Stable isotope analysis

  • 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

    The fate of soil carbon is controlled by plant inputs, microbial activity, and the soil matrix. Here the authors extend the notion of plant-derived particulate organic matter, from an easily available and labile carbon substrate, to a functional component at which persistence of soil carbon is determined.

    • Kristina Witzgall
    • , Alix Vidal
    •  & Carsten W. Mueller
  • 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

    The discovery of aerobic microbial communities in nutrient-poor sediments below the seafloor begs the question of the mechanisms for their persistence. Here the authors investigate subseafloor sediment in the South Pacific Gyre abyssal plain, showing that aerobic microbial life can be revived and retain metabolic potential even from 101.5 Ma-old sediment.

    • Yuki Morono
    • , Motoo Ito
    •  & Fumio Inagaki
  • Article
    | Open Access

    Non-traditional stable isotopes, such as of calcium, have potential to expand our understanding of ancient diets. Here, Martin et al. use stable calcium isotopes recovered from fossil tooth enamel to compare the dietary ecology of hominins and other primates in the Turkana Basin 2-4 million years ago.

    • Jeremy E. Martin
    • , Théo Tacail
    •  & Vincent Balter
  • Article
    | Open Access

    How the development of human societies is influenced through their ecological environment and climatic conditions has been the subject of intensive debate. Here, the authors present multi-proxy data from southern Scandinavia which suggests that pre-agricultural population growth there was likely influenced by enhanced marine production.

    • J. P. Lewis
    • , D. B. Ryves
    •  & S. Juggins
  • Article
    | Open Access

    The Paleocene-Eocene Thermal Maximum (c. 55 million years ago) was a period associated with massive carbon injection into the atmosphere, yet discrepancies in carbon isotope proxy records have led to substantial uncertainties in the source, scale, and timing of carbon emissions. Here, the authors propose that membrane lipids of marine planktonic archaea can reliably record the carbon isotope excursion and surface ocean warming, giving a new constraint for the source and size of the PETM carbon emissions.

    • Felix J. Elling
    • , Julia Gottschalk
    •  & Ann Pearson
  • Article
    | Open Access

    Global average, geographical distribution and temporal variations of the 13C isotopic signature of enteric fermentation emissions are not well understood. Here the authors established a global dataset and show a larger emission increase between the two periods (2002–2006 and 2008–2012) than previous studies.

    • Jinfeng Chang
    • , Shushi Peng
    •  & Philippe Bousquet
  • Article
    | Open Access

    Rising anthropogenic CO2 levels in the atmosphere are resulting in ocean acidification which may impact coral growth rates. Here, the authors quantify the relationship between water depth and δ13C compositions of South Pacific corals from the pre-industrial era, and their results should lead to improvements in the precision of sea level reconstructions using fossil corals.

    • Braddock K. Linsley
    • , Robert B. Dunbar
    •  & Gerard M. Wellington
  • Article
    | Open Access

    The effects of biological similarity on geochemical signals recorded in planktonic foraminiferal tests used in paleo-reconstructions remains unclear. Here, the authors embed species-specific vital effect offsets in evolutionary models and show how shared evolutionary history shapes δ13C, but not δ18O values.

    • Kirsty M. Edgar
    • , Pincelli M. Hull
    •  & Thomas H. G. Ezard
  • Article
    | Open Access

    Intrinsic water-use efficiency (W i ) reconstructions using tree rings often disregard developmental changes in W i as trees age. Here, the authors compare W i across varying tree sizes at a fixed CO2 level and show that ignoring developmental changes impacts conclusions on trees’ W i responses to CO2 or climate.

    • R. J. W. Brienen
    • , E. Gloor
    •  & M. Timonen
  • Article
    | Open Access

    Alluvial aquifers of river floodplains support abundant large-bodied consumers despite an absence of light and scarcity of organic carbon. DelVecchia et al. reveal that much of the biomass carbon in these freshwater consumers is ancient and derived from methane.

    • Amanda G. DelVecchia
    • , Jack A. Stanford
    •  & Xiaomei Xu
  • Article
    | Open Access

    Stable isotopes are a useful tool for distinguishing two sources in a mixture, but frequently systems have more than two components. Here, the authors propose a new approach to allow conclusive partitioning between three sources, still using only two stable isotopes, looking at soil CO2emissions.

    • Thea Whitman
    •  & Johannes Lehmann
  • Article
    | Open Access

    Before the mass extinction that characterized the Late Triassic period, there were a series of biotic turnover events, the cause of which are the subject of debate. Sato et al. present geochemical evidence in support of the theory that extraterrestrial impacts had an important role in these events.

    • Honami Sato
    • , Tetsuji Onoue
    •  & Katsuhiko Suzuki