Articles | Volume 23, issue 1
https://doi.org/10.5194/bg-23-1-2026
© 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-23-1-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
05 Jan 2026
Research article |
| 05 Jan 2026
| 05 Jan 2026
Nitrogen fixation in Arctic coastal waters (Qeqertarsuaq, West Greenland): influence of glacial melt on diazotrophs, nutrient availability, and seasonal blooms
Isabell Schlangen
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Elizabeth Leon-Palmero
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Department of Geosciences, Princeton University, Princeton, New Jersey
Annabell Moser
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Peihang Xu
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Erik Laursen
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
Carolin R. Löscher
CORRESPONDING AUTHOR
Nordcee, Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
DIAS, University of Southern Denmark, Odense, Denmark
Related authors
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Elizabeth Leon-Palmero, Claudia Frey, Bess B. Ward, Rafael Morales-Baquero, and Isabel Reche
EGUsphere, https://doi.org/10.5194/egusphere-2025-5003, https://doi.org/10.5194/egusphere-2025-5003, 2025
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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.
Anna Pedersen, Carolin R. Löscher, and Steffen M. Olsen
Biogeosciences, 22, 5009–5029, https://doi.org/10.5194/bg-22-5009-2025, https://doi.org/10.5194/bg-22-5009-2025, 2025
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The North Atlantic plays a crucial role in absorbing atmospheric CO2, but its air–sea CO2 flux varies across time and space. Using historical climate model simulations, we investigate how physical and oceanic processes drive the variability. Our results show that sea ice, temperature, salinity, wind stress, and ocean circulation shape CO2 exchange, with short-term fluctuations playing a dominant role. Understanding these complex interactions is key to predicting future ocean carbon uptake.
Sebastian I. Cantarero, Edgart Flores, Harry Allbrook, Paulina Aguayo, Cristian A. Vargas, John E. Tamanaha, J. Bentley C. Scholz, Lennart T. Bach, Carolin R. Löscher, Ulf Riebesell, Balaji Rajagopalan, Nadia Dildar, and Julio Sepúlveda
Biogeosciences, 21, 3927–3958, https://doi.org/10.5194/bg-21-3927-2024, https://doi.org/10.5194/bg-21-3927-2024, 2024
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Our study explores lipid remodeling in response to environmental stress, specifically how cell membrane chemistry changes. We focus on intact polar lipids in a phytoplankton community exposed to diverse stressors in a mesocosm experiment. The observed remodeling indicates acyl chain recycling for energy storage in intact polar lipids during stress, reallocating resources based on varying growth conditions. This understanding is essential to grasp the system's impact on cellular pools.
Jakob Rønning, Zarah J. Kofoed, Mats Jacobsen, and Carolin R. Löscher
EGUsphere, https://doi.org/10.5194/egusphere-2023-2884, https://doi.org/10.5194/egusphere-2023-2884, 2024
Preprint archived
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In our study, we assessed the impact of olivine on marine primary producers of ocean-based solutions. The experiments revealed no negative effects on carbon fixation rates. Additions of the alkaline minerals did not establish growth inhibition; instead, they showed slight growth increases with species-specific responses. Ni exposure from olivine did not inhibit growth. However, limitations include the absence of responses in natural settings.
Matthew D. Eisaman, Sonja Geilert, Phil Renforth, Laura Bastianini, James Campbell, Andrew W. Dale, Spyros Foteinis, Patricia Grasse, Olivia Hawrot, Carolin R. Löscher, Greg H. Rau, and Jakob Rønning
State Planet, 2-oae2023, 3, https://doi.org/10.5194/sp-2-oae2023-3-2023, https://doi.org/10.5194/sp-2-oae2023-3-2023, 2023
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Ocean-alkalinity-enhancement technologies refer to various methods and approaches aimed at increasing the alkalinity of seawater. This chapter explores technologies for increasing ocean alkalinity, including electrochemical-based approaches, ocean liming, accelerated weathering of limestone, hydrated carbonate addition, and coastal enhanced weathering, and suggests best practices in research and development.
Zhibo Shao, Yangchun Xu, Hua Wang, Weicheng Luo, Lice Wang, Yuhong Huang, Nona Sheila R. Agawin, Ayaz Ahmed, Mar Benavides, Mikkel Bentzon-Tilia, Ilana Berman-Frank, Hugo Berthelot, Isabelle C. Biegala, Mariana B. Bif, Antonio Bode, Sophie Bonnet, Deborah A. Bronk, Mark V. Brown, Lisa Campbell, Douglas G. Capone, Edward J. Carpenter, Nicolas Cassar, Bonnie X. Chang, Dreux Chappell, Yuh-ling Lee Chen, Matthew J. Church, Francisco M. Cornejo-Castillo, Amália Maria Sacilotto Detoni, Scott C. Doney, Cecile Dupouy, Marta Estrada, Camila Fernandez, Bieito Fernández-Castro, Debany Fonseca-Batista, Rachel A. Foster, Ken Furuya, Nicole Garcia, Kanji Goto, Jesús Gago, Mary R. Gradoville, M. Robert Hamersley, Britt A. Henke, Cora Hörstmann, Amal Jayakumar, Zhibing Jiang, Shuh-Ji Kao, David M. Karl, Leila R. Kittu, Angela N. Knapp, Sanjeev Kumar, Julie LaRoche, Hongbin Liu, Jiaxing Liu, Caroline Lory, Carolin R. Löscher, Emilio Marañón, Lauren F. Messer, Matthew M. Mills, Wiebke Mohr, Pia H. Moisander, Claire Mahaffey, Robert Moore, Beatriz Mouriño-Carballido, Margaret R. Mulholland, Shin-ichiro Nakaoka, Joseph A. Needoba, Eric J. Raes, Eyal Rahav, Teodoro Ramírez-Cárdenas, Christian Furbo Reeder, Lasse Riemann, Virginie Riou, Julie C. Robidart, Vedula V. S. S. Sarma, Takuya Sato, Himanshu Saxena, Corday Selden, Justin R. Seymour, Dalin Shi, Takuhei Shiozaki, Arvind Singh, Rachel E. Sipler, Jun Sun, Koji Suzuki, Kazutaka Takahashi, Yehui Tan, Weiyi Tang, Jean-Éric Tremblay, Kendra Turk-Kubo, Zuozhu Wen, Angelicque E. White, Samuel T. Wilson, Takashi Yoshida, Jonathan P. Zehr, Run Zhang, Yao Zhang, and Ya-Wei Luo
Earth Syst. Sci. Data, 15, 3673–3709, https://doi.org/10.5194/essd-15-3673-2023, https://doi.org/10.5194/essd-15-3673-2023, 2023
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N2 fixation by marine diazotrophs is an important bioavailable N source to the global ocean. This updated global oceanic diazotroph database increases the number of in situ measurements of N2 fixation rates, diazotrophic cell abundances, and nifH gene copy abundances by 184 %, 86 %, and 809 %, respectively. Using the updated database, the global marine N2 fixation rate is estimated at 223 ± 30 Tg N yr−1, which triplicates that using the original database.
Christian Furbo Reeder, Ina Stoltenberg, Jamileh Javidpour, and Carolin Regina Löscher
Ocean Sci., 18, 401–417, https://doi.org/10.5194/os-18-401-2022, https://doi.org/10.5194/os-18-401-2022, 2022
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The Baltic Sea is predicted to freshen in the future. To explore the effect of decreasing salinity on N2 fixers, we followed the natural salinity gradient in the Baltic Sea from the Kiel Fjord to the Gotland Basin and identified an N2 fixer community dominated by Nodularia and UCYN-A. A salinity threshold was identified at a salinity of 10, with Nodularia dominating at low and UCYN-A dominating at higher salinity, suggesting a future expansion of Nodularia N2 fixers and a retraction of UCYN-A.
Carolin R. Löscher
Biogeosciences, 18, 4953–4963, https://doi.org/10.5194/bg-18-4953-2021, https://doi.org/10.5194/bg-18-4953-2021, 2021
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The Bay of Bengal (BoB) is classically seen as an ocean region with low primary production, which has been predicted to decrease even further. Here, the importance of such a trend is used to explore what could happen to the BoB's low-oxygen core waters if primary production decreases. Lower biological production leads to less oxygen loss in deeper waters by respiration; thus it could be that oxygen will not further decrease and the BoB will not become anoxic, different to other low-oxygen areas.
Kai G. Schulz, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Isabel Baños, Tim Boxhammer, Dirk Erler, Maricarmen Igarza, Verena Kalter, Andrea Ludwig, Carolin Löscher, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Elisabeth von der Esch, Bess B. Ward, and Ulf Riebesell
Biogeosciences, 18, 4305–4320, https://doi.org/10.5194/bg-18-4305-2021, https://doi.org/10.5194/bg-18-4305-2021, 2021
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Upwelling of nutrient-rich deep waters to the surface make eastern boundary upwelling systems hot spots of marine productivity. This leads to subsurface oxygen depletion and the transformation of bioavailable nitrogen into inert N2. Here we quantify nitrogen loss processes following a simulated deep water upwelling. Denitrification was the dominant process, and budget calculations suggest that a significant portion of nitrogen that could be exported to depth is already lost in the surface ocean.
Siqi Wu, Moge Du, Xianhui Sean Wan, Corday Selden, Mar Benavides, Sophie Bonnet, Robert Hamersley, Carolin R. Löscher, Margaret R. Mulholland, Xiuli Yan, and Shuh-Ji Kao
Biogeosciences Discuss., https://doi.org/10.5194/bg-2021-104, https://doi.org/10.5194/bg-2021-104, 2021
Preprint withdrawn
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Nitrogen (N2) fixation is one of the most important nutrient sources to the ocean. Here, we report N2 fixation in the deep, dark ocean in the South China Sea via a highly sensitive new method and elaborate controls, showing the overlooked importance of N2 fixation in the deep ocean. By global data compilation, we also provide an easy measured basic parameter to estimate deep N2 fixation. Our study may help to expand the area limit of N2 fixation studies and better constrain global N2 fixation.
Gerd Krahmann, Damian L. Arévalo-Martínez, Andrew W. Dale, Marcus Dengler, Anja Engel, Nicolaas Glock, Patricia Grasse, Johannes Hahn, Helena Hauss, Mark Hopwood, Rainer Kiko, Alexandra Loginova, Carolin R. Löscher, Marie Maßmig, Alexandra-Sophie Roy, Renato Salvatteci, Stefan Sommer, Toste Tanhua, and Hela Mehrtens
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2020-308, https://doi.org/10.5194/essd-2020-308, 2021
Preprint withdrawn
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The project "Climate-Biogeochemistry Interactions in the Tropical Ocean" (SFB 754) was a multidisciplinary research project active from 2008 to 2019 aimed at a better understanding of the coupling between the tropical climate and ocean circulation and the ocean's oxygen and nutrient balance. On 34 research cruises, mainly in the Southeast Tropical Pacific and the Northeast Tropical Atlantic, 1071 physical, chemical and biological data sets were collected.
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Short summary
We explored nitrogen fixation in the Arctic Ocean, revealing its key role in supporting coastal productivity, especially near melting glaciers. By combining molecular data, rate measurements, and environmental analysis, we identified dominant microbes like symbiotic unicellular cyanobacteria and linked high nitrogen fixation to glacial melt. Our findings suggest that climate-driven changes may expand niches for these microbes, reshaping nitrogen cycles and Arctic productivity in the future.
We explored nitrogen fixation in the Arctic Ocean, revealing its key role in supporting coastal...
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