata Convention are delayed.

    • Yanxu Zhang
    • , Zhengcheng Song
    •  & Ping Li
  • Article
    | Open Access

    The macroalgae Sargassum has grown for centuries in the oligotrophic North Atlantic supported by natural nutrient sources and cycling. Here the authors show that changes in tissue nutrient contents since the 1980s reflect global anthropogenic nitrogen enrichment, causing blooms in the wider Atlantic basin.

    • B. E. Lapointe
    • , R. A. Brewton
    •  & P. L. Morton
  • Article
    | Open Access

    A large fraction of ice sheet discharge enters the ocean subsurface from underneath large floating ice-tongues. Here the authors show that associated nutrient export may be governed by shelf circulation and, especially for Fe, particle-dissolved phase exchanges, which is largely independent from freshwater Fe content.

    • Stephan Krisch
    • , Mark James Hopwood
    •  & Eric Pieter Achterberg
  • Article
    | Open Access

    Expanded phosphorus availability possibly triggered a marine bioproduction boom after 2.3 billion years ago, but its delivery mechanisms remain unclear. Here we propose a kaolinite shuttle which efficiently adsorbs phosphorus in continental weathering settings and releases it under marine conditions.

    • Weiduo Hao
    • , Kaarel Mänd
    •  & Kurt O. Konhauser
  • Article
    | Open Access

    Microplastic pollution is a major threat to marine food webs, but the wider ranging impacts on global ocean biogeochemistry are poorly understood. Here the authors use an Earth system model to determine that zooplankton grazing on microplastics could exacerbate trends in ocean oxygen loss.

    • K. Kvale
    • , A. E. F. Prowe
    •  & A. Oschlies
  • Article
    | Open Access

    Ocean warming and changing circulation as a result of climate change are driving down oxygen levels and threatening ecosystems. Here the author shows that though immediate cessation of anthropogenic CO2 emissions would halt upper ocean oxygen loss, it would continue in the deep ocean for 100 s of years.

    • Andreas Oschlies
  • Article
    | Open Access

    Radioactive 137Cs is a fission product remaining in the environment from mid-20th century nuclear testing. Here the authors show that vegetation thousands of kilometers from testing sites continues to cycle 137Cs, and consequently, bees magnify this contaminant in honey in regions with low soil potassium.

    • J. M. Kaste
    • , P. Volante
    •  & A. J. Elmore
  • Article
    | Open Access

    Determining the origins of life on Earth is confounded by the fact that the sources of nutrients necessary to create early life forms remain mysterious. Here the authors show that lightning strikes could have supplied a major source of essential phosphorus on early Earth.

    • Benjamin L. Hess
    • , Sandra Piazolo
    •  & Jason Harvey
  • Article
    | Open Access

    The impacts of a melting Arctic on the biogeochemistry of marine ecosystems are unknown. Here, the authors investigate glacial input of iron to Svalbard fjords finding that reworking of glacial iron in fjord sediment is important to make iron bioavailable, but could be susceptible to glacial retreat.

    • Katja Laufer-Meiser
    • , Alexander B. Michaud
    •  & Bo Barker Jørgensen
  • Article
    | Open Access

    The deglaciation of Marinoan snowball Earth (~635 Myr ago) has been associated with potentially extensive CH4 emissions in relation to transient marine euxinia. Here, the authors find that active methanogenesis occurred during the termination of Marinoan snowball Earth, fueled by methyl sulfide production in sulfidic seawater.

    • Zhouqiao Zhao
    • , Bing Shen
    •  & Haoran Ma
  • Article
    | Open Access

    Southern Ocean productivity is a crucial component of the carbon cycle, but phytoplankton there are thought to be limited by iron. Here the authors conduct trace metal incubation experiments across the Drake Passage, finding that manganese can play an unexpected role in restricting phytoplankton growth.

    • Thomas J. Browning
    • , Eric P. Achterberg
    •  & Edward Mawji
  • Article
    | Open Access

    Enigmatic blooms of phytoplankton in aquatic oxygen-deficient zones could exacerbate depletion of nitrogen. Here the authors perform stable isotope experiments on the oxygen-deficient waters of Lake Tanganyika in Africa, finding that blooms drive down fixed nitrogen and could expand as a result of climate change.

    • Cameron M. Callbeck
    • , Benedikt Ehrenfels
    •  & Carsten J. Schubert
  • Article
    | Open Access

    Melting of the Greenland Ice Sheet—a threat for sea level rise—is accelerated by ice algal blooms. Here the authors find a link between mineral phosphorus and glacier algae, indicating that dust-derived nutrients aid bloom development, thereby impacting ice sheet melting.

    • Jenine McCutcheon
    • , Stefanie Lutz
    •  & Liane G. Benning
  • Article
    | Open Access

    The expansion of oceanic anoxia during the Paleocene Eocene Thermal Maximum has important implications for faunal turnover patterns and global biogeochemical cycles. Here the authors use uranium isotopes and a biogeochemical model to suggest that the areal expansion of anoxia must have been limited to 10-fold.

    • Matthew O. Clarkson
    • , Timothy M. Lenton
    •  & Derek Vance
  • Article
    | Open Access

    Constraining the rise in atmospheric oxygen through the early Earth is important to understand the evolution of complex life. Here, the authors find that a major rise in atmospheric oxygen level occurred after the Great Oxidation Event, followed by pO2 within 1% of present atmospheric level through most of the Proterozoic Eon (2.4 to 0.65 Ga).

    • Xiao-Ming Liu
    • , Linda C. Kah
    •  & Robert M. Hazen
  • Article
    | Open Access

    This study investigates in the importance of non-fossil fuel NOx emissions in the surface-earth-nitrogen cycle. The study shows how changes of regional human activities directly influence δ15N signatures of deposited NOx to terrestrial environments and that emissions have largely been underestimated.

    • Wei Song
    • , Xue-Yan Liu
    •  & Cong-Qiang Liu
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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
  • Article
    | Open Access

    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