Articles | Volume 23, issue 5
https://doi.org/10.5194/bg-23-1987-2026
© Author(s) 2026. 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-23-1987-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
17 Mar 2026
Research article |
| 17 Mar 2026
| 17 Mar 2026
The distribution and isotopomeric characterization of nitrous oxide in the Eastern Gotland Basin (central Baltic Sea)
Pratirupa Bardhan
CORRESPONDING AUTHOR
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1–3, 24148 Kiel, Germany
now at: Dept of Geology and Environmental Science, University of Pittsburgh, 4107 O' Hara St, PA 15260, USA
Claudia Frey
Department of Environmental Sciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland
Gregor Rehder
Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Seestr. 15, 18119 Rostock, Germany
Hermann W. Bange
GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1–3, 24148 Kiel, Germany
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Ina Stoltenberg, Lea Lange, and Hermann W. Bange
Biogeosciences, 23, 1515–1525, https://doi.org/10.5194/bg-23-1515-2026, https://doi.org/10.5194/bg-23-1515-2026, 2026
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In order to decipher the effect of a phytoplankton bloom on N2O, dissolved N2O was measured in the upper 1 mm of the water column (seasurface microlayer) and in the underlying water during a mesocosm study. N2O concentrations were slightly enriched in the microlayer compared to the underlying water and were apparently not affected by irradiation and a phytoplankton bloom. Our results indicate that the role of the surface microlayer for N2O cycling has been overlooked so far.
Lina A. Holthusen, Hermann W. Bange, Thomas H. Badewien, Julia C. Muchowski, Tina Santl-Temkiv, Jennie Spicker Schmidt, Oliver Wurl, and Damian L. Arévalo-Martínez
The Cryosphere, 20, 535–550, https://doi.org/10.5194/tc-20-535-2026, https://doi.org/10.5194/tc-20-535-2026, 2026
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In spring 2023, in the Fram Strait, we investigated the near-surface distribution of the greenhouse gases methane and nitrous oxide in open leads and under sea ice to address the lack of observations in the Arctic Ocean. The study area acted as a source for both gases, and the onset of sea ice melt affected their concentrations and emissions. Surface-active substances accumulated in the sea-surface microlayer of open leads during an algal bloom, potentially attenuating greenhouse gas emissions.
Yuanxu Dong, Christa A. Marandino, Ryo Dobashi, David Ho, Gregor Rehder, Henry C. Bittig, Josefine Karnatz, Bita Sabbaghzadeh, Helen Czerski, and Anja Engel
EGUsphere, https://doi.org/10.5194/egusphere-2025-6095, https://doi.org/10.5194/egusphere-2025-6095, 2026
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Air-sea gas exchange regulates the Earth's climate. However, the kinetic exchange process only uses wind speed to describe, neglecting other drivers. In this study, we investigate how fetch and natural surfactants modulate the air-sea carbon dioxide exchange. Measurements from the central Baltic Sea show that limited fetch and elevated surfactants significantly suppress this exchange. A new parameterization is provided, improving regional carbon budgets and evaluations of climate solutions.
Joachim Schönfeld, Hermann W. Bange, Helmke Hepach, and Svenja Reents
Biogeosciences, 23, 421–440, https://doi.org/10.5194/bg-23-421-2026, https://doi.org/10.5194/bg-23-421-2026, 2026
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The current state of intertidal waters at Bottsand lagoon on the Baltic Sea coast, and on the mudflats off Schobüll on the North Sea coast of Schleswig-Holstein, Germany was assessed with a 36-month time series of water level, temperature, and salinity measurements. Periods of strong precipitation, high Elbe river discharge, and high solar radiation caused a higher data variability as compared to the off shore monitoring stations Boknis Eck in the Baltic and Sylt Roads in the North Sea.
Alessandra Mazzoli, Peter Reichert, Claudia Frey, Cameron M. Callbeck, Tim J. Paulus, Jakob Zopfi, and Moritz F. Lehmann
Biogeosciences, 23, 283–314, https://doi.org/10.5194/bg-23-283-2026, https://doi.org/10.5194/bg-23-283-2026, 2026
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Nitrogen (re-)cycling in sediments plays a key role in aquatic environments, but involves many overlapping biogeochemical processes that are hard to separate. We developed a new comprehensive sedimentary nitrogen isotope model to disentangle these reactions. Using field data from a Swiss lake and statistical tools, we demonstrated the robustness and validity of our modelling framework for a broad range of applications.
Lea Lange, Dennis Booge, Hendrik Feil, Josefine Karnatz, Ina Stoltenberg, Hermann W. Bange, and Christa A. Marandino
EGUsphere, https://doi.org/10.5194/egusphere-2025-5361, https://doi.org/10.5194/egusphere-2025-5361, 2025
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Many gases formed and destroyed in the ocean influence climate and air quality, with evidence that these processes also happen in the skin of the ocean. Studies of this thin upper layer use specialized sampling equipment, which is known to cause losses of the gases. We performed lab experiments to quantify these losses for three gases and found that 13 % remain after sampling. With further tests, our results can be used to obtain reliable gas measurements in the field, which have been elusive.
Florian Börgel, Itzel Ruvalcaba Baroni, Leonie Barghorn, Leonard Borchert, Bronwyn Cahill, Cyril Dutheil, Leonie Esters, Malgorzata Falarz, Helena L. Filipsson, Matthias Gröger, Jari Hänninen, Magnus Hieronymus, Erko Jakobsen, Mehdi Pasha Karami, Karol Kulinski, Taavi Liblik, H. E. Markus Meier, Gabriele Messori, Lev Naumov, Thomas Neumann, Piia Post, Gregor Rehder, Anna Rutgersson, and Georg Sebastian Voelker
EGUsphere, https://doi.org/10.5194/egusphere-2025-5496, https://doi.org/10.5194/egusphere-2025-5496, 2025
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This review explains how weather patterns, guided by the polar jet stream, influence the Baltic Sea’s climate and ecosystem. It covers the NAO, blocking events and other processes and discusses how they affect temperature, rainfall, and storms from days to decades. These shifts then impact oxygen levels, productivity, and acidification in the Baltic Sea. Physical links are fairly well known, but biogeochemical pathways remain uncertain.
Pierre Friedlingstein, Michael O'Sullivan, Matthew W. Jones, Robbie M. Andrew, Dorothee C. E. Bakker, Judith Hauck, Peter Landschützer, Corinne Le Quéré, Hongmei Li, Ingrid T. Luijkx, Glen P. Peters, Wouter Peters, Julia Pongratz, Clemens Schwingshackl, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Kjetil Aas, Simone R. Alin, Peter Anthoni, Leticia Barbero, Nicholas R. Bates, Nicolas Bellouin, Alice Benoit-Cattin, Carla F. Berghoff, Raffaele Bernardello, Laurent Bopp, Ida B. M. Brasika, Matthew A. Chamberlain, Naveen Chandra, Frédéric Chevallier, Louise P. Chini, Nathan O. Collier, Thomas H. Colligan, Margot Cronin, Laique Djeutchouang, Xinyu Dou, Matt P. Enright, Kazutaka Enyo, Michael Erb, Wiley Evans, Richard A. Feely, Liang Feng, Daniel J. Ford, Adrianna Foster, Filippa Fransner, Thomas Gasser, Marion Gehlen, Thanos Gkritzalis, Jefferson Goncalves De Souza, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Bertrand Guenet, Özgür Gürses, Kirsty Harrington, Ian Harris, Jens Heinke, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Akihiko Ito, Andrew R. Jacobson, Atul K. Jain, Tereza Jarníková, Annika Jersild, Fei Jiang, Steve D. Jones, Etsushi Kato, Ralph F. Keeling, Kees Klein Goldewijk, Jürgen Knauer, Yawen Kong, Jan Ivar Korsbakken, Charles Koven, Taro Kunimitsu, Xin Lan, Junjie Liu, Zhiqiang Liu, Zhu Liu, Claire Lo Monaco, Lei Ma, Gregg Marland, Patrick C. McGuire, Galen A. McKinley, Joe Melton, Natalie Monacci, Erwan Monier, Eric J. Morgan, David R. Munro, Jens D. Müller, Shin-Ichiro Nakaoka, Lorna R. Nayagam, Yosuke Niwa, Tobias Nutzel, Are Olsen, Abdirahman M. Omar, Naiqing Pan, Sudhanshu Pandey, Denis Pierrot, Zhangcai Qin, Pierre A. G. Regnier, Gregor Rehder, Laure Resplandy, Alizée Roobaert, Thais M. Rosan, Christian Rödenbeck, Jörg Schwinger, Ingunn Skjelvan, T. Luke Smallman, Victoria Spada, Mohanan G. Sreeush, Qing Sun, Adrienne J. Sutton, Colm Sweeney, Didier Swingedouw, Roland Séférian, Shintaro Takao, Hiroaki Tatebe, Hanqin Tian, Xiangjun Tian, Bronte Tilbrook, Hiroyuki Tsujino, Francesco Tubiello, Erik van Ooijen, Guido van der Werf, Sebastiaan J. van de Velde, Anthony Walker, Rik Wanninkhof, Xiaojuan Yang, Wenping Yuan, Xu Yue, and Jiye Zeng
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2025-659, https://doi.org/10.5194/essd-2025-659, 2025
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The Global Carbon Budget 2025 describes the methodology, main results, and datasets used to quantify the anthropogenic emissions of carbon dioxide (CO2) and their partitioning among the atmosphere, land ecosystems, and the ocean over the historical period (1750–2025). These living datasets are updated every year to provide the highest transparency and traceability in the reporting of CO2, the key driver of climate change.
Elizabeth Leon-Palmero, Claudia Frey, Bess B. Ward, Rafael Morales-Baquero, and Isabel Reche
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Reservoirs act as nitrogen sinks and emit nitrous oxide, a potent greenhouse gas and major ozone-depleting substance. We studied two reservoirs and found that nitrification and denitrification produce nitrous oxide in the water column, but denitrification is the main source, fueled by fresh organic matter from phytoplankton. Our results also suggest that nitrous oxide is actively consumed. This study highlights the need to include reservoirs in global nitrous oxide budgets.
Gesa Schulz, Kirstin Dähnke, Tina Sanders, Jan Penopp, Hermann W. Bange, Rena Czeschel, and Birgit Gaye
Biogeosciences, 22, 5943–5959, https://doi.org/10.5194/bg-22-5943-2025, https://doi.org/10.5194/bg-22-5943-2025, 2025
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Oxygen-minimum zones (OMZs) are low-oxygen ocean areas that deplete nitrogen, a key marine nutrient. Understanding nitrogen cycling in OMZs is crucial for the global nitrogen cycle. This study examined nitrogen cycling in the OMZ of the Bay of Bengal and the East Equatorial Indian Ocean, revealing limited mixing between both regions. Surface phytoplankton consumes nitrate, while deeper nitrification recycles nitrogen. In the BoB’s OMZ (100–300 m), nitrogen loss likely occurs via anammox.
Daniel L. Pönisch, Henry C. Bittig, Martin Kolbe, Ingo Schuffenhauer, Stefan Otto, Peter Holtermann, Kusala Premaratne, and Gregor Rehder
Biogeosciences, 22, 3583–3614, https://doi.org/10.5194/bg-22-3583-2025, https://doi.org/10.5194/bg-22-3583-2025, 2025
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Rewetted peatlands exhibit natural spatiotemporal biogeochemical heterogeneity, influenced by water level and vegetation. This study investigated the variability of greenhouse gas distribution in a peatland rewetted with brackish water. Two innovative sensor-equipped platforms were used to measure a wide range of marine physicochemical variables at high temporal resolution. The measurements revealed strong fluctuations in CO2 and CH4, expressed as multi-day, diurnal, and event-based variability.
Johnathan Daniel Maxey, Neil D. Hartstein, Hermann W. Bange, and Moritz Müller
Biogeosciences, 21, 5613–5637, https://doi.org/10.5194/bg-21-5613-2024, https://doi.org/10.5194/bg-21-5613-2024, 2024
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The distribution of N2O in fjord-like estuaries is poorly described in the Southern Hemisphere. Our study describes N2O distribution and its drivers in one such system in Macquarie Harbour, Tasmania. Water samples were collected seasonally in 2022 and 2023. Results show the system removes atmospheric N2O when river flow is high, whereas the system emits N2O when the river flow is low. N2O generated in basins is intercepted by the surface water and exported to the ocean during high river flow.
Silvie Lainela, Erik Jacobs, Stella-Theresa Luik, Gregor Rehder, and Urmas Lips
Biogeosciences, 21, 4495–4519, https://doi.org/10.5194/bg-21-4495-2024, https://doi.org/10.5194/bg-21-4495-2024, 2024
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We evaluate the variability of carbon dioxide and methane in the surface layer of the north-eastern basins of the Baltic Sea in 2018. We show that the shallower coastal areas have considerably higher spatial variability and seasonal amplitude of surface layer pCO2 and cCH4 than measured in the offshore areas of the Baltic Sea. Despite this high variability, caused mostly by coastal physical processes, the average annual air–sea CO2 fluxes differed only marginally between the sub-basins.
Riel Carlo O. Ingeniero, Gesa Schulz, and Hermann W. Bange
Biogeosciences, 21, 3425–3440, https://doi.org/10.5194/bg-21-3425-2024, https://doi.org/10.5194/bg-21-3425-2024, 2024
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Our research is the first to measure dissolved NO concentrations in temperate estuarine waters, providing insights into its distribution under varying conditions and enhancing our understanding of its production processes. Dissolved NO was supersaturated in the Elbe Estuary, indicating that it is a source of atmospheric NO. The observed distribution of dissolved NO most likely resulted from nitrification.
Colette L. Kelly, Nicole M. Travis, Pascale Anabelle Baya, Claudia Frey, Xin Sun, Bess B. Ward, and Karen L. Casciotti
Biogeosciences, 21, 3215–3238, https://doi.org/10.5194/bg-21-3215-2024, https://doi.org/10.5194/bg-21-3215-2024, 2024
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Nitrous oxide, a potent greenhouse gas, accumulates in regions of the ocean that are low in dissolved oxygen. We used a novel combination of chemical tracers to determine how nitrous oxide is produced in one of these regions, the eastern tropical North Pacific Ocean. Our experiments showed that the two most important sources of nitrous oxide under low-oxygen conditions are denitrification, an anaerobic process, and a novel “hybrid” process performed by ammonia-oxidizing archaea.
Hanqin Tian, Naiqing Pan, Rona L. Thompson, Josep G. Canadell, Parvadha Suntharalingam, Pierre Regnier, Eric A. Davidson, Michael Prather, Philippe Ciais, Marilena Muntean, Shufen Pan, Wilfried Winiwarter, Sönke Zaehle, Feng Zhou, Robert B. Jackson, Hermann W. Bange, Sarah Berthet, Zihao Bian, Daniele Bianchi, Alexander F. Bouwman, Erik T. Buitenhuis, Geoffrey Dutton, Minpeng Hu, Akihiko Ito, Atul K. Jain, Aurich Jeltsch-Thömmes, Fortunat Joos, Sian Kou-Giesbrecht, Paul B. Krummel, Xin Lan, Angela Landolfi, Ronny Lauerwald, Ya Li, Chaoqun Lu, Taylor Maavara, Manfredi Manizza, Dylan B. Millet, Jens Mühle, Prabir K. Patra, Glen P. Peters, Xiaoyu Qin, Peter Raymond, Laure Resplandy, Judith A. Rosentreter, Hao Shi, Qing Sun, Daniele Tonina, Francesco N. Tubiello, Guido R. van der Werf, Nicolas Vuichard, Junjie Wang, Kelley C. Wells, Luke M. Western, Chris Wilson, Jia Yang, Yuanzhi Yao, Yongfa You, and Qing Zhu
Earth Syst. Sci. Data, 16, 2543–2604, https://doi.org/10.5194/essd-16-2543-2024, https://doi.org/10.5194/essd-16-2543-2024, 2024
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Atmospheric concentrations of nitrous oxide (N2O), a greenhouse gas 273 times more potent than carbon dioxide, have increased by 25 % since the preindustrial period, with the highest observed growth rate in 2020 and 2021. This rapid growth rate has primarily been due to a 40 % increase in anthropogenic emissions since 1980. Observed atmospheric N2O concentrations in recent years have exceeded the worst-case climate scenario, underscoring the importance of reducing anthropogenic N2O emissions.
Henry C. Bittig, Erik Jacobs, Thomas Neumann, and Gregor Rehder
Earth Syst. Sci. Data, 16, 753–773, https://doi.org/10.5194/essd-16-753-2024, https://doi.org/10.5194/essd-16-753-2024, 2024
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We present a pCO2 climatology of the Baltic Sea using a new approach to extrapolate from individual observations to the entire Baltic Sea. The extrapolation approach uses (a) a model to inform on how data at one location are connected to data at other locations, together with (b) very accurate pCO2 observations from 2003 to 2021 as the base data. The climatology can be used e.g. to assess uptake and release of CO2 or to identify extreme events.
Pierre Friedlingstein, Michael O'Sullivan, Matthew W. Jones, Robbie M. Andrew, Dorothee C. E. Bakker, Judith Hauck, Peter Landschützer, Corinne Le Quéré, Ingrid T. Luijkx, Glen P. Peters, Wouter Peters, Julia Pongratz, Clemens Schwingshackl, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Robert B. Jackson, Simone R. Alin, Peter Anthoni, Leticia Barbero, Nicholas R. Bates, Meike Becker, Nicolas Bellouin, Bertrand Decharme, Laurent Bopp, Ida Bagus Mandhara Brasika, Patricia Cadule, Matthew A. Chamberlain, Naveen Chandra, Thi-Tuyet-Trang Chau, Frédéric Chevallier, Louise P. Chini, Margot Cronin, Xinyu Dou, Kazutaka Enyo, Wiley Evans, Stefanie Falk, Richard A. Feely, Liang Feng, Daniel J. Ford, Thomas Gasser, Josefine Ghattas, Thanos Gkritzalis, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Özgür Gürses, Ian Harris, Matthew Hefner, Jens Heinke, Richard A. Houghton, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Andrew R. Jacobson, Atul Jain, Tereza Jarníková, Annika Jersild, Fei Jiang, Zhe Jin, Fortunat Joos, Etsushi Kato, Ralph F. Keeling, Daniel Kennedy, Kees Klein Goldewijk, Jürgen Knauer, Jan Ivar Korsbakken, Arne Körtzinger, Xin Lan, Nathalie Lefèvre, Hongmei Li, Junjie Liu, Zhiqiang Liu, Lei Ma, Greg Marland, Nicolas Mayot, Patrick C. McGuire, Galen A. McKinley, Gesa Meyer, Eric J. Morgan, David R. Munro, Shin-Ichiro Nakaoka, Yosuke Niwa, Kevin M. O'Brien, Are Olsen, Abdirahman M. Omar, Tsuneo Ono, Melf Paulsen, Denis Pierrot, Katie Pocock, Benjamin Poulter, Carter M. Powis, Gregor Rehder, Laure Resplandy, Eddy Robertson, Christian Rödenbeck, Thais M. Rosan, Jörg Schwinger, Roland Séférian, T. Luke Smallman, Stephen M. Smith, Reinel Sospedra-Alfonso, Qing Sun, Adrienne J. Sutton, Colm Sweeney, Shintaro Takao, Pieter P. Tans, Hanqin Tian, Bronte Tilbrook, Hiroyuki Tsujino, Francesco Tubiello, Guido R. van der Werf, Erik van Ooijen, Rik Wanninkhof, Michio Watanabe, Cathy Wimart-Rousseau, Dongxu Yang, Xiaojuan Yang, Wenping Yuan, Xu Yue, Sönke Zaehle, Jiye Zeng, and Bo Zheng
Earth Syst. Sci. Data, 15, 5301–5369, https://doi.org/10.5194/essd-15-5301-2023, https://doi.org/10.5194/essd-15-5301-2023, 2023
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The Global Carbon Budget 2023 describes the methodology, main results, and data sets used to quantify the anthropogenic emissions of carbon dioxide (CO2) and their partitioning among the atmosphere, land ecosystems, and the ocean over the historical period (1750–2023). These living datasets are updated every year to provide the highest transparency and traceability in the reporting of CO2, the key driver of climate change.
Weiyi Tang, Bess B. Ward, Michael Beman, Laura Bristow, Darren Clark, Sarah Fawcett, Claudia Frey, François Fripiat, Gerhard J. Herndl, Mhlangabezi Mdutyana, Fabien Paulot, Xuefeng Peng, Alyson E. Santoro, Takuhei Shiozaki, Eva Sintes, Charles Stock, Xin Sun, Xianhui S. Wan, Min N. Xu, and Yao Zhang
Earth Syst. Sci. Data, 15, 5039–5077, https://doi.org/10.5194/essd-15-5039-2023, https://doi.org/10.5194/essd-15-5039-2023, 2023
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Nitrification and nitrifiers play an important role in marine nitrogen and carbon cycles by converting ammonium to nitrite and nitrate. Nitrification could affect microbial community structure, marine productivity, and the production of nitrous oxide – a powerful greenhouse gas. We introduce the newly constructed database of nitrification and nitrifiers in the marine water column and guide future research efforts in field observations and model development of nitrification.
Gesa Schulz, Tina Sanders, Yoana G. Voynova, Hermann W. Bange, and Kirstin Dähnke
Biogeosciences, 20, 3229–3247, https://doi.org/10.5194/bg-20-3229-2023, https://doi.org/10.5194/bg-20-3229-2023, 2023
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Nitrous oxide (N2O) is an important greenhouse gas. However, N2O emissions from estuaries underlie significant uncertainties due to limited data availability and high spatiotemporal variability. We found the Elbe Estuary (Germany) to be a year-round source of N2O, with the highest emissions in winter along with high nitrogen loads. However, in spring and summer, N2O emissions did not decrease alongside lower nitrogen loads because organic matter fueled in situ N2O production along the estuary.
John C. Tracey, Andrew R. Babbin, Elizabeth Wallace, Xin Sun, Katherine L. DuRussel, Claudia Frey, Donald E. Martocello III, Tyler Tamasi, Sergey Oleynik, and Bess B. Ward
Biogeosciences, 20, 2499–2523, https://doi.org/10.5194/bg-20-2499-2023, https://doi.org/10.5194/bg-20-2499-2023, 2023
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Nitrogen (N) is essential for life; thus, its availability plays a key role in determining marine productivity. Using incubations of seawater spiked with a rare form of N measurable on a mass spectrometer, we quantified microbial pathways that determine marine N availability. The results show that pathways that recycle N have higher rates than those that result in its loss from biomass and present new evidence for anaerobic nitrite oxidation, a process long thought to be strictly aerobic.
Guanlin Li, Damian L. Arévalo-Martínez, Riel Carlo O. Ingeniero, and Hermann W. Bange
EGUsphere, https://doi.org/10.5194/egusphere-2023-771, https://doi.org/10.5194/egusphere-2023-771, 2023
Preprint archived
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Dissolved carbon monoxide (CO) surface concentrations were first measured at 14 stations in the Ria Formosa Lagoon system in May 2021. Ria Formosa was a source of atmospheric CO. Microbial consumption accounted for 83 % of the CO production. The results of a 48-hour irradiation experiment with aquaculture effluent water indicated that aquaculture facilities in the Ria Formosa Lagoon seem to be a negligible source of atmospheric CO.
Hanna I. Campen, Damian L. Arévalo-Martínez, and Hermann W. Bange
Biogeosciences, 20, 1371–1379, https://doi.org/10.5194/bg-20-1371-2023, https://doi.org/10.5194/bg-20-1371-2023, 2023
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Carbon monoxide (CO) is a climate-relevant trace gas emitted from the ocean. However, oceanic CO cycling is understudied. Results from incubation experiments conducted in the Fram Strait (Arctic Ocean) indicated that (i) pH did not affect CO cycling and (ii) enhanced CO production and consumption were positively correlated with coloured dissolved organic matter and nitrate concentrations. This suggests microbial CO uptake to be the driving factor for CO cycling in the Arctic Ocean.
Damian L. Arévalo-Martínez, Amir Haroon, Hermann W. Bange, Ercan Erkul, Marion Jegen, Nils Moosdorf, Jens Schneider von Deimling, Christian Berndt, Michael Ernst Böttcher, Jasper Hoffmann, Volker Liebetrau, Ulf Mallast, Gudrun Massmann, Aaron Micallef, Holly A. Michael, Hendrik Paasche, Wolfgang Rabbel, Isaac Santos, Jan Scholten, Katrin Schwalenberg, Beata Szymczycha, Ariel T. Thomas, Joonas J. Virtasalo, Hannelore Waska, and Bradley A. Weymer
Biogeosciences, 20, 647–662, https://doi.org/10.5194/bg-20-647-2023, https://doi.org/10.5194/bg-20-647-2023, 2023
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Groundwater flows at the land–ocean transition and the extent of freshened groundwater below the seafloor are increasingly relevant in marine sciences, both because they are a highly uncertain term of biogeochemical budgets and due to the emerging interest in the latter as a resource. Here, we discuss our perspectives on future research directions to better understand land–ocean connectivity through groundwater and its potential responses to natural and human-induced environmental changes.
Daniel L. Pönisch, Anne Breznikar, Cordula N. Gutekunst, Gerald Jurasinski, Maren Voss, and Gregor Rehder
Biogeosciences, 20, 295–323, https://doi.org/10.5194/bg-20-295-2023, https://doi.org/10.5194/bg-20-295-2023, 2023
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Peatland rewetting is known to reduce dissolved nutrients and greenhouse gases; however, short-term nutrient leaching and high CH4 emissions shortly after rewetting are likely to occur. We investigated the rewetting of a coastal peatland with brackish water and its effects on nutrient release and greenhouse gas fluxes. Nutrient concentrations were higher in the peatland than in the adjacent bay, leading to an export. CH4 emissions did not increase, which is in contrast to freshwater rewetting.
Thomas Neumann, Hagen Radtke, Bronwyn Cahill, Martin Schmidt, and Gregor Rehder
Geosci. Model Dev., 15, 8473–8540, https://doi.org/10.5194/gmd-15-8473-2022, https://doi.org/10.5194/gmd-15-8473-2022, 2022
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Marine ecosystem models are usually constrained by the elements nitrogen and phosphorus and consider carbon in organic matter in a fixed ratio. Recent observations show a substantial deviation from the simulated carbon cycle variables. In this study, we present a marine ecosystem model for the Baltic Sea which allows for a flexible uptake ratio for carbon, nitrogen, and phosphorus. With this extension, the model reflects much more reasonable variables of the marine carbon cycle.
Sonja Gindorf, Hermann W. Bange, Dennis Booge, and Annette Kock
Biogeosciences, 19, 4993–5006, https://doi.org/10.5194/bg-19-4993-2022, https://doi.org/10.5194/bg-19-4993-2022, 2022
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Methane is a climate-relevant greenhouse gas which is emitted to the atmosphere from coastal areas such as the Baltic Sea. We measured the methane concentration in the water column of the western Kiel Bight. Methane concentrations were higher in September than in June. We found no relationship between the 2018 European heatwave and methane concentrations. Our results show that the methane distribution in the water column is strongly affected by temporal and spatial variabilities.
Pierre Friedlingstein, Matthew W. Jones, Michael O'Sullivan, Robbie M. Andrew, Dorothee C. E. Bakker, Judith Hauck, Corinne Le Quéré, Glen P. Peters, Wouter Peters, Julia Pongratz, Stephen Sitch, Josep G. Canadell, Philippe Ciais, Rob B. Jackson, Simone R. Alin, Peter Anthoni, Nicholas R. Bates, Meike Becker, Nicolas Bellouin, Laurent Bopp, Thi Tuyet Trang Chau, Frédéric Chevallier, Louise P. Chini, Margot Cronin, Kim I. Currie, Bertrand Decharme, Laique M. Djeutchouang, Xinyu Dou, Wiley Evans, Richard A. Feely, Liang Feng, Thomas Gasser, Dennis Gilfillan, Thanos Gkritzalis, Giacomo Grassi, Luke Gregor, Nicolas Gruber, Özgür Gürses, Ian Harris, Richard A. Houghton, George C. Hurtt, Yosuke Iida, Tatiana Ilyina, Ingrid T. Luijkx, Atul Jain, Steve D. Jones, Etsushi Kato, Daniel Kennedy, Kees Klein Goldewijk, Jürgen Knauer, Jan Ivar Korsbakken, Arne Körtzinger, Peter Landschützer, Siv K. Lauvset, Nathalie Lefèvre, Sebastian Lienert, Junjie Liu, Gregg Marland, Patrick C. McGuire, Joe R. Melton, David R. Munro, Julia E. M. S. Nabel, Shin-Ichiro Nakaoka, Yosuke Niwa, Tsuneo Ono, Denis Pierrot, Benjamin Poulter, Gregor Rehder, Laure Resplandy, Eddy Robertson, Christian Rödenbeck, Thais M. Rosan, Jörg Schwinger, Clemens Schwingshackl, Roland Séférian, Adrienne J. Sutton, Colm Sweeney, Toste Tanhua, Pieter P. Tans, Hanqin Tian, Bronte Tilbrook, Francesco Tubiello, Guido R. van der Werf, Nicolas Vuichard, Chisato Wada, Rik Wanninkhof, Andrew J. Watson, David Willis, Andrew J. Wiltshire, Wenping Yuan, Chao Yue, Xu Yue, Sönke Zaehle, and Jiye Zeng
Earth Syst. Sci. Data, 14, 1917–2005, https://doi.org/10.5194/essd-14-1917-2022, https://doi.org/10.5194/essd-14-1917-2022, 2022
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The Global Carbon Budget 2021 describes the data sets and methodology used to quantify the emissions of carbon dioxide and their partitioning among the atmosphere, land, and ocean. These living data are updated every year to provide the highest transparency and traceability in the reporting of CO2, the key driver of climate change.
Karol Kuliński, Gregor Rehder, Eero Asmala, Alena Bartosova, Jacob Carstensen, Bo Gustafsson, Per O. J. Hall, Christoph Humborg, Tom Jilbert, Klaus Jürgens, H. E. Markus Meier, Bärbel Müller-Karulis, Michael Naumann, Jørgen E. Olesen, Oleg Savchuk, Andreas Schramm, Caroline P. Slomp, Mikhail Sofiev, Anna Sobek, Beata Szymczycha, and Emma Undeman
Earth Syst. Dynam., 13, 633–685, https://doi.org/10.5194/esd-13-633-2022, https://doi.org/10.5194/esd-13-633-2022, 2022
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The paper covers the aspects related to changes in carbon, nitrogen, and phosphorus (C, N, P) external loads; their transformations in the coastal zone; changes in organic matter production (eutrophication) and remineralization (oxygen availability); and the role of sediments in burial and turnover of C, N, and P. Furthermore, this paper also focuses on changes in the marine CO2 system, the structure of the microbial community, and the role of contaminants for biogeochemical processes.
Yanan Zhao, Dennis Booge, Christa A. Marandino, Cathleen Schlundt, Astrid Bracher, Elliot L. Atlas, Jonathan Williams, and Hermann W. Bange
Biogeosciences, 19, 701–714, https://doi.org/10.5194/bg-19-701-2022, https://doi.org/10.5194/bg-19-701-2022, 2022
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We present here, for the first time, simultaneously measured dimethylsulfide (DMS) seawater concentrations and DMS atmospheric mole fractions from the Peruvian upwelling region during two cruises in December 2012 and October 2015. Our results indicate low oceanic DMS concentrations and atmospheric DMS molar fractions in surface waters and the atmosphere, respectively. In addition, the Peruvian upwelling region was identified as an insignificant source of DMS emissions during both periods.
Wangwang Ye, Hermann W. Bange, Damian L. Arévalo-Martínez, Hailun He, Yuhong Li, Jianwen Wen, Jiexia Zhang, Jian Liu, Man Wu, and Liyang Zhan
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-334, https://doi.org/10.5194/bg-2021-334, 2022
Manuscript not accepted for further review
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CH4 is the second important greenhouse gas after CO2. We show that CH4 consumption and sea-ice melting influence the CH4 distribution in the Ross Sea (Southern Ocean), causing undersaturation and net uptake of CH4 during summertime. This study confirms the capability of surface water in the high-latitude Southern Ocean regions to take up atmospheric CH4 which, in turn, will help to improve predictions of how CH4 release/uptake from the ocean will develop when sea-ice retreats in the future.
Martti Honkanen, Jens Daniel Müller, Jukka Seppälä, Gregor Rehder, Sami Kielosto, Pasi Ylöstalo, Timo Mäkelä, Juha Hatakka, and Lauri Laakso
Ocean Sci., 17, 1657–1675, https://doi.org/10.5194/os-17-1657-2021, https://doi.org/10.5194/os-17-1657-2021, 2021
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The exchange of carbon dioxide (CO2) between the sea and the atmosphere is regulated by the gradient of CO2 partial pressure (pCO2) between the sea and the air. The daily variation of the seawater pCO2 recorded at the fixed station Utö in the Baltic Sea was found to be mainly biologically driven. Calculation of the annual net exchange of CO2 between the sea and atmosphere based on daily measurements of pCO2 carried out using the same sampling time every day could introduce a bias of up to 12 %.
Jens Daniel Müller, Bernd Schneider, Ulf Gräwe, Peer Fietzek, Marcus Bo Wallin, Anna Rutgersson, Norbert Wasmund, Siegfried Krüger, and Gregor Rehder
Biogeosciences, 18, 4889–4917, https://doi.org/10.5194/bg-18-4889-2021, https://doi.org/10.5194/bg-18-4889-2021, 2021
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Based on profiling pCO2 measurements from a field campaign, we quantify the biomass production of a cyanobacteria bloom in the Baltic Sea, the export of which would foster deep water deoxygenation. We further demonstrate how this biomass production can be accurately reconstructed from long-term surface measurements made on cargo vessels in combination with modelled temperature profiles. This approach enables a better understanding of a severe concern for the Baltic’s good environmental status.
Erik Jacobs, Henry C. Bittig, Ulf Gräwe, Carolyn A. Graves, Michael Glockzin, Jens D. Müller, Bernd Schneider, and Gregor Rehder
Biogeosciences, 18, 2679–2709, https://doi.org/10.5194/bg-18-2679-2021, https://doi.org/10.5194/bg-18-2679-2021, 2021
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We use a unique data set of 8 years of continuous carbon dioxide (CO2) and methane (CH4) surface water measurements from a commercial ferry to study upwelling in the Baltic Sea. Its seasonality and regional and interannual variability are examined. Strong upwelling events drastically increase local surface CO2 and CH4 levels and are mostly detected in late summer after long periods of impaired mixing. We introduce an extrapolation method to estimate regional upwelling-induced trace gas fluxes.
Trystan Sanders, Jörn Thomsen, Jens Daniel Müller, Gregor Rehder, and Frank Melzner
Biogeosciences, 18, 2573–2590, https://doi.org/10.5194/bg-18-2573-2021, https://doi.org/10.5194/bg-18-2573-2021, 2021
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The Baltic Sea is expected to experience a rapid drop in salinity and increases in acidity and warming in the next century. Calcifying mussels dominate Baltic Sea seafloor ecosystems yet are sensitive to changes in seawater chemistry. We combine laboratory experiments and a field study and show that a lack of calcium causes extremely slow growth rates in mussels at low salinities. Subsequently, climate change in the Baltic may have drastic ramifications for Baltic seafloor ecosystems.
Yanan Zhao, Cathleen Schlundt, Dennis Booge, and Hermann W. Bange
Biogeosciences, 18, 2161–2179, https://doi.org/10.5194/bg-18-2161-2021, https://doi.org/10.5194/bg-18-2161-2021, 2021
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We present a unique and comprehensive time-series study of biogenic sulfur compounds in the southwestern Baltic Sea, from 2009 to 2018. Dimethyl sulfide is one of the key players regulating global climate change, as well as dimethylsulfoniopropionate and dimethyl sulfoxide. Their decadal trends did not follow increasing temperature but followed some algae group abundances at the Boknis Eck Time Series Station.
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Short summary
Nitrous oxide (N2O), a potent greenhouse gas, is released from coastal seas & estuaries, yet we don't fully understand how it is formed and consumed. In this study we collected water from several sites in the central Baltic Sea. N2O came from ammonia in oxic waters. Deep waters with low to no oxygen noted more active N2O cycling. The seafloor was a source in some areas. Typically N2O is produced by bacteria, but our results indicate possibility of other players like fungi or chemical reactions.
Nitrous oxide (N2O), a potent greenhouse gas, is released from coastal seas & estuaries, yet we...
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