Articles | Volume 18, issue 12
https://doi.org/10.5194/bg-18-3539-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-18-3539-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
17 Jun 2021
Research article |
| 17 Jun 2021
| 17 Jun 2021
High-resolution 14C bomb peak dating and climate response analyses of subseasonal stable isotope signals in wood of the African baobab – a case study from Oman
Franziska Slotta
Institute of Geological Sciences, Freie Universität Berlin,
Berlin, Germany
Section 4.3 Climate
Dynamics and Landscape Evolution, GFZ German Research Centre for Geosciences, Potsdam, Germany
Laboratory of Ion Beam Physics, ETH Zürich, Zurich,
Switzerland
Frank Riedel
Institute of Geological Sciences, Freie Universität Berlin,
Berlin, Germany
Karl-Uwe Heußner
Scientific Department of
the Head Office, Deutsches Archäologisches Institut, Berlin, Germany
Kai Hartmann
Institute of Geological Sciences, Freie Universität Berlin,
Berlin, Germany
Institute of Geological Sciences, Freie Universität Berlin,
Berlin, Germany
Section 4.3 Climate
Dynamics and Landscape Evolution, GFZ German Research Centre for Geosciences, Potsdam, Germany
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Luisa I. Minich, Dylan Geissbühler, Stefan Tobler, Annegret Udke, Alexander S. Brunmayr, Margaux Moreno Duborgel, Ciriaco McMackin, Lukas Wacker, Philip Gautschi, Negar Haghipour, Markus Egli, Ansgar Kahmen, Jens Leifeld, Timothy I. Eglinton, and Frank Hagedorn
EGUsphere, https://doi.org/10.5194/egusphere-2025-2267, https://doi.org/10.5194/egusphere-2025-2267, 2025
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We developed a framework using rates and 14C-derived ages of soil-respired CO2 and its sources (autotrophic, heterotrophic) to identify carbon cycling pathways in different land-use types. Rates, ages and sources of respired CO2 varied across forests, grasslands, croplands, and managed peatlands. Our results suggest that the relationship between rates and ages of respired CO2 serves as a robust indicator of carbon retention or destabilization from natural to disturbed systems.
Giulia Zazzeri, Lukas Wacker, Negar Haghipour, Philip Gautschi, Thomas Laemmel, Sönke Szidat, and Heather Graven
Atmos. Meas. Tech., 18, 319–325, https://doi.org/10.5194/amt-18-319-2025, https://doi.org/10.5194/amt-18-319-2025, 2025
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Radiocarbon (14C) is an optimal tracer of methane (CH4) emissions, as 14C measurements enable distinguishing between fossil methane and biogenic methane. However, these measurements are particularly challenging, mainly due to technical difficulties in the sampling procedure. We made the sample extraction much simpler and time efficient, providing a new technology that can be used by any research group, with the goal of expanding 14C measurements for an improved understanding of methane sources.
Viorica Nagavciuc, Gerhard Helle, Maria Rădoane, Cătălin-Constantin Roibu, Mihai-Gabriel Cotos, and Monica Ionita
Biogeosciences, 22, 55–69, https://doi.org/10.5194/bg-22-55-2025, https://doi.org/10.5194/bg-22-55-2025, 2025
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We reconstructed drought conditions for the past 200 years for central and eastern parts of Europe (Romania) using δ18O in oak tree ring cellulose from Romania, revealing periods of both extreme wetness (e.g., 1905–1915) and dryness (e.g., 1818–1835). The most severe droughts occurred in the 19th and 21st centuries, likely linked to large-scale atmospheric circulation. This research highlights the potential of tree rings to improve our understanding of long-term climate variability in Europe.
Viorica Nagavciuc, Simon L. L. Michel, Daniel F. Balting, Gerhard Helle, Mandy Freund, Gerhard H. Schleser, David N. Steger, Gerrit Lohmann, and Monica Ionita
Clim. Past, 20, 573–595, https://doi.org/10.5194/cp-20-573-2024, https://doi.org/10.5194/cp-20-573-2024, 2024
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The main aim of this paper is to present the summer vapor pressure deficit (VPD) reconstruction dataset for the last 400 years over Europe based on δ18O records by using a random forest approach. We provide both a spatial and a temporal long-term perspective on the past summer VPD and new insights into the relationship between summer VPD and large-scale atmospheric circulation. This is the first gridded reconstruction of the European summer VPD over the past 400 years.
Achim Brauer, Ingo Heinrich, Markus J. Schwab, Birgit Plessen, Brian Brademann, Matthias Köppl, Sylvia Pinkerneil, Daniel Balanzategui, Gerhard Helle, and Theresa Blume
DEUQUA Spec. Pub., 4, 41–58, https://doi.org/10.5194/deuquasp-4-41-2022, https://doi.org/10.5194/deuquasp-4-41-2022, 2022
Daniel Balting, Simon Michel, Viorica Nagavciuc, Gerhard Helle, Mandy Freund, Gerhard H. Schleser, David Steger, Gerrit Lohmann, and Monica Ionita
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2022-47, https://doi.org/10.5194/essd-2022-47, 2022
Preprint withdrawn
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Vapor pressure deficit is a key component of vegetation dynamics, soil science, meteorology, and soil science. In this study, we reconstruct the variability of the vapor pressure deficit in the past and examine the changes in future scenarios using climate models. In this way, past, present and future changes of the vapor pressure deficit can be detected locally, regionally, and continentally with higher statistical significance.
Caroline Welte, Jens Fohlmeister, Melina Wertnik, Lukas Wacker, Bodo Hattendorf, Timothy I. Eglinton, and Christoph Spötl
Clim. Past, 17, 2165–2177, https://doi.org/10.5194/cp-17-2165-2021, https://doi.org/10.5194/cp-17-2165-2021, 2021
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Stalagmites are valuable climate archives, but unlike other proxies the use of stable carbon isotopes (δ13C) is still difficult. A stalagmite from the Austrian Alps was analyzed using a new laser ablation method for fast radiocarbon (14C) analysis. This allowed 14C and δ13C to be combined, showing that besides soil and bedrock a third source is contributing during periods of warm, wet climate: old organic matter.
Daniel F. Balting, Monica Ionita, Martin Wegmann, Gerhard Helle, Gerhard H. Schleser, Norel Rimbu, Mandy B. Freund, Ingo Heinrich, Diana Caldarescu, and Gerrit Lohmann
Clim. Past, 17, 1005–1023, https://doi.org/10.5194/cp-17-1005-2021, https://doi.org/10.5194/cp-17-1005-2021, 2021
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To extend climate information back in time, we investigate the climate sensitivity of a δ18O network from tree rings, consisting of 26 European sites and covering the last 400 years. Our results suggest that the δ18O variability is associated with large-scale anomaly patterns that resemble those observed for the El Niño–Southern Oscillation. We conclude that the investigation of large-scale climate signals far beyond instrumental records can be done with a δ18O network derived from tree rings.
Ove H. Meisel, Joshua F. Dean, Jorien E. Vonk, Lukas Wacker, Gert-Jan Reichart, and Han Dolman
Biogeosciences, 18, 2241–2258, https://doi.org/10.5194/bg-18-2241-2021, https://doi.org/10.5194/bg-18-2241-2021, 2021
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Arctic permafrost lakes form thaw bulbs of unfrozen soil (taliks) beneath them where carbon degradation and greenhouse gas production are increased. We analyzed the stable carbon isotopes of Alaskan talik sediments and their porewater dissolved organic carbon and found that the top layers of these taliks are likely more actively degraded than the deeper layers. This in turn implies that these top layers are likely also more potent greenhouse gas producers than the underlying deeper layers.
Lisa Claire Orme, Xavier Crosta, Arto Miettinen, Dmitry V. Divine, Katrine Husum, Elisabeth Isaksson, Lukas Wacker, Rahul Mohan, Olivier Ther, and Minoru Ikehara
Clim. Past, 16, 1451–1467, https://doi.org/10.5194/cp-16-1451-2020, https://doi.org/10.5194/cp-16-1451-2020, 2020
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A record of past sea temperature in the Indian sector of the Southern Ocean, spanning the last 14 200 years, has been developed by analysis of fossil diatoms in marine sediment. During the late deglaciation the reconstructed temperature changes were highly similar to those over Antarctica, most likely due to a reorganisation of global ocean and atmospheric circulation. During the last 11 600 years temperatures gradually cooled and became increasingly variable.
Georg Schwamborn, Kai Hartmann, Bernd Wünnemann, Wolfgang Rösler, Annette Wefer-Roehl, Jörg Pross, Marlen Schlöffel, Franziska Kobe, Pavel E. Tarasov, Melissa A. Berke, and Bernhard Diekmann
Solid Earth, 11, 1375–1398, https://doi.org/10.5194/se-11-1375-2020, https://doi.org/10.5194/se-11-1375-2020, 2020
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We use a sediment core from the Gobi Desert (Ejina Basin, NW China) to illustrate the landscape history of the area. During 2.5 million years a sediment package of 223 m thickness has been accumulated. Various sediment types document that the area turned from a playa environment (shallow water environment with multiple flooding events) to an alluvial–fluvial environment after the arrival of the Heihe in the area. The river has been diverted due to tectonics.
Jan Erik Arndt, Robert D. Larter, Claus-Dieter Hillenbrand, Simon H. Sørli, Matthias Forwick, James A. Smith, and Lukas Wacker
The Cryosphere, 14, 2115–2135, https://doi.org/10.5194/tc-14-2115-2020, https://doi.org/10.5194/tc-14-2115-2020, 2020
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We interpret landforms on the seabed and investigate sediment cores to improve our understanding of the past ice sheet development in this poorly understood part of Antarctica. Recent crack development of the Brunt ice shelf has raised concerns about its stability and the security of the British research station Halley. We describe ramp-shaped bedforms that likely represent ice shelf grounding and stabilization locations of the past that may reflect an analogue to the process going on now.
Katrine Elnegaard Hansen, Jacques Giraudeau, Lukas Wacker, Christof Pearce, and Marit-Solveig Seidenkrantz
Clim. Past, 16, 1075–1095, https://doi.org/10.5194/cp-16-1075-2020, https://doi.org/10.5194/cp-16-1075-2020, 2020
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In this study, we present RainNet, a deep convolutional neural network for radar-based precipitation nowcasting, which was trained to predict continuous precipitation intensities at a lead time of 5 min. RainNet significantly outperformed the benchmark models at all lead times up to 60 min. Yet an undesirable property of RainNet predictions is the level of spatial smoothing. Obviously, RainNet learned an optimal level of smoothing to produce a nowcast at 5 min lead time.
Bryan C. Lougheed, Brett Metcalfe, Ulysses S. Ninnemann, and Lukas Wacker
Clim. Past, 14, 515–526, https://doi.org/10.5194/cp-14-515-2018, https://doi.org/10.5194/cp-14-515-2018, 2018
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Palaeoclimate reconstructions from deep-sea sediment archives provide valuable insight into past rapid climate change, but only a small proportion of the ocean is suitable for such reconstructions using the existing state of the art, i.e. the age–depth approach. We use dual radiocarbon (14C) and stable isotope analysis on single foraminifera to bypass the long-standing age–depth approach, thus facilitating past ocean chemistry reconstructions from vast, previously untapped ocean areas.
Liviu Giosan, Camilo Ponton, Muhammed Usman, Jerzy Blusztajn, Dorian Q. Fuller, Valier Galy, Negar Haghipour, Joel E. Johnson, Cameron McIntyre, Lukas Wacker, and Timothy I. Eglinton
Earth Surf. Dynam., 5, 781–789, https://doi.org/10.5194/esurf-5-781-2017, https://doi.org/10.5194/esurf-5-781-2017, 2017
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A reconstruction of erosion in the core monsoon zone of India provides unintuitive but fundamental insights: in contrast to semiarid regions that experience enhanced erosion during erratic rain events, the monsoon is annual and acts as a veritable
erosional pumpaccelerating when the land cover is minimal. The existence of such a monsoon erosional pump promises to reconcile conflicting views on the land–sea sediment and carbon transfer as well as the monsoon evolution on longer timescales.
Ulrike Dusek, Regina Hitzenberger, Anne Kasper-Giebl, Magdalena Kistler, Harro A. J. Meijer, Sönke Szidat, Lukas Wacker, Rupert Holzinger, and Thomas Röckmann
Atmos. Chem. Phys., 17, 3233–3251, https://doi.org/10.5194/acp-17-3233-2017, https://doi.org/10.5194/acp-17-3233-2017, 2017
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Measurements of the radioactive carbon isotope 14C allow to identify the sources of aerosol carbon. We report an extensive 14C source apportionment record in the Netherlands with samples covering a whole year. We discovered that long-range transport has a large influence on aerosol carbon levels. Fossil fuel carbon is least influenced by long-range transport and more regional in origin. Biomass burning seems to be a minor source of aerosol carbon in the Netherlands.
K. Schollaen, C. Karamperidou, P. Krusic, E. Cook, and G. Helle
Clim. Past, 11, 1325–1333, https://doi.org/10.5194/cp-11-1325-2015, https://doi.org/10.5194/cp-11-1325-2015, 2015
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Indonesia’s climate has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over Indonesia. In this study we investigate ENSO-related signals in a tree-ring δ18O record of Javanese teak. Our results reveal a clear influence of Warm Pool El Niño events on Javanese tree-ring δ18O. These results illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics.
K. Schollaen, H. Baschek, I. Heinrich, and G. Helle
Biogeosciences Discuss., https://doi.org/10.5194/bgd-12-11587-2015, https://doi.org/10.5194/bgd-12-11587-2015, 2015
Revised manuscript not accepted
E. Dietze, F. Maussion, M. Ahlborn, B. Diekmann, K. Hartmann, K. Henkel, T. Kasper, G. Lockot, S. Opitz, and T. Haberzettl
Clim. Past, 10, 91–106, https://doi.org/10.5194/cp-10-91-2014, https://doi.org/10.5194/cp-10-91-2014, 2014
Related subject area
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Fungi present distinguishable isotopic signals in their lipids when grown on glycolytic versus tricarboxylic acid cycle intermediates
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Stable iron isotope signals indicate a “pseudo-abiotic” process driving deep iron release in methanic sediments
Triple oxygen isotope evidence for the pathway of nitrous oxide production in a forested soil with increased emission on rainy days
Variability in oxygen isotopic fractionation of enzymatic O2 consumption
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How long does carbon stay in a near-pristine central Amazon forest? An empirical estimate with radiocarbon
No increase is detected and modeled for the seasonal cycle amplitude of δ13C of atmospheric carbon dioxide
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Position-specific kinetic isotope effects for nitrous oxide: a new expansion of the Rayleigh model
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Separating above-canopy CO2 and O2 measurements into their atmospheric and biospheric signatures
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Downpour dynamics: outsized impacts of storm events on unprocessed atmospheric nitrate export in an urban watershed
The hidden role of dissolved organic carbon in the biogeochemical cycle of carbon in modern redox-stratified lakes
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Determination of respiration and photosynthesis fractionation factors for atmospheric dioxygen inferred from a vegetation–soil–atmosphere analogue of the terrestrial biosphere in closed chambers
Permafrost degradation and nitrogen cycling in Arctic rivers: insights from stable nitrogen isotope studies
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Mineralization of autochthonous particulate organic carbon is a fast channel of organic matter turnover in Germany's largest drinking water reservoir
Carbon isotopic ratios of modern C3 and C4 vegetation on the Indian peninsula and changes along the plant–soil–river continuum – implications for vegetation reconstructions
Controls on nitrite oxidation in the upper Southern Ocean: insights from winter kinetics experiments in the Indian sector
Tracing the source of nitrate in a forested stream showing elevated concentrations during storm events
Intra-skeletal variability in phosphate oxygen isotope composition reveals regional heterothermies in marine vertebrates
Isotopic differences in soil–plant–atmosphere continuum composition and control factors of different vegetation zones on the northern slope of the Qilian Mountains
An analysis of the variability in δ13C in macroalgae from the Gulf of California: indicative of carbon concentration mechanisms and isotope discrimination during carbon assimilation
Summertime productivity and carbon export potential in the Weddell Sea, with a focus on the waters adjacent to Larsen C Ice Shelf
Particulate biogenic barium tracer of mesopelagic carbon remineralization in the Mediterranean Sea (PEACETIME project)
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Host-influenced geochemical signature in the parasitic foraminifera Hyrrokkin sarcophaga
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How are oxygen budgets influenced by dissolved iron and growth of oxygenic phototrophs in an iron-rich spring system? Initial results from the Espan Spring in Fürth, Germany
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Seasonality of nitrogen sources, cycling, and loading in a New England river discerned from nitrate isotope ratios
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Stanislav Jabinski, Vítězslav Kučera, Marek Kopáček, Jan Jansa, and Travis B. Meador
Biogeosciences, 22, 3127–3141, https://doi.org/10.5194/bg-22-3127-2025, https://doi.org/10.5194/bg-22-3127-2025, 2025
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Microbial production is a key parameter in estimation of organic matter cycling in environmental systems, and fungi play a major role as decomposers. In order to improve investigation of fungal production and turnover times in environmental studies, we determined the isotopic signals encoded into lipid biomarkers of fungal pure cultures growing on various carbon substrates in media with isotopically labeled water and bicarbonate.
Aymeric P. M. Servettaz, Yuta Isaji, Chisato Yoshikawa, Yanghee Jang, Boo-Keun Khim, Yeongjun Ryu, Daniel M. Sigman, Nanako O. Ogawa, Francisco J. Jiménez-Espejo, and Naohiko Ohkouchi
Biogeosciences, 22, 2239–2260, https://doi.org/10.5194/bg-22-2239-2025, https://doi.org/10.5194/bg-22-2239-2025, 2025
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Phytoplankton blooms occur after sea ice retreats in the Southern Ocean. In this study we investigate the influence of seasonal cycle of sea ice concentration on nitrate depletion, testing the hypothesis that meltwater release stabilizes the water column and favors nutrient utilization. We find that, at a regional scale, nitrate depletion and vertical mixing are weakly correlated with sea ice cycle. Nitrate depletion is rather linked to other oceanographic processes controlling mixing depth.
Jan Maier, Anna-Neva Visser, Christina Martina Schubert, Simon Thomas Wander, and Johannes Arthur Barth
EGUsphere, https://doi.org/10.5194/egusphere-2025-1580, https://doi.org/10.5194/egusphere-2025-1580, 2025
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We present the first large-scale assessment of the dissolved oxygen (DO) budget and δ18ODO across the Danube to distinguish DO sources and sinks, key for biogeochemical cycles. Two highly productive areas in the warm season showed large deviations (+12.1 ‰) from atmospheric equilibrium (+24.6 ‰ ± 0.4 ‰), unusual for large rivers. Critically low DO in the Sava (0.16 mmol/L) and lower Danube (0.2 mmol/L) in late summer resulted from intensified respiration.
Susann Henkel, Bo Liu, Michael Staubwasser, Simone A. Kasemann, Anette Meixner, David A. Aromokeye, Michael W. Friedrich, and Sabine Kasten
Biogeosciences, 22, 1673–1696, https://doi.org/10.5194/bg-22-1673-2025, https://doi.org/10.5194/bg-22-1673-2025, 2025
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We intend to unravel iron (Fe) reduction pathways in high-deposition methanic sediments because pools of Fe minerals could stimulate methane oxidation and also generation. Our data from the North Sea show that Fe release takes place mechanistically differently to Fe reduction in shallow sediments, which typically fractionates Fe isotopes. We conclude that fermentation of organic matter involving interspecies electron transfer, partly through conductive Fe oxides, could play an important role.
Weitian Ding, Urumu Tsunogai, Tianzheng Huang, Takashi Sambuichi, Wenhua Ruan, Masanori Ito, Hao Xu, Yongwon Kim, and Fumiko Nakagawa
EGUsphere, https://doi.org/10.21203/rs.3.rs-4264720/v2, https://doi.org/10.21203/rs.3.rs-4264720/v2, 2025
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Identifying the pathways of N2O produced through nitrification and denitrification in soil is crucial for effective mitigation. Thus, we monitored a new natural isotopic signature (Δ17O) of N2O in forested soil for identifying the pathways, which is almost stable during various biogeochemical processes. Our results suggest Δ17O is a promising signature for identifying pathways of N2O production, revealing that increased denitrification drives the high emission of N2O in soil on rainy days.
Carolina F.M. de Carvalho, Moritz F. Lehmann, and Sarah G. Pati
EGUsphere, https://doi.org/10.5194/egusphere-2025-1193, https://doi.org/10.5194/egusphere-2025-1193, 2025
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Using O2 stable isotope analysis, we determined the isotopic fractionation of biological O2 consumption by 10 flavin-dependent and 6 metalloenzymes. Metalloenzymes displayed a narrower range and lower values of isotopic fractionation than flavin-dependent enzymes. This work expands our understanding of the variability of oxygen isotopic fractionation at the enzyme level, improving the ability to study O2 dynamics from molecular to ecosystem scales.
Fawad Khan, Samuel Franco Luesma, Frederik Hartmann, Michael Dannenmann, Rainer Gasche, Clemens Scheer, Andreas Gattinger, Wiebke Niether, Elizabeth Gachibu Wangari, Ricky Mwangada Mwanake, Ralf Kiese, and Benjamin Wolf
EGUsphere, https://doi.org/10.5194/egusphere-2025-292, https://doi.org/10.5194/egusphere-2025-292, 2025
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Crop rotations with legumes and use of organic and mineral fertilizers show potential to reduce agricultural N losses. This study examined N losses, including direct N2 flux, on two adjacent sites with different management history: organic farming (OF) with legume cultivation and integrated farming (IF) using synthetic and organic N inputs. IF increased soil organic carbon and nitrogen content, 15N recovery and showed a balanced N budget, i.e., more efficient N cycling compared to OF.
Ingrid Chanca, Ingeborg Levin, Susan Trumbore, Kita Macario, Jost Lavric, Carlos Alberto Quesada, Alessandro Carioca de Araújo, Cléo Quaresma Dias Júnior, Hella van Asperen, Samuel Hammer, and Carlos A. Sierra
Biogeosciences, 22, 455–472, https://doi.org/10.5194/bg-22-455-2025, https://doi.org/10.5194/bg-22-455-2025, 2025
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Assessing the net carbon (C) budget of the Amazon entails considering the magnitude and timing of C absorption and losses through respiration (transit time of C). Radiocarbon-based estimates of the transit time of C in the Amazon Tall Tower Observatory (ATTO) suggest a change in the transit time from 6 ± 2 years and 18 ± 4 years within 2 years (October 2019 and December 2021, respectively). This variability indicates that only a fraction of newly fixed C can be stored for decades or longer.
Fortunat Joos, Sebastian Lienert, and Sönke Zaehle
Biogeosciences, 22, 19–39, https://doi.org/10.5194/bg-22-19-2025, https://doi.org/10.5194/bg-22-19-2025, 2025
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How plants regulate their exchange of CO2 and water with the atmosphere under global warming is critical for their carbon uptake and their cooling influence. We analyze the isotope ratio of atmospheric CO2 and detect no significant decadal trends in the seasonal cycle amplitude. The data are consistent with the regulation towards leaf CO2 and intrinsic water use efficiency growing proportionally to atmospheric CO2, in contrast to recent suggestions of downregulation of CO2 and water fluxes.
Weitian Ding, Urumu Tsunogai, and Fumiko Nakagawa
Biogeosciences, 21, 4717–4722, https://doi.org/10.5194/bg-21-4717-2024, https://doi.org/10.5194/bg-21-4717-2024, 2024
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Past studies have used the Δ17O of stream nitrate to estimate the gross nitrification rates (GNRs) in each forested catchment by approximating the Δ17O value of soil nitrate to be equal to that of stream nitrate. Based on inference and calculation of measured data, we found that this approximation resulted in an overestimated GNR. Therefore, it is essential to clarify and verify the Δ17O NO3− values in forested soils and streams before applying the Δ17O values of stream NO3− to GNR estimation.
Elise D. Rivett, Wenjuan Ma, Nathaniel E. Ostrom, and Eric L. Hegg
Biogeosciences, 21, 4549–4567, https://doi.org/10.5194/bg-21-4549-2024, https://doi.org/10.5194/bg-21-4549-2024, 2024
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Many different processes produce nitrous oxide (N2O), a potent greenhouse gas. Measuring the ratio of heavy and light nitrogen isotopes (15N/14N) for the non-exchangeable central and outer N atoms of N2O helps to distinguish sources of N2O. To accurately calculate the position-specific isotopic preference, we developed an expansion of the widely used Rayleigh model. Application of our new model to simulated and experimental data demonstrates its improved accuracy for analyzing N2O synthesis.
Eliza Harris, Philipp Fischer, Maciej P. Lewicki, Dominika Lewicka-Szczebak, Stephen J. Harris, and Fernando Perez-Cruz
Biogeosciences, 21, 3641–3663, https://doi.org/10.5194/bg-21-3641-2024, https://doi.org/10.5194/bg-21-3641-2024, 2024
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Greenhouse gases are produced and consumed via a number of pathways. Quantifying these pathways helps reduce the climate and environmental footprint of anthropogenic activities. The contribution of the pathways can be estimated from the isotopic composition, which acts as a fingerprint for these pathways. We have developed the Time-resolved FRactionation And Mixing Evaluation (TimeFRAME) model to simplify interpretation and estimate the contribution of different pathways and their uncertainty.
Kim A. P. Faassen, Jordi Vilà-Guerau de Arellano, Raquel González-Armas, Bert G. Heusinkveld, Ivan Mammarella, Wouter Peters, and Ingrid T. Luijkx
Biogeosciences, 21, 3015–3039, https://doi.org/10.5194/bg-21-3015-2024, https://doi.org/10.5194/bg-21-3015-2024, 2024
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The ratio between atmospheric O2 and CO2 can be used to characterize the carbon balance at the surface. By combining a model and observations from the Hyytiälä forest (Finland), we show that using atmospheric O2 and CO2 measurements from a single height provides a weak constraint on the surface CO2 exchange because large-scale processes such as entrainment confound this signal. We therefore recommend always using multiple heights of O2 and CO2 measurements to study surface CO2 exchange.
Nestor Gaviria-Lugo, Charlotte Läuchli, Hella Wittmann, Anne Bernhardt, Patrick Frings, Mahyar Mohtadi, Oliver Rach, and Dirk Sachse
Biogeosciences, 20, 4433–4453, https://doi.org/10.5194/bg-20-4433-2023, https://doi.org/10.5194/bg-20-4433-2023, 2023
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We analyzed how leaf wax hydrogen isotopes in continental and marine sediments respond to climate along one of the strongest aridity gradients in the world, from hyperarid to humid, along Chile. We found that under extreme aridity, the relationship between hydrogen isotopes in waxes and climate is non-linear, suggesting that we should be careful when reconstructing past hydrological changes using leaf wax hydrogen isotopes so as to avoid overestimating how much the climate has changed.
Ralf Conrad and Peter Claus
Biogeosciences, 20, 3625–3635, https://doi.org/10.5194/bg-20-3625-2023, https://doi.org/10.5194/bg-20-3625-2023, 2023
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Knowledge of carbon isotope fractionation is important for the assessment of the pathways involved in the degradation of organic matter. Propionate is an important intermediate. In the presence of sulfate, it was degraded by Syntrophobacter species via acetate to CO2. In the absence of sulfate, it was mainly consumed by Smithella and methanogenic archaeal species via butyrate and acetate to CH4. However, stable carbon isotope fractionation during the degradation process was quite small.
Alessandro Zanchetta, Linda M. J. Kooijmans, Steven van Heuven, Andrea Scifo, Hubertus A. Scheeren, Ivan Mammarella, Ute Karstens, Jin Ma, Maarten Krol, and Huilin Chen
Biogeosciences, 20, 3539–3553, https://doi.org/10.5194/bg-20-3539-2023, https://doi.org/10.5194/bg-20-3539-2023, 2023
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Carbonyl sulfide (COS) has been suggested as a tool to estimate carbon dioxide (CO2) uptake by plants during photosynthesis. However, understanding its sources and sinks is critical to preventing biases in this estimate. Combining observations and models, this study proves that regional sources occasionally influence the measurements at the 60 m tall Lutjewad tower (1 m a.s.l.; 53°24′ N, 6°21′ E) in the Netherlands. Moreover, it estimates nighttime COS fluxes to be −3.0 ± 2.6 pmol m−2 s−1.
Joel T. Bostic, David M. Nelson, and Keith N. Eshleman
Biogeosciences, 20, 2485–2498, https://doi.org/10.5194/bg-20-2485-2023, https://doi.org/10.5194/bg-20-2485-2023, 2023
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Land-use changes can affect water quality. We used tracers of pollution sources and water flow paths to show that an urban watershed exports variable sources during storm events relative to a less developed watershed. Our results imply that changing precipitation patterns combined with increasing urbanization may alter sources of pollution in the future.
Robin Havas, Christophe Thomazo, Miguel Iniesto, Didier Jézéquel, David Moreira, Rosaluz Tavera, Jeanne Caumartin, Elodie Muller, Purificación López-García, and Karim Benzerara
Biogeosciences, 20, 2405–2424, https://doi.org/10.5194/bg-20-2405-2023, https://doi.org/10.5194/bg-20-2405-2023, 2023
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Dissolved organic carbon (DOC) is a reservoir of prime importance in the C cycle of both continental and marine systems. It has also been suggested to influence the past Earth climate but is still poorly characterized in ancient-Earth-like environments. In this paper we show how DOC analyses from modern redox-stratified lakes can evidence specific metabolic reactions and environmental factors and how these can help us to interpret the C cycle of specific periods in the Earth's past.
Robin Havas, Christophe Thomazo, Miguel Iniesto, Didier Jézéquel, David Moreira, Rosaluz Tavera, Jeanne Caumartin, Elodie Muller, Purificación López-García, and Karim Benzerara
Biogeosciences, 20, 2347–2367, https://doi.org/10.5194/bg-20-2347-2023, https://doi.org/10.5194/bg-20-2347-2023, 2023
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We describe the C cycle of four modern stratified water bodies from Mexico, a necessary step to better understand the C cycle of primitive-Earth-like environments, which were dominated by these kinds of conditions. We highlight the importance of local external factors on the C cycle of these systems. Notably, they influence the sensitivity of the carbonate record to environmental changes. We also show the strong C-cycle variability among these lakes and their organic C sediment record.
Yifan Ma, Kuanbo Zhou, Weifang Chen, Junhui Chen, Jin-Yu Terence Yang, and Minhan Dai
Biogeosciences, 20, 2013–2030, https://doi.org/10.5194/bg-20-2013-2023, https://doi.org/10.5194/bg-20-2013-2023, 2023
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We distinguished particulate organic carbon (POC) export fluxes out of the nutrient-depleted layer (NDL) and the euphotic zone. The amount of POC export flux at the NDL base suggests that the NDL could be a hotspot of particle export. The substantial POC export flux at the NDL base challenges traditional concepts that the NDL was limited in terms of POC export. The dominant nutrient source for POC export fluxes should be subsurface nutrients, which was determined by 15N isotopic mass balance.
Clémence Paul, Clément Piel, Joana Sauze, Nicolas Pasquier, Frédéric Prié, Sébastien Devidal, Roxanne Jacob, Arnaud Dapoigny, Olivier Jossoud, Alexandru Milcu, and Amaëlle Landais
Biogeosciences, 20, 1047–1062, https://doi.org/10.5194/bg-20-1047-2023, https://doi.org/10.5194/bg-20-1047-2023, 2023
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To improve the interpretation of the δ18Oatm and Δ17O of O2 in air bubbles in ice cores, we need to better quantify the oxygen fractionation coefficients associated with biological processes. We performed a simplified analogue of the terrestrial biosphere in a closed chamber. We found a respiration fractionation in agreement with the previous estimates at the microorganism scale, and a terrestrial photosynthetic fractionation was found. This has an impact on the estimation of the Dole effect.
Adam Francis, Raja S. Ganeshram, Robyn E. Tuerena, Robert G. M. Spencer, Robert M. Holmes, Jennifer A. Rogers, and Claire Mahaffey
Biogeosciences, 20, 365–382, https://doi.org/10.5194/bg-20-365-2023, https://doi.org/10.5194/bg-20-365-2023, 2023
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Climate change is causing extensive permafrost degradation and nutrient releases into rivers with great ecological impacts on the Arctic Ocean. We focused on nitrogen (N) release from this degradation and associated cycling using N isotopes, an understudied area. Many N species are released at degradation sites with exchanges between species. N inputs from permafrost degradation and seasonal river N trends were identified using isotopes, helping to predict climate change impacts.
Mohamed Ayache, Jean-Claude Dutay, Kazuyo Tachikawa, Thomas Arsouze, and Catherine Jeandel
Biogeosciences, 20, 205–227, https://doi.org/10.5194/bg-20-205-2023, https://doi.org/10.5194/bg-20-205-2023, 2023
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The neodymium (Nd) is one of the most useful tracers to fingerprint water mass provenance. However, the use of Nd is hampered by the lack of adequate quantification of the external sources. Here, we present the first simulation of dissolved Nd concentration and Nd isotopic composition in the Mediterranean Sea using a high-resolution model. We aim to better understand how the various external sources affect the Nd cycle and particularly assess how it is impacted by atmospheric inputs.
Marta Santos-Garcia, Raja S. Ganeshram, Robyn E. Tuerena, Margot C. F. Debyser, Katrine Husum, Philipp Assmy, and Haakon Hop
Biogeosciences, 19, 5973–6002, https://doi.org/10.5194/bg-19-5973-2022, https://doi.org/10.5194/bg-19-5973-2022, 2022
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Terrestrial sources of nitrate are important contributors to the nutrient pool in the fjords of Kongsfjorden and Rijpfjorden in Svalbard during the summer, and they sustain most of the fjord primary productivity. Ongoing tidewater glacier retreat is postulated to favour light limitation and less dynamic circulation in fjords. This is suggested to encourage the export of nutrients to the middle and outer part of the fjord system, which may enhance primary production within and in offshore areas.
Marlene Dordoni, Michael Seewald, Karsten Rinke, Kurt Friese, Robert van Geldern, Jakob Schmidmeier, and Johannes A. C. Barth
Biogeosciences, 19, 5343–5355, https://doi.org/10.5194/bg-19-5343-2022, https://doi.org/10.5194/bg-19-5343-2022, 2022
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Organic matter (OM) turnover into dissolved inorganic carbon (DIC) was investigated by means of carbon isotope mass balances in Germany's largest water reservoir. This includes a metalimnetic oxygen minimum (MOM). Autochthonous particulate organic carbon (POC) was the main contributor to DIC, with rates that were highest for the MOM. Generally low turnover rates outline the environmental fragility of this water body in the case that OM loads increase due to storm events or land use changes.
Frédérique M. S. A. Kirkels, Hugo J. de Boer, Paulina Concha Hernández, Chris R. T. Martes, Marcel T. J. van der Meer, Sayak Basu, Muhammed O. Usman, and Francien Peterse
Biogeosciences, 19, 4107–4127, https://doi.org/10.5194/bg-19-4107-2022, https://doi.org/10.5194/bg-19-4107-2022, 2022
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The distinct carbon isotopic values of C3 and C4 plants are widely used to reconstruct past hydroclimate, where more C3 plants reflect wetter and C4 plants drier conditions. Here we examine the impact of regional hydroclimatic conditions on plant isotopic values in the Godavari River basin, India. We find that it is crucial to identify regional plant isotopic values and consider drought stress, which introduces a bias in C3 / C4 plant estimates and associated hydroclimate reconstructions.
Mhlangabezi Mdutyana, Tanya Marshall, Xin Sun, Jessica M. Burger, Sandy J. Thomalla, Bess B. Ward, and Sarah E. Fawcett
Biogeosciences, 19, 3425–3444, https://doi.org/10.5194/bg-19-3425-2022, https://doi.org/10.5194/bg-19-3425-2022, 2022
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Nitrite-oxidizing bacteria in the winter Southern Ocean show a high affinity for nitrite but require a minimum (i.e., "threshold") concentration before they increase their rates of nitrite oxidation significantly. The classic Michaelis–Menten model thus cannot be used to derive the kinetic parameters, so a modified equation was employed that also yields the threshold nitrite concentration. Dissolved iron availability may play an important role in limiting nitrite oxidation.
Weitian Ding, Urumu Tsunogai, Fumiko Nakagawa, Takashi Sambuichi, Hiroyuki Sase, Masayuki Morohashi, and Hiroki Yotsuyanagi
Biogeosciences, 19, 3247–3261, https://doi.org/10.5194/bg-19-3247-2022, https://doi.org/10.5194/bg-19-3247-2022, 2022
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Excessive leaching of nitrate from forested catchments during storm events degrades water quality and causes eutrophication in downstream areas. Thus, tracing the source of nitrate increase during storm events in forested streams is important for sustainable forest management. Based on the isotopic compositions of stream nitrate, including Δ17O, this study clarifies that the source of stream nitrate increase during storm events was soil nitrate in the riparian zone.
Nicolas Séon, Romain Amiot, Guillaume Suan, Christophe Lécuyer, François Fourel, Fabien Demaret, Arnauld Vinçon-Laugier, Sylvain Charbonnier, and Peggy Vincent
Biogeosciences, 19, 2671–2681, https://doi.org/10.5194/bg-19-2671-2022, https://doi.org/10.5194/bg-19-2671-2022, 2022
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We analysed the oxygen isotope composition of bones and teeth of four marine species possessing regional heterothermies. We observed a consistent link between oxygen isotope composition and temperature heterogeneities recorded by classical methods. This opens up new perspectives on the determination of the thermoregulatory strategies of extant marine vertebrates where conventional methods are difficult to apply, but also allows us to investigate thermophysiologies of extinct vertebrates.
Yuwei Liu, Guofeng Zhu, Zhuanxia Zhang, Zhigang Sun, Leilei Yong, Liyuan Sang, Lei Wang, and Kailiang Zhao
Biogeosciences, 19, 877–889, https://doi.org/10.5194/bg-19-877-2022, https://doi.org/10.5194/bg-19-877-2022, 2022
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We took the water cycle process of soil–plant–atmospheric precipitation as the research objective. In the water cycle of soil–plant–atmospheric precipitation, precipitation plays the main controlling role. The main source of replenishment for alpine meadow plants is precipitation and alpine meltwater; the main source of replenishment for forest plants is soil water; and the plants in the arid foothills mainly use groundwater.
Roberto Velázquez-Ochoa, María Julia Ochoa-Izaguirre, and Martín Federico Soto-Jiménez
Biogeosciences, 19, 1–27, https://doi.org/10.5194/bg-19-1-2022, https://doi.org/10.5194/bg-19-1-2022, 2022
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Our research is the first approximation to understand the δ13C macroalgal variability in one of the most diverse marine ecosystems in the world, the Gulf of California. The life-form is the principal cause of δ13C macroalgal variability, mainly taxonomy. However, changes in habitat characteristics and environmental conditions also influence the δ13C macroalgal variability. The δ13C macroalgae is indicative of carbon concentration mechanisms and isotope discrimination during carbon assimilation.
Raquel F. Flynn, Thomas G. Bornman, Jessica M. Burger, Shantelle Smith, Kurt A. M. Spence, and Sarah E. Fawcett
Biogeosciences, 18, 6031–6059, https://doi.org/10.5194/bg-18-6031-2021, https://doi.org/10.5194/bg-18-6031-2021, 2021
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Biological activity in the shallow Weddell Sea affects the biogeochemistry of recently formed deep waters. To investigate the drivers of carbon and nutrient export, we measured rates of primary production and nitrogen uptake, characterized the phytoplankton community, and estimated nutrient depletion ratios across the under-sampled western Weddell Sea in mid-summer. Carbon export was highest at the ice shelves and was determined by a combination of physical, chemical, and biological factors.
Stéphanie H. M. Jacquet, Christian Tamburini, Marc Garel, Aurélie Dufour, France Van Vambeke, Frédéric A. C. Le Moigne, Nagib Bhairy, and Sophie Guasco
Biogeosciences, 18, 5891–5902, https://doi.org/10.5194/bg-18-5891-2021, https://doi.org/10.5194/bg-18-5891-2021, 2021
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We compared carbon remineralization rates (MRs) in the western and central Mediterranean Sea in late spring during the PEACETIME cruise, as assessed using the barium tracer. We reported higher and deeper (up to 1000 m depth) MRs in the western basin, potentially sustained by an additional particle export event driven by deep convection. The central basin is the site of a mosaic of blooming and non-blooming water masses and showed lower MRs that were restricted to the upper mesopelagic layer.
Shinsuke Kawagucci, Yohei Matsui, Akiko Makabe, Tatsuhiro Fukuba, Yuji Onishi, Takuro Nunoura, and Taichi Yokokawa
Biogeosciences, 18, 5351–5362, https://doi.org/10.5194/bg-18-5351-2021, https://doi.org/10.5194/bg-18-5351-2021, 2021
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Hydrogen and carbon isotope ratios of methane as well as the relevant biogeochemical parameters and microbial community compositions in hydrothermal plumes in the Okinawa Trough were observed. We succeeded in simultaneously determining hydrogen and carbon isotope fractionation factors associated with aerobic oxidation of methane in seawater (εH = 49.4 ± 5.0 ‰, εC = 5.2 ± 0.4 ‰) – the former being the first of its kind ever reported.
Nicolai Schleinkofer, David Evans, Max Wisshak, Janina Vanessa Büscher, Jens Fiebig, André Freiwald, Sven Härter, Horst R. Marschall, Silke Voigt, and Jacek Raddatz
Biogeosciences, 18, 4733–4753, https://doi.org/10.5194/bg-18-4733-2021, https://doi.org/10.5194/bg-18-4733-2021, 2021
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We have measured the chemical composition of the carbonate shells of the parasitic foraminifera Hyrrokkin sarcophaga in order to test if it is influenced by the host organism (bivalve or coral). We find that both the chemical and isotopic composition is influenced by the host organism. For example strontium is enriched in foraminifera that grew on corals, whose skeleton is built from aragonite, which is naturally enriched in strontium compared to the bivalves' calcite shell.
Lena Rohe, Traute-Heidi Anderson, Heinz Flessa, Anette Goeske, Dominika Lewicka-Szczebak, Nicole Wrage-Mönnig, and Reinhard Well
Biogeosciences, 18, 4629–4650, https://doi.org/10.5194/bg-18-4629-2021, https://doi.org/10.5194/bg-18-4629-2021, 2021
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This is the first experimental setup combining a complex set of methods (microbial inhibitors and isotopic approaches) to differentiate between N2O produced by fungi or bacteria during denitrification in three soils. Quantifying the fungal fraction with inhibitors was not successful due to large amounts of uninhibited N2O production. All successful methods suggested a small or missing fungal contribution. Artefacts occurring with microbial inhibition to determine N2O fluxes are discussed.
Inga Köhler, Raul E. Martinez, David Piatka, Achim J. Herrmann, Arianna Gallo, Michelle M. Gehringer, and Johannes A. C. Barth
Biogeosciences, 18, 4535–4548, https://doi.org/10.5194/bg-18-4535-2021, https://doi.org/10.5194/bg-18-4535-2021, 2021
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We investigated how high Fe(II) levels influence the O2 budget of a circum-neutral Fe(II)-rich spring and if a combined study of dissolved O (DO) and its isotopic composition can help assess this effect. We showed that dissolved Fe(II) can exert strong effects on the δ18ODO even though a constant supply of atmospheric O2 occurs. In the presence of photosynthesis, direct effects of Fe oxidation become masked. Critical Fe(II) concentrations indirectly control the DO by enhancing photosynthesis.
Owen A. Sherwood, Samuel H. Davin, Nadine Lehmann, Carolyn Buchwald, Evan N. Edinger, Moritz F. Lehmann, and Markus Kienast
Biogeosciences, 18, 4491–4510, https://doi.org/10.5194/bg-18-4491-2021, https://doi.org/10.5194/bg-18-4491-2021, 2021
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Pacific water flowing eastward through the Canadian Arctic plays an important role in redistributing nutrients to the northwest Atlantic Ocean. Using samples collected from northern Baffin Bay to the southern Labrador Shelf, we show that stable isotopic ratios in seawater nitrate reflect the fraction of Pacific to Atlantic water. These results provide a new framework for interpreting patterns of nitrogen isotopic variability recorded in modern and archival organic materials in the region.
Peter M. J. Douglas, Emerald Stratigopoulos, Sanga Park, and Dawson Phan
Biogeosciences, 18, 3505–3527, https://doi.org/10.5194/bg-18-3505-2021, https://doi.org/10.5194/bg-18-3505-2021, 2021
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Hydrogen isotopes could be a useful tool to help resolve the geographic distribution of methane emissions from freshwater environments. We analyzed an expanded global dataset of freshwater methane hydrogen isotope ratios and found significant geographic variation linked to water isotopic composition. This geographic variability could be used to resolve changing methane fluxes from freshwater environments and provide more accurate estimates of the relative balance of global methane sources.
Veronica R. Rollinson, Julie Granger, Sydney C. Clark, Mackenzie L. Blanusa, Claudia P. Koerting, Jamie M. P. Vaudrey, Lija A. Treibergs, Holly C. Westbrook, Catherine M. Matassa, Meredith G. Hastings, and Craig R. Tobias
Biogeosciences, 18, 3421–3444, https://doi.org/10.5194/bg-18-3421-2021, https://doi.org/10.5194/bg-18-3421-2021, 2021
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We measured nutrients and the naturally occurring nitrogen (N) and oxygen (O) stable isotope ratios of nitrate discharged from a New England river over an annual cycle, to monitor N loading and identify dominant sources from the watershed. We uncovered a seasonality to loading and sources of N from the watershed. Seasonality in the nitrate isotope ratios also informed on N cycling, conforming to theoretical expectations of riverine nutrient cycling.
Zixun Chen, Xuejun Liu, Xiaoqing Cui, Yaowen Han, Guoan Wang, and Jiazhu Li
Biogeosciences, 18, 2859–2870, https://doi.org/10.5194/bg-18-2859-2021, https://doi.org/10.5194/bg-18-2859-2021, 2021
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δ13C in plants is a sensitive long-term indicator of physiological acclimatization. The present study suggests that precipitation change and increasing atmospheric N deposition have little impact on δ13C of H. ammodendron, a dominant plant in central Asian deserts, but affect its gas exchange. In addition, this study shows that δ13C of H. ammodendron could not indicate its water use efficiency (WUE), suggesting that whether δ13C of C4 plants indicates WUE is species-specific.
Petra Zahajská, Carolina Olid, Johanna Stadmark, Sherilyn C. Fritz, Sophie Opfergelt, and Daniel J. Conley
Biogeosciences, 18, 2325–2345, https://doi.org/10.5194/bg-18-2325-2021, https://doi.org/10.5194/bg-18-2325-2021, 2021
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The drivers of high accumulation of single-cell siliceous algae (diatoms) in a high-latitude lake have not been fully characterized before. We studied silicon cycling of the lake through water, radon, silicon, and stable silicon isotope balances. Results showed that groundwater brings 3 times more water and dissolved silica than the stream inlet. We demonstrate that groundwater discharge and low sediment deposition have driven the high diatom accumulation in the studied lake in the past century.
Yu-Te Hsieh, Walter Geibert, E. Malcolm S. Woodward, Neil J. Wyatt, Maeve C. Lohan, Eric P. Achterberg, and Gideon M. Henderson
Biogeosciences, 18, 1645–1671, https://doi.org/10.5194/bg-18-1645-2021, https://doi.org/10.5194/bg-18-1645-2021, 2021
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The South Atlantic near 40° S is one of the high-productivity and most dynamic nutrient regions in the oceans, but the sources and fluxes of trace elements (TEs) to this region remain unclear. This study investigates seawater Ra-228 and provides important constraints on ocean mixing and dissolved TE fluxes to this region. Vertical mixing is a more important source than aeolian or shelf inputs in this region, but particulate or winter deep-mixing inputs may be required to balance the TE budgets.
Zhongjie Yu and Emily M. Elliott
Biogeosciences, 18, 805–829, https://doi.org/10.5194/bg-18-805-2021, https://doi.org/10.5194/bg-18-805-2021, 2021
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In this study, we demonstrated distinct nitrogen isotope effects for nitric oxide (NO) production from major microbial and chemical NO sources in an agricultural soil. These results highlight characteristic bond-forming and breaking mechanisms associated with microbial and chemical NO production and implicate that simultaneous isotopic analyses of NO and nitrous oxide (N2O) can lead to unprecedented insights into the sources and processes controlling NO and N2O emissions from agricultural soils.
Daniel A. Frick, Rainer Remus, Michael Sommer, Jürgen Augustin, Danuta Kaczorek, and Friedhelm von Blanckenburg
Biogeosciences, 17, 6475–6490, https://doi.org/10.5194/bg-17-6475-2020, https://doi.org/10.5194/bg-17-6475-2020, 2020
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Silicon is taken up by some plants to increase structural stability and to develop stress resistance and is rejected by others. To explore the underlying mechanisms, we used the stable isotopes of silicon that shift in their relative abundance depending on the biochemical transformation involved. On species with a rejective (tomato, mustard) and active (wheat) uptake mechanism, grown in hydroculture, we found that the transport of silicic acid is controlled by the precipitation of biogenic opal.
Quentin Charbonnier, Julien Bouchez, Jérôme Gaillardet, and Éric Gayer
Biogeosciences, 17, 5989–6015, https://doi.org/10.5194/bg-17-5989-2020, https://doi.org/10.5194/bg-17-5989-2020, 2020
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The abundance and isotope composition of the trace metal barium (Ba) allows us to track and quantify nutrient cycling throughout the Amazon Basin. In particular, we show that the Ba biological fingerprint evolves from that of a strong net nutrient uptake in the mountainous area of the Andes towards efficient nutrient recycling on the plains of the Lower Amazon. Our study highlights the fact that the geochemical signature of rock-derived nutrients transported by the Amazon is scarred by life.
Ajinkya G. Deshpande, Thomas W. Boutton, Ayumi Hyodo, Charles W. Lafon, and Georgianne W. Moore
Biogeosciences, 17, 5639–5653, https://doi.org/10.5194/bg-17-5639-2020, https://doi.org/10.5194/bg-17-5639-2020, 2020
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Wetland forests in the southern USA are threatened by changing climate and human-induced pressures. We used tree ring widths and C isotopes as indicators of forest growth and physiological stress, respectively, and compared these to past climate data. We observed that vegetation growing in the drier patches is susceptible to stress, while vegetation growth and physiology in wetter patches is less sensitive to unfavorable environmental conditions, highlighting the importance of optimal wetness.
Dominika Lewicka-Szczebak, Maciej Piotr Lewicki, and Reinhard Well
Biogeosciences, 17, 5513–5537, https://doi.org/10.5194/bg-17-5513-2020, https://doi.org/10.5194/bg-17-5513-2020, 2020
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We present the first validation of N2O isotopic approaches for estimating N2O source pathways and N2O reduction. These approaches are widely used for tracing soil nitrogen cycling, but the results of these estimations are very uncertain. Here we report the results from parallel treatments allowing for precise validation of these approaches, and we propose the best strategies for results interpretation, including the new idea of an isotope model integrating three isotopic signatures of N2O.
Markus Raitzsch, Claire Rollion-Bard, Ingo Horn, Grit Steinhoefel, Albert Benthien, Klaus-Uwe Richter, Matthieu Buisson, Pascale Louvat, and Jelle Bijma
Biogeosciences, 17, 5365–5375, https://doi.org/10.5194/bg-17-5365-2020, https://doi.org/10.5194/bg-17-5365-2020, 2020
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The isotopic composition of boron in carbonate shells of marine unicellular organisms is a popular tool to estimate seawater pH. Usually, many shells need to be dissolved and measured for boron isotopes, but the information on their spatial distribution is lost. Here, we investigate two techniques that allow for measuring boron isotopes within single shells and show that they yield robust mean values but provide additional information on the heterogeneity within and between single shells.
Florian Einsiedl, Anja Wunderlich, Mathieu Sebilo, Ömer K. Coskun, William D. Orsi, and Bernhard Mayer
Biogeosciences, 17, 5149–5161, https://doi.org/10.5194/bg-17-5149-2020, https://doi.org/10.5194/bg-17-5149-2020, 2020
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Nitrate pollution of freshwaters and methane emissions into the atmosphere are crucial factors in deteriorating the quality of drinking water and in contributing to global climate change. Here, we report vertical concentration and stable isotope profiles of CH4, NO3-, NO2-, and NH4+ in the water column of Fohnsee (southern Bavaria, Germany) that may indicate linkages between nitrate-dependent anaerobic methane oxidation and the anaerobic oxidation of ammonium.
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Short summary
The African baobab is a challenging climate and environmental archive for its semi-arid habitat due to dating uncertainties and parenchyma-rich wood anatomy. Annually resolved F14C data of tree-ring cellulose (1941–2005) from a tree in Oman show the annual character of the baobab’s growth rings but were up to 8.8 % lower than expected for 1964–1967. Subseasonal δ13C and δ18O patterns reveal years with low average monsoon rain as well as heavy rainfall events from pre-monsoonal cyclones.
The African baobab is a challenging climate and environmental archive for its semi-arid habitat...
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