Articles | Volume 22, issue 12
https://doi.org/10.5194/bg-22-2749-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Special issue:
https://doi.org/10.5194/bg-22-2749-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
18 Jun 2025
Research article |
| 18 Jun 2025
| 18 Jun 2025
Ocean alkalinity enhancement in an open-ocean ecosystem: biogeochemical responses and carbon storage durability
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
Mathias Haunost
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
Silvan Urs Goldenberg
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
Jens Hartmann
Institute for Geology, University of Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany
Nicolás Sánchez
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
Julieta Schneider
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
Niels Suitner
Institute for Geology, University of Hamburg, Bundesstrasse 55, 20146 Hamburg, Germany
Ulf Riebesell
Biological Oceanography, GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
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Ocean alkalinity enhancement (OAE) is being evaluated for its capacity to absorb atmospheric CO2 in the ocean and store it long term to mitigate climate change. As researchers plan for field tests to gain insights into OAE, sharing knowledge on its environmental impact on marine ecosystems is urgent. Our study examined NaOH-induced OAE in Emiliania huxleyi, a key coccolithophore species, and found that the added total alkalinity (ΔTA) should stay below 600 µmol kg⁻¹ to avoid negative impacts.
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The sinking velocity of marine particles affects how much atmospheric CO2 is stored inside our oceans. We measured particle sinking velocities in the Peruvian upwelling system and assessed their physical and biochemical drivers. We found that sinking velocity was mainly influenced by particle size and porosity, while ballasting minerals played only a minor role. Our findings help us to better understand the particle sinking dynamics in this highly productive marine system.
Allanah Joy Paul, Lennart Thomas Bach, Javier Arístegui, Elisabeth von der Esch, Nauzet Hernández-Hernández, Jonna Piiparinen, Laura Ramajo, Kristian Spilling, and Ulf Riebesell
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We investigated how different deep water chemistry and biology modulate the response of surface phytoplankton communities to upwelling in the Peruvian coastal zone. Our results show that the most influential drivers were the ratio of inorganic nutrients (N : P) and the microbial community present in upwelling source water. These led to unexpected and variable development in the phytoplankton assemblage that could not be predicted by the amount of inorganic nutrients alone.
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The eastern boundary upwelling system off Peru is among Earth's most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.
Anu Vehmaa, Anna-Karin Almén, Andreas Brutemark, Allanah Paul, Ulf Riebesell, Sara Furuhagen, and Jonna Engström-Öst
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Ocean acidification is challenging phenotypic plasticity of individuals and populations. We studied phenotypic plasticity of the calanoid copepod Acartia bifilosa in the course of a pelagic, large-volume mesocosm study in the Baltic Sea. We found significant negative effects of ocean acidification on adult female copepod size and egg hatching success. Overall, these results indicate that A. bifilosa could be affected by projected near-future CO2 levels.
Kristian Spilling, Kai G. Schulz, Allanah J. Paul, Tim Boxhammer, Eric P. Achterberg, Thomas Hornick, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Kate Crawfurd, Corina P. D. Brussaard, Hans-Peter Grossart, and Ulf Riebesell
Biogeosciences, 13, 6081–6093, https://doi.org/10.5194/bg-13-6081-2016, https://doi.org/10.5194/bg-13-6081-2016, 2016
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We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO2 levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO2 levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO2 environment, and not by increased photosynthetic fixation of CO2. Our carbon budget can be used to better disentangle the effects of ocean acidification.
Kristian Spilling, Allanah J. Paul, Niklas Virkkala, Tom Hastings, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Tim Boxhammer, Kai G. Schulz, Andrea Ludwig, and Ulf Riebesell
Biogeosciences, 13, 4707–4719, https://doi.org/10.5194/bg-13-4707-2016, https://doi.org/10.5194/bg-13-4707-2016, 2016
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Anthropogenic carbon dioxide (CO2) emissions are reducing the pH in the world's oceans. We determined the plankton community composition and measured primary production, respiration rates and carbon export during an ocean acidification experiment. Our results suggest that increased CO2 reduced respiration and increased net carbon fixation at high CO2. This did not, however, translate into higher carbon export, and consequently did not work as a negative feedback mechanism for decreasing pH.
Allanah J. Paul, Eric P. Achterberg, Lennart T. Bach, Tim Boxhammer, Jan Czerny, Mathias Haunost, Kai-Georg Schulz, Annegret Stuhr, and Ulf Riebesell
Biogeosciences, 13, 3901–3913, https://doi.org/10.5194/bg-13-3901-2016, https://doi.org/10.5194/bg-13-3901-2016, 2016
Anna-Karin Almén, Anu Vehmaa, Andreas Brutemark, Lennart Bach, Silke Lischka, Annegret Stuhr, Sara Furuhagen, Allanah Paul, J. Rafael Bermúdez, Ulf Riebesell, and Jonna Engström-Öst
Biogeosciences, 13, 1037–1048, https://doi.org/10.5194/bg-13-1037-2016, https://doi.org/10.5194/bg-13-1037-2016, 2016
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We studied the effects of ocean acidification (OA) on the aquatic crustacean Eurytemora affinis and measured offspring production in relation to pH, chlorophyll, algae, fatty acids, and oxidative stress. No effects on offspring production or pH effects via food were found. E. affinis seems robust against OA on a physiological level and did probably not face acute pH stress in the treatments, as the species naturally face large pH fluctuations.
A. J. Paul, L. T. Bach, K.-G. Schulz, T. Boxhammer, J. Czerny, E. P. Achterberg, D. Hellemann, Y. Trense, M. Nausch, M. Sswat, and U. Riebesell
Biogeosciences, 12, 6181–6203, https://doi.org/10.5194/bg-12-6181-2015, https://doi.org/10.5194/bg-12-6181-2015, 2015
Ulf Riebesell
Biogeosciences, 22, 2381–2381, https://doi.org/10.5194/bg-22-2381-2025, https://doi.org/10.5194/bg-22-2381-2025, 2025
Librada Ramírez, Leonardo J. Pozzo-Pirotta, Aja Trebec, Víctor Manzanares-Vázquez, José L. Díez, Javier Arístegui, Ulf Riebesell, Stephen D. Archer, and María Segovia
Biogeosciences, 22, 1865–1886, https://doi.org/10.5194/bg-22-1865-2025, https://doi.org/10.5194/bg-22-1865-2025, 2025
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We studied the potential effects of increasing ocean alkalinity on a natural plankton community in subtropical waters of the Atlantic near Gran Canaria, Spain. Alkalinity is the capacity of water to resist acidification, and plankton are usually microscopic plants (phytoplankton) and animals (zooplankton), often less than 2.5 cm in length. This study suggests that increasing ocean alkalinity did not have a significant negative impact on the plankton community studied.
Arthur Vienne, Patrick Frings, Jet Rijnders, Tim Jesper Suhrhoff, Tom Reershemius, Reinaldy P. Poetra, Jens Hartmann, Harun Niron, Miguel Portillo Estrada, Laura Steinwidder, Lucilla Boito, and Sara Vicca
EGUsphere, https://doi.org/10.5194/egusphere-2025-1667, https://doi.org/10.5194/egusphere-2025-1667, 2025
This preprint is open for discussion and under review for SOIL (SOIL).
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Niels Suitner, Jens Hartmann, Selene Varliero, Giulia Faucher, Philipp Suessle, and Charly A. Moras
EGUsphere, https://doi.org/10.5194/egusphere-2025-381, https://doi.org/10.5194/egusphere-2025-381, 2025
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Alkalinity leakage limits the efficiency of ocean alkalinity enhancement. Drivers of this process remain unquantified, restricting accurate assessments. The induced runaway process can be modeled using surface area and aragonite oversaturation as key factors. This study proposes a framework for improving predictability of alkalinity loss due to runaway precipitation, emphasizing the need for field experiments to validate theoretical models concerning dilution and particle sinking processes.
Julieta Schneider, Ulf Riebesell, Charly André Moras, Laura Marín-Samper, Leila Kittu, Joaquín Ortíz-Cortes, and Kai George Schulz
EGUsphere, https://doi.org/10.5194/egusphere-2025-524, https://doi.org/10.5194/egusphere-2025-524, 2025
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Ocean Alkalinity Enhancement (OAE) is an approach to sequester additional atmospheric CO2 in the ocean and may alleviate ocean acidification. A large-scale mesocosm experiment in Norway tested Ca- and Si-based OAE, increasing total alkalinity (TA) by 0–600 µmol kg-1 and measuring CO2 gas exchange. While TA remained stable, we found mineral-type and/or pCO2/pH effects on coccolithophorid calcification, net community production and zooplankton respiration, providing insights for future OAE trials.
Giulia Faucher, Mathias Haunost, Allanah Joy Paul, Anne Ulrike Christiane Tietz, and Ulf Riebesell
Biogeosciences, 22, 405–415, https://doi.org/10.5194/bg-22-405-2025, https://doi.org/10.5194/bg-22-405-2025, 2025
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Ocean alkalinity enhancement (OAE) is being evaluated for its capacity to absorb atmospheric CO2 in the ocean and store it long term to mitigate climate change. As researchers plan for field tests to gain insights into OAE, sharing knowledge on its environmental impact on marine ecosystems is urgent. Our study examined NaOH-induced OAE in Emiliania huxleyi, a key coccolithophore species, and found that the added total alkalinity (ΔTA) should stay below 600 µmol kg⁻¹ to avoid negative impacts.
Philipp Suessle, Jan Taucher, Silvan Urs Goldenberg, Moritz Baumann, Kristian Spilling, Andrea Noche-Ferreira, Mari Vanharanta, and Ulf Riebesell
Biogeosciences, 22, 71–86, https://doi.org/10.5194/bg-22-71-2025, https://doi.org/10.5194/bg-22-71-2025, 2025
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Ocean alkalinity enhancement (OAE) is a negative emission technology which may alter marine communities and the particle export they drive. Here, impacts of carbonate-based OAE on the flux and attenuation of sinking particles in an oligotrophic plankton community are presented. Whilst biological parameters remained unaffected, abiotic carbonate precipitation occurred. Among counteracting OAE’s efficiency, it influenced mineral ballasting and particle sinking velocities, requiring monitoring.
Laura Marín-Samper, Javier Arístegui, Nauzet Hernández-Hernández, and Ulf Riebesell
Biogeosciences, 21, 5707–5724, https://doi.org/10.5194/bg-21-5707-2024, https://doi.org/10.5194/bg-21-5707-2024, 2024
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This study exposed a natural community to two non-CO2-equilibrated ocean alkalinity enhancement (OAE) deployments using different minerals. Adding alkalinity in this manner decreases dissolved CO2, essential for photosynthesis. While photosynthesis was not suppressed, bloom formation was mildly delayed, potentially impacting marine food webs. The study emphasizes the need for further research on OAE without prior equilibration and on its ecological implications.
Niels Suitner, Giulia Faucher, Carl Lim, Julieta Schneider, Charly A. Moras, Ulf Riebesell, and Jens Hartmann
Biogeosciences, 21, 4587–4604, https://doi.org/10.5194/bg-21-4587-2024, https://doi.org/10.5194/bg-21-4587-2024, 2024
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Recent studies described the precipitation of carbonates as a result of alkalinity enhancement in seawater, which could adversely affect the carbon sequestration potential of ocean alkalinity enhancement (OAE) approaches. By conducting experiments in natural seawater, this study observed uniform patterns during the triggered runaway carbonate precipitation, which allow the prediction of safe and efficient local application levels of OAE scenarios.
Silvan Urs Goldenberg, Ulf Riebesell, Daniel Brüggemann, Gregor Börner, Michael Sswat, Arild Folkvord, Maria Couret, Synne Spjelkavik, Nicolás Sánchez, Cornelia Jaspers, and Marta Moyano
Biogeosciences, 21, 4521–4532, https://doi.org/10.5194/bg-21-4521-2024, https://doi.org/10.5194/bg-21-4521-2024, 2024
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Ocean alkalinity enhancement (OAE) is being evaluated as a carbon dioxide removal technology for climate change mitigation. With an experiment on species communities, we show that larval and juvenile fish can be resilient to the resulting perturbation of seawater. Fish may hence recruit successfully and continue to support fisheries' production in regions of OAE. Our findings help to establish an environmentally safe operating space for this ocean-based solution.
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.
Laura Marín-Samper, Javier Arístegui, Nauzet Hernández-Hernández, Joaquín Ortiz, Stephen D. Archer, Andrea Ludwig, and Ulf Riebesell
Biogeosciences, 21, 2859–2876, https://doi.org/10.5194/bg-21-2859-2024, https://doi.org/10.5194/bg-21-2859-2024, 2024
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Our planet is facing a climate crisis. Scientists are working on innovative solutions that will aid in capturing the hard to abate emissions before it is too late. Exciting research reveals that ocean alkalinity enhancement, a key climate change mitigation strategy, does not harm phytoplankton, the cornerstone of marine ecosystems. Through meticulous study, we may have uncovered a positive relationship: up to a specific limit, enhancing ocean alkalinity boosts photosynthesis by certain species.
Aaron Ferderer, Kai G. Schulz, Ulf Riebesell, Kirralee G. Baker, Zanna Chase, and Lennart T. Bach
Biogeosciences, 21, 2777–2794, https://doi.org/10.5194/bg-21-2777-2024, https://doi.org/10.5194/bg-21-2777-2024, 2024
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Ocean alkalinity enhancement (OAE) is a promising method of atmospheric carbon removal; however, its ecological impacts remain largely unknown. We assessed the effects of simulated silicate- and calcium-based mineral OAE on diatom silicification. We found that increased silicate concentrations from silicate-based OAE increased diatom silicification. In contrast, the enhancement of alkalinity had no effect on community silicification and minimal effects on the silicification of different genera.
David González-Santana, María Segovia, Melchor González-Dávila, Librada Ramírez, Aridane G. González, Leonardo J. Pozzo-Pirotta, Veronica Arnone, Victor Vázquez, Ulf Riebesell, and J. Magdalena Santana-Casiano
Biogeosciences, 21, 2705–2715, https://doi.org/10.5194/bg-21-2705-2024, https://doi.org/10.5194/bg-21-2705-2024, 2024
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In a recent experiment off the coast of Gran Canaria (Spain), scientists explored a method called ocean alkalinization enhancement (OAE), where carbonate minerals were added to seawater. This process changed the levels of certain ions in the water, affecting its pH and buffering capacity. The researchers were particularly interested in how this could impact the levels of essential trace metals in the water.
Annika Nolte, Ezra Haaf, Benedikt Heudorfer, Steffen Bender, and Jens Hartmann
Hydrol. Earth Syst. Sci., 28, 1215–1249, https://doi.org/10.5194/hess-28-1215-2024, https://doi.org/10.5194/hess-28-1215-2024, 2024
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This study examines about 8000 groundwater level (GWL) time series from five continents to explore similarities in groundwater systems at different scales. Statistical metrics and machine learning techniques are applied to identify common GWL dynamics patterns and analyze their controlling factors. The study also highlights the potential and limitations of this data-driven approach to improve our understanding of groundwater recharge and discharge processes.
Xiaoke Xin, Giulia Faucher, and Ulf Riebesell
Biogeosciences, 21, 761–772, https://doi.org/10.5194/bg-21-761-2024, https://doi.org/10.5194/bg-21-761-2024, 2024
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Ocean alkalinity enhancement (OAE) is a promising approach to remove CO2 by accelerating natural rock weathering. However, some of the alkaline substances contain trace metals which could be toxic to marine life. By exposing three representative phytoplankton species to Ni released from alkaline materials, we observed varying responses of phytoplankton to nickel concentrations, suggesting caution should be taken and toxic thresholds should be avoided in OAE with Ni-rich materials.
Ulf Riebesell, Daniela Basso, Sonja Geilert, Andrew W. Dale, and Matthias Kreuzburg
State Planet, 2-oae2023, 6, https://doi.org/10.5194/sp-2-oae2023-6-2023, https://doi.org/10.5194/sp-2-oae2023-6-2023, 2023
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Mesocosm experiments represent a highly valuable tool in determining the safe operating space of ocean alkalinity enhancement (OAE) applications. By combining realism and biological complexity with controllability and replication, they provide an ideal OAE test bed and a critical stepping stone towards field applications. Mesocosm approaches can also be helpful in testing the efficacy, efficiency and permanence of OAE applications.
Nele Lehmann, Hugues Lantuit, Michael Ernst Böttcher, Jens Hartmann, Antje Eulenburg, and Helmuth Thomas
Biogeosciences, 20, 3459–3479, https://doi.org/10.5194/bg-20-3459-2023, https://doi.org/10.5194/bg-20-3459-2023, 2023
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Riverine alkalinity in the silicate-dominated headwater catchment at subarctic Iskorasfjellet, northern Norway, was almost entirely derived from weathering of minor carbonate occurrences in the riparian zone. The uphill catchment appeared limited by insufficient contact time of weathering agents and weatherable material. Further, alkalinity increased with decreasing permafrost extent. Thus, with climate change, alkalinity generation is expected to increase in this permafrost-degrading landscape.
Mingyang Tian, Jens Hartmann, Gibran Romero-Mujalli, Thorben Amann, Lishan Ran, and Ji-Hyung Park
Biogeosciences Discuss., https://doi.org/10.5194/bg-2023-131, https://doi.org/10.5194/bg-2023-131, 2023
Manuscript not accepted for further review
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Effective water quality management in the Elbe River from 1984 to 2018 significantly reduced CO2 emissions, particularly after Germany's reunification. Key factors in the reduction include organic carbon removal and nutrient management, with nitrogen control being more critical than phosphorus for the restoration of ecosystem capacity. Unpredictable influxes of organic carbon and the relocation of emissions from wastewater treatment can cause uncertainties for CO2 removals.
Moritz Baumann, Allanah Joy Paul, Jan Taucher, Lennart Thomas Bach, Silvan Goldenberg, Paul Stange, Fabrizio Minutolo, and Ulf Riebesell
Biogeosciences, 20, 2595–2612, https://doi.org/10.5194/bg-20-2595-2023, https://doi.org/10.5194/bg-20-2595-2023, 2023
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The sinking velocity of marine particles affects how much atmospheric CO2 is stored inside our oceans. We measured particle sinking velocities in the Peruvian upwelling system and assessed their physical and biochemical drivers. We found that sinking velocity was mainly influenced by particle size and porosity, while ballasting minerals played only a minor role. Our findings help us to better understand the particle sinking dynamics in this highly productive marine system.
Matteo Willeit, Tatiana Ilyina, Bo Liu, Christoph Heinze, Mahé Perrette, Malte Heinemann, Daniela Dalmonech, Victor Brovkin, Guy Munhoven, Janine Börker, Jens Hartmann, Gibran Romero-Mujalli, and Andrey Ganopolski
Geosci. Model Dev., 16, 3501–3534, https://doi.org/10.5194/gmd-16-3501-2023, https://doi.org/10.5194/gmd-16-3501-2023, 2023
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In this paper we present the carbon cycle component of the newly developed fast Earth system model CLIMBER-X. The model can be run with interactive atmospheric CO2 to investigate the feedbacks between climate and the carbon cycle on temporal scales ranging from decades to > 100 000 years. CLIMBER-X is expected to be a useful tool for studying past climate–carbon cycle changes and for the investigation of the long-term future evolution of the Earth system.
Kristian Spilling, Jonna Piiparinen, Eric P. Achterberg, Javier Arístegui, Lennart T. Bach, Maria T. Camarena-Gómez, Elisabeth von der Esch, Martin A. Fischer, Markel Gómez-Letona, Nauzet Hernández-Hernández, Judith Meyer, Ruth A. Schmitz, and Ulf Riebesell
Biogeosciences, 20, 1605–1619, https://doi.org/10.5194/bg-20-1605-2023, https://doi.org/10.5194/bg-20-1605-2023, 2023
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We carried out an enclosure experiment using surface water off Peru with different additions of oxygen minimum zone water. In this paper, we report on enzyme activity and provide data on the decomposition of organic matter. We found very high activity with respect to an enzyme breaking down protein, suggesting that this is important for nutrient recycling both at present and in the future ocean.
Markus A. Min, David M. Needham, Sebastian Sudek, Nathan Kobun Truelove, Kathleen J. Pitz, Gabriela M. Chavez, Camille Poirier, Bente Gardeler, Elisabeth von der Esch, Andrea Ludwig, Ulf Riebesell, Alexandra Z. Worden, and Francisco P. Chavez
Biogeosciences, 20, 1277–1298, https://doi.org/10.5194/bg-20-1277-2023, https://doi.org/10.5194/bg-20-1277-2023, 2023
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Emerging molecular methods provide new ways of understanding how marine communities respond to changes in ocean conditions. Here, environmental DNA was used to track the temporal evolution of biological communities in the Peruvian coastal upwelling system and in an adjacent enclosure where upwelling was simulated. We found that the two communities quickly diverged, with the open ocean being one found during upwelling and the enclosure evolving to one found under stratified conditions.
Jens Hartmann, Niels Suitner, Carl Lim, Julieta Schneider, Laura Marín-Samper, Javier Arístegui, Phil Renforth, Jan Taucher, and Ulf Riebesell
Biogeosciences, 20, 781–802, https://doi.org/10.5194/bg-20-781-2023, https://doi.org/10.5194/bg-20-781-2023, 2023
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CO2 can be stored in the ocean via increasing alkalinity of ocean water. Alkalinity can be created via dissolution of alkaline materials, like limestone or soda. Presented research studies boundaries for increasing alkalinity in seawater. The best way to increase alkalinity was found using an equilibrated solution, for example as produced from reactors. Adding particles for dissolution into seawater on the other hand produces the risk of losing alkalinity and degassing of CO2 to the atmosphere.
Shuang Gao, Jörg Schwinger, Jerry Tjiputra, Ingo Bethke, Jens Hartmann, Emilio Mayorga, and Christoph Heinze
Biogeosciences, 20, 93–119, https://doi.org/10.5194/bg-20-93-2023, https://doi.org/10.5194/bg-20-93-2023, 2023
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We assess the impact of riverine nutrients and carbon (C) on projected marine primary production (PP) and C uptake using a fully coupled Earth system model. Riverine inputs alleviate nutrient limitation and thus lessen the projected PP decline by up to 0.7 Pg C yr−1 globally. The effect of increased riverine C may be larger than the effect of nutrient inputs in the future on the projected ocean C uptake, while in the historical period increased nutrient inputs are considered the largest driver.
Allanah Joy Paul, Lennart Thomas Bach, Javier Arístegui, Elisabeth von der Esch, Nauzet Hernández-Hernández, Jonna Piiparinen, Laura Ramajo, Kristian Spilling, and Ulf Riebesell
Biogeosciences, 19, 5911–5926, https://doi.org/10.5194/bg-19-5911-2022, https://doi.org/10.5194/bg-19-5911-2022, 2022
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We investigated how different deep water chemistry and biology modulate the response of surface phytoplankton communities to upwelling in the Peruvian coastal zone. Our results show that the most influential drivers were the ratio of inorganic nutrients (N : P) and the microbial community present in upwelling source water. These led to unexpected and variable development in the phytoplankton assemblage that could not be predicted by the amount of inorganic nutrients alone.
Shao-Min Chen, Ulf Riebesell, Kai G. Schulz, Elisabeth von der Esch, Eric P. Achterberg, and Lennart T. Bach
Biogeosciences, 19, 295–312, https://doi.org/10.5194/bg-19-295-2022, https://doi.org/10.5194/bg-19-295-2022, 2022
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Oxygen minimum zones in the ocean are characterized by enhanced carbon dioxide (CO2) levels and are being further acidified by increasing anthropogenic atmospheric CO2. Here we report CO2 system measurements in a mesocosm study offshore Peru during a rare coastal El Niño event to investigate how CO2 dynamics may respond to ongoing ocean deoxygenation. Our observations show that nitrogen limitation, productivity, and plankton community shift play an important role in driving the CO2 dynamics.
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.
Lennart Thomas Bach, Allanah Joy Paul, Tim Boxhammer, Elisabeth von der Esch, Michelle Graco, Kai Georg Schulz, Eric Achterberg, Paulina Aguayo, Javier Arístegui, Patrizia Ayón, Isabel Baños, Avy Bernales, Anne Sophie Boegeholz, Francisco Chavez, Gabriela Chavez, Shao-Min Chen, Kristin Doering, Alba Filella, Martin Fischer, Patricia Grasse, Mathias Haunost, Jan Hennke, Nauzet Hernández-Hernández, Mark Hopwood, Maricarmen Igarza, Verena Kalter, Leila Kittu, Peter Kohnert, Jesus Ledesma, Christian Lieberum, Silke Lischka, Carolin Löscher, Andrea Ludwig, Ursula Mendoza, Jana Meyer, Judith Meyer, Fabrizio Minutolo, Joaquin Ortiz Cortes, Jonna Piiparinen, Claudia Sforna, Kristian Spilling, Sonia Sanchez, Carsten Spisla, Michael Sswat, Mabel Zavala Moreira, and Ulf Riebesell
Biogeosciences, 17, 4831–4852, https://doi.org/10.5194/bg-17-4831-2020, https://doi.org/10.5194/bg-17-4831-2020, 2020
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The eastern boundary upwelling system off Peru is among Earth's most productive ocean ecosystems, but the factors that control its functioning are poorly constrained. Here we used mesocosms, moored ~ 6 km offshore Peru, to investigate how processes in plankton communities drive key biogeochemical processes. We show that nutrient and light co-limitation keep productivity and export at a remarkably constant level while stoichiometry changes strongly with shifts in plankton community structure.
Giulia Faucher, Ulf Riebesell, and Lennart Thomas Bach
Clim. Past, 16, 1007–1025, https://doi.org/10.5194/cp-16-1007-2020, https://doi.org/10.5194/cp-16-1007-2020, 2020
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We designed five experiments choosing different coccolithophore species that have been evolutionarily distinct for millions of years. If all species showed the same morphological response to an environmental driver, this could be indicative of a response pattern that is conserved over geological timescales. We found an increase in the percentage of malformed coccoliths under altered CO2, providing evidence that this response could be used as paleo-proxy for episodes of acute CO2 perturbations.
Wagner de Oliveira Garcia, Thorben Amann, Jens Hartmann, Kristine Karstens, Alexander Popp, Lena R. Boysen, Pete Smith, and Daniel Goll
Biogeosciences, 17, 2107–2133, https://doi.org/10.5194/bg-17-2107-2020, https://doi.org/10.5194/bg-17-2107-2020, 2020
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Biomass-based terrestrial negative emission technologies (tNETS) have high potential to sequester CO2. Many CO2 uptake estimates do not include the effect of nutrient deficiencies in soils on biomass production. We show that nutrients can be partly resupplied by enhanced weathering (EW) rock powder application, increasing the effectiveness of tNETs. Depending on the deployed amounts of rock powder, EW could also improve soil hydrology, adding a new dimension to the coupling of tNETs with EW.
Thorben Amann, Jens Hartmann, Eric Struyf, Wagner de Oliveira Garcia, Elke K. Fischer, Ivan Janssens, Patrick Meire, and Jonas Schoelynck
Biogeosciences, 17, 103–119, https://doi.org/10.5194/bg-17-103-2020, https://doi.org/10.5194/bg-17-103-2020, 2020
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Weathering is a major control on atmospheric CO2 at geologic timescales. Enhancement of this process can be used to actively remove CO2 from the atmosphere. Field results are still scarce and with this experiment we try to add some near-natural insights into dissolution processes. Results show CO2 sequestration potentials but also highlight the strong variability of outcomes that can be expected in natural environments. Such experiments are of the utmost importance to identify key processes.
Fabrice Lacroix, Tatiana Ilyina, and Jens Hartmann
Biogeosciences, 17, 55–88, https://doi.org/10.5194/bg-17-55-2020, https://doi.org/10.5194/bg-17-55-2020, 2020
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Contributions of rivers to the oceanic cycling of carbon have been poorly represented in global models until now. Here, we assess the long–term implications of preindustrial riverine loads in the ocean in a novel framework which estimates the loads through a hierarchy of weathering and land–ocean export models. We investigate their impacts for the oceanic biological production and air–sea carbon flux. Finally, we assess the potential incorporation of the framework in an Earth system model.
Thorben Amann and Jens Hartmann
Biogeosciences, 16, 2949–2960, https://doi.org/10.5194/bg-16-2949-2019, https://doi.org/10.5194/bg-16-2949-2019, 2019
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With the recent publication of the IPCC special report on the 1.5 °C target and increased attention on carbon dioxide removal (CDR) technologies, we think it is time to advance from the current way of looking at specific strategies to a more holistic CDR perspective, since multiple "side effects" may lead to additional CO2 uptake into different carbon pools. This paper explores potential co-benefits between terrestrial CDR strategies to facilitate a maximum CO2 sequestration effect.
Janine Börker, Jens Hartmann, Gibran Romero-Mujalli, and Gaojun Li
Earth Surf. Dynam., 7, 191–197, https://doi.org/10.5194/esurf-7-191-2019, https://doi.org/10.5194/esurf-7-191-2019, 2019
Yilong Wang, Philippe Ciais, Daniel Goll, Yuanyuan Huang, Yiqi Luo, Ying-Ping Wang, A. Anthony Bloom, Grégoire Broquet, Jens Hartmann, Shushi Peng, Josep Penuelas, Shilong Piao, Jordi Sardans, Benjamin D. Stocker, Rong Wang, Sönke Zaehle, and Sophie Zechmeister-Boltenstern
Geosci. Model Dev., 11, 3903–3928, https://doi.org/10.5194/gmd-11-3903-2018, https://doi.org/10.5194/gmd-11-3903-2018, 2018
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We present a new modeling framework called Global Observation-based Land-ecosystems Utilization Model of Carbon, Nitrogen and Phosphorus (GOLUM-CNP) that combines a data-constrained C-cycle analysis with data-driven estimates of N and P inputs and losses and with observed stoichiometric ratios. GOLUM-CNP provides a traceable tool, where a consistency between different datasets of global C, N, and P cycles has been achieved.
Yong Zhang, Lennart T. Bach, Kai T. Lohbeck, Kai G. Schulz, Luisa Listmann, Regina Klapper, and Ulf Riebesell
Biogeosciences, 15, 3691–3701, https://doi.org/10.5194/bg-15-3691-2018, https://doi.org/10.5194/bg-15-3691-2018, 2018
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To compare variations in physiological responses to pCO2 between populations, we measured growth, POC and PIC production rates at a pCO2 range from 120 to 2630 µatm for 17 strains of the coccolithophore Emiliania huxleyi from the Azores, Canary Islands, and Norwegian coast near Bergen. Optimal pCO2 for growth and POC production rates and tolerance to low pH was significantly higher for the Bergen population than the Azores and Canary Islands populations.
Ji-Hyung Park, Omme K. Nayna, Most S. Begum, Eliyan Chea, Jens Hartmann, Richard G. Keil, Sanjeev Kumar, Xixi Lu, Lishan Ran, Jeffrey E. Richey, Vedula V. S. S. Sarma, Shafi M. Tareq, Do Thi Xuan, and Ruihong Yu
Biogeosciences, 15, 3049–3069, https://doi.org/10.5194/bg-15-3049-2018, https://doi.org/10.5194/bg-15-3049-2018, 2018
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Human activities are drastically altering water and material flows in river systems across Asia. This review provides a conceptual framework for assessing the human impacts on Asian river C fluxes and an update on anthropogenic alterations of riverine C fluxes, focusing on the impacts of water pollution and river impoundments on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia.
Katharine J. Crawfurd, Santiago Alvarez-Fernandez, Kristina D. A. Mojica, Ulf Riebesell, and Corina P. D. Brussaard
Biogeosciences, 14, 3831–3849, https://doi.org/10.5194/bg-14-3831-2017, https://doi.org/10.5194/bg-14-3831-2017, 2017
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Carbon dioxide (CO2) is increasing in the atmosphere and oceans. To simulate future conditions we manipulated CO2 concentrations of natural Baltic seawater in 55 m3 bags in situ. We saw increased growth rates and abundances of the smallest-sized eukaryotic phytoplankton and reduced abundances of other phytoplankton with increased CO2. Viral and bacterial abundances were also affected. This would lead to more carbon recycling in the surface water and affect marine food webs and the carbon cycle.
Jakob Zscheischler, Miguel D. Mahecha, Valerio Avitabile, Leonardo Calle, Nuno Carvalhais, Philippe Ciais, Fabian Gans, Nicolas Gruber, Jens Hartmann, Martin Herold, Kazuhito Ichii, Martin Jung, Peter Landschützer, Goulven G. Laruelle, Ronny Lauerwald, Dario Papale, Philippe Peylin, Benjamin Poulter, Deepak Ray, Pierre Regnier, Christian Rödenbeck, Rosa M. Roman-Cuesta, Christopher Schwalm, Gianluca Tramontana, Alexandra Tyukavina, Riccardo Valentini, Guido van der Werf, Tristram O. West, Julie E. Wolf, and Markus Reichstein
Biogeosciences, 14, 3685–3703, https://doi.org/10.5194/bg-14-3685-2017, https://doi.org/10.5194/bg-14-3685-2017, 2017
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Here we synthesize a wide range of global spatiotemporal observational data on carbon exchanges between the Earth surface and the atmosphere. A key challenge was to consistently combining observational products of terrestrial and aquatic surfaces. Our primary goal is to identify today’s key uncertainties and observational shortcomings that would need to be addressed in future measurement campaigns or expansions of in situ observatories.
Giulia Faucher, Linn Hoffmann, Lennart T. Bach, Cinzia Bottini, Elisabetta Erba, and Ulf Riebesell
Biogeosciences, 14, 3603–3613, https://doi.org/10.5194/bg-14-3603-2017, https://doi.org/10.5194/bg-14-3603-2017, 2017
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The main goal of this study was to understand if, similarly to the fossil record, high quantities of toxic metals induce coccolith dwarfism in coccolithophore species. We investigated, for the first time, the effects of trace metals on coccolithophore species other than E. huxleyi and on coccolith morphology and size. Our data show a species-specific sensitivity to trace metal concentration, allowing the recognition of the most-, intermediate- and least-tolerant taxa to trace metal enrichments.
Silke Lischka, Lennart T. Bach, Kai-Georg Schulz, and Ulf Riebesell
Biogeosciences, 14, 447–466, https://doi.org/10.5194/bg-14-447-2017, https://doi.org/10.5194/bg-14-447-2017, 2017
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We conducted a large-scale field experiment using 55 m3 floating containers (mesocosms) to investigate consequences of near-future projected CO2 elevations (ocean acidification) on a Baltic Sea plankton community in Storfjärden (Finland). The focus of our study was on single- and multicelled small-sized organisms dwelling in the water column. Our results suggest that increasing CO2 concentrations may change the species composition and promote specific food web interactions.
Enis Hrustić, Risto Lignell, Ulf Riebesell, and Tron Frede Thingstad
Biogeosciences, 14, 379–387, https://doi.org/10.5194/bg-14-379-2017, https://doi.org/10.5194/bg-14-379-2017, 2017
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Phytoplankton in the ocean's stratified layer are limited by mineral nutrients, normally nitrogen, phosphorus, or iron. It is important to know not only which element is limiting, but also the surplus of the secondary limiting element. We explore here, in temperate mesotrophic waters, a bioassay based on alkaline phosphatase that provides information on both of these.
Thomas Hornick, Lennart T. Bach, Katharine J. Crawfurd, Kristian Spilling, Eric P. Achterberg, Jason N. Woodhouse, Kai G. Schulz, Corina P. D. Brussaard, Ulf Riebesell, and Hans-Peter Grossart
Biogeosciences, 14, 1–15, https://doi.org/10.5194/bg-14-1-2017, https://doi.org/10.5194/bg-14-1-2017, 2017
Rafael Bermúdez, Monika Winder, Annegret Stuhr, Anna-Karin Almén, Jonna Engström-Öst, and Ulf Riebesell
Biogeosciences, 13, 6625–6635, https://doi.org/10.5194/bg-13-6625-2016, https://doi.org/10.5194/bg-13-6625-2016, 2016
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Increasing CO2 is changing seawater chemistry towards a lower pH, which affects marine organisms. We investigate the response of a brackish plankton community to a CO2 gradient in terms of structure and fatty acid composition. The structure was resilient to CO2 and did not diverge between treatments. FA was influenced by community structure, which was driven by silicate and phosphate. This suggests that CO2 effects are dampened in communities already experiencing high natural pCO2 fluctuation.
Anu Vehmaa, Anna-Karin Almén, Andreas Brutemark, Allanah Paul, Ulf Riebesell, Sara Furuhagen, and Jonna Engström-Öst
Biogeosciences, 13, 6171–6182, https://doi.org/10.5194/bg-13-6171-2016, https://doi.org/10.5194/bg-13-6171-2016, 2016
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Ocean acidification is challenging phenotypic plasticity of individuals and populations. We studied phenotypic plasticity of the calanoid copepod Acartia bifilosa in the course of a pelagic, large-volume mesocosm study in the Baltic Sea. We found significant negative effects of ocean acidification on adult female copepod size and egg hatching success. Overall, these results indicate that A. bifilosa could be affected by projected near-future CO2 levels.
Kristian Spilling, Kai G. Schulz, Allanah J. Paul, Tim Boxhammer, Eric P. Achterberg, Thomas Hornick, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Kate Crawfurd, Corina P. D. Brussaard, Hans-Peter Grossart, and Ulf Riebesell
Biogeosciences, 13, 6081–6093, https://doi.org/10.5194/bg-13-6081-2016, https://doi.org/10.5194/bg-13-6081-2016, 2016
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We performed an experiment in the Baltic Sea in order to investigate the consequences of the increasing CO2 levels on biological processes in the free water mass. There was more accumulation of organic carbon at high CO2 levels. Surprisingly, this was caused by reduced loss processes (respiration and bacterial production) in a high-CO2 environment, and not by increased photosynthetic fixation of CO2. Our carbon budget can be used to better disentangle the effects of ocean acidification.
Kristian Spilling, Allanah J. Paul, Niklas Virkkala, Tom Hastings, Silke Lischka, Annegret Stuhr, Rafael Bermúdez, Jan Czerny, Tim Boxhammer, Kai G. Schulz, Andrea Ludwig, and Ulf Riebesell
Biogeosciences, 13, 4707–4719, https://doi.org/10.5194/bg-13-4707-2016, https://doi.org/10.5194/bg-13-4707-2016, 2016
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Anthropogenic carbon dioxide (CO2) emissions are reducing the pH in the world's oceans. We determined the plankton community composition and measured primary production, respiration rates and carbon export during an ocean acidification experiment. Our results suggest that increased CO2 reduced respiration and increased net carbon fixation at high CO2. This did not, however, translate into higher carbon export, and consequently did not work as a negative feedback mechanism for decreasing pH.
Juntian Xu, Lennart T. Bach, Kai G. Schulz, Wenyan Zhao, Kunshan Gao, and Ulf Riebesell
Biogeosciences, 13, 4637–4643, https://doi.org/10.5194/bg-13-4637-2016, https://doi.org/10.5194/bg-13-4637-2016, 2016
Alison L. Webb, Emma Leedham-Elvidge, Claire Hughes, Frances E. Hopkins, Gill Malin, Lennart T. Bach, Kai Schulz, Kate Crawfurd, Corina P. D. Brussaard, Annegret Stuhr, Ulf Riebesell, and Peter S. Liss
Biogeosciences, 13, 4595–4613, https://doi.org/10.5194/bg-13-4595-2016, https://doi.org/10.5194/bg-13-4595-2016, 2016
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This paper presents concentrations of several trace gases produced by the Baltic Sea phytoplankton community during a mesocosm experiment with five different CO2 levels. Average concentrations of dimethylsulphide were lower in the highest CO2 mesocosms over a 6-week period, corresponding to previous mesocosm experiment results. No dimethylsulfoniopropionate was detected due to a methodological issue. Concentrations of iodine- and bromine-containing halocarbons were unaffected by increasing CO2.
Allanah J. Paul, Eric P. Achterberg, Lennart T. Bach, Tim Boxhammer, Jan Czerny, Mathias Haunost, Kai-Georg Schulz, Annegret Stuhr, and Ulf Riebesell
Biogeosciences, 13, 3901–3913, https://doi.org/10.5194/bg-13-3901-2016, https://doi.org/10.5194/bg-13-3901-2016, 2016
Carolin R. Löscher, Hermann W. Bange, Ruth A. Schmitz, Cameron M. Callbeck, Anja Engel, Helena Hauss, Torsten Kanzow, Rainer Kiko, Gaute Lavik, Alexandra Loginova, Frank Melzner, Judith Meyer, Sven C. Neulinger, Markus Pahlow, Ulf Riebesell, Harald Schunck, Sören Thomsen, and Hannes Wagner
Biogeosciences, 13, 3585–3606, https://doi.org/10.5194/bg-13-3585-2016, https://doi.org/10.5194/bg-13-3585-2016, 2016
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The ocean loses oxygen due to climate change. Addressing this issue in tropical ocean regions (off Peru and Mauritania), we aimed to understand the effects of oxygen depletion on various aspects of marine biogeochemistry, including primary production and export production, the nitrogen cycle, greenhouse gas production, organic matter fluxes and remineralization, and the role of zooplankton and viruses.
Monika Nausch, Lennart Thomas Bach, Jan Czerny, Josephine Goldstein, Hans-Peter Grossart, Dana Hellemann, Thomas Hornick, Eric Pieter Achterberg, Kai-Georg Schulz, and Ulf Riebesell
Biogeosciences, 13, 3035–3050, https://doi.org/10.5194/bg-13-3035-2016, https://doi.org/10.5194/bg-13-3035-2016, 2016
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Studies investigating the effect of increasing CO2 levels on the phosphorus cycle in natural waters are lacking although phosphorus often controls phytoplankton development in aquatic systems. The aim of our study was to analyse effects of elevated CO2 levels on phosphorus pool sizes and uptake. Therefore, we conducted a CO2-manipulation mesocosm experiment in the Storfjärden (western Gulf of Finland, Baltic Sea) in summer 2012. We compared the phosphorus dynamics in different mesocosm treatment
Tim Boxhammer, Lennart T. Bach, Jan Czerny, and Ulf Riebesell
Biogeosciences, 13, 2849–2858, https://doi.org/10.5194/bg-13-2849-2016, https://doi.org/10.5194/bg-13-2849-2016, 2016
Anna-Karin Almén, Anu Vehmaa, Andreas Brutemark, Lennart Bach, Silke Lischka, Annegret Stuhr, Sara Furuhagen, Allanah Paul, J. Rafael Bermúdez, Ulf Riebesell, and Jonna Engström-Öst
Biogeosciences, 13, 1037–1048, https://doi.org/10.5194/bg-13-1037-2016, https://doi.org/10.5194/bg-13-1037-2016, 2016
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We studied the effects of ocean acidification (OA) on the aquatic crustacean Eurytemora affinis and measured offspring production in relation to pH, chlorophyll, algae, fatty acids, and oxidative stress. No effects on offspring production or pH effects via food were found. E. affinis seems robust against OA on a physiological level and did probably not face acute pH stress in the treatments, as the species naturally face large pH fluctuations.
J. Meyer, C. R. Löscher, S. C. Neulinger, A. F. Reichel, A. Loginova, C. Borchard, R. A. Schmitz, H. Hauss, R. Kiko, and U. Riebesell
Biogeosciences, 13, 781–794, https://doi.org/10.5194/bg-13-781-2016, https://doi.org/10.5194/bg-13-781-2016, 2016
M. N. Müller, J. Barcelos e Ramos, K. G. Schulz, U. Riebesell, J. Kaźmierczak, F. Gallo, L. Mackinder, Y. Li, P. N. Nesterenko, T. W. Trull, and G. M. Hallegraeff
Biogeosciences, 12, 6493–6501, https://doi.org/10.5194/bg-12-6493-2015, https://doi.org/10.5194/bg-12-6493-2015, 2015
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The White Cliffs of Dover date back to the Cretaceous and are made up of microscopic chalky shells which were produced mainly by marine phytoplankton (coccolithophores). This is iconic proof for their success at times of relatively high seawater calcium concentrations and, as shown here, to be linked to their ability to precipitate calcium as chalk. The invention of calcification can thus be considered an evolutionary milestone allowing coccolithophores to thrive at times when others struggled.
A. Singh, S. E. Baer, U. Riebesell, A. C. Martiny, and M. W. Lomas
Biogeosciences, 12, 6389–6403, https://doi.org/10.5194/bg-12-6389-2015, https://doi.org/10.5194/bg-12-6389-2015, 2015
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Stoichiometry of macronutrients in the subtropical ocean is important to understand how biogeochemical cycles are coupled. We observed that elemental stoichiometry was much higher in the dissolved organic-matter pools than in the particulate organic matter pools. In addition ratios vary with depth due to changes in growth rates of specific phytoplankton groups, namely cyanobacteria. These data will improve biogeochemical models by placing observational constraints on these ratios.
A. J. Paul, L. T. Bach, K.-G. Schulz, T. Boxhammer, J. Czerny, E. P. Achterberg, D. Hellemann, Y. Trense, M. Nausch, M. Sswat, and U. Riebesell
Biogeosciences, 12, 6181–6203, https://doi.org/10.5194/bg-12-6181-2015, https://doi.org/10.5194/bg-12-6181-2015, 2015
J. Meyer and U. Riebesell
Biogeosciences, 12, 1671–1682, https://doi.org/10.5194/bg-12-1671-2015, https://doi.org/10.5194/bg-12-1671-2015, 2015
G. G. Laruelle, R. Lauerwald, J. Rotschi, P. A. Raymond, J. Hartmann, and P. Regnier
Biogeosciences, 12, 1447–1458, https://doi.org/10.5194/bg-12-1447-2015, https://doi.org/10.5194/bg-12-1447-2015, 2015
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This study quantifies the exchange of carbon dioxide (CO2) between the atmosphere and the land-ocean aquatic continuum (LOAC) of the northeast North American coast, which consists of rivers, estuaries, and the coastal ocean. Our analysis reveals significant variations of the flux intensity both in time and space across the study area. Ice cover, snowmelt, and the intensity of the estuarine filter are identified as important control factors of the CO2 exchange along the LOAC.
S. A. Krueger-Hadfield, C. Balestreri, J. Schroeder, A. Highfield, P. Helaouët, J. Allum, R. Moate, K. T. Lohbeck, P. I. Miller, U. Riebesell, T. B. H. Reusch, R. E. M. Rickaby, J. Young, G. Hallegraeff, C. Brownlee, and D. C. Schroeder
Biogeosciences, 11, 5215–5234, https://doi.org/10.5194/bg-11-5215-2014, https://doi.org/10.5194/bg-11-5215-2014, 2014
M. N. Müller, M. Lebrato, U. Riebesell, J. Barcelos e Ramos, K. G. Schulz, S. Blanco-Ameijeiras, S. Sett, A. Eisenhauer, and H. M. Stoll
Biogeosciences, 11, 1065–1075, https://doi.org/10.5194/bg-11-1065-2014, https://doi.org/10.5194/bg-11-1065-2014, 2014
R. Valentini, A. Arneth, A. Bombelli, S. Castaldi, R. Cazzolla Gatti, F. Chevallier, P. Ciais, E. Grieco, J. Hartmann, M. Henry, R. A. Houghton, M. Jung, W. L. Kutsch, Y. Malhi, E. Mayorga, L. Merbold, G. Murray-Tortarolo, D. Papale, P. Peylin, B. Poulter, P. A. Raymond, M. Santini, S. Sitch, G. Vaglio Laurin, G. R. van der Werf, C. A. Williams, and R. J. Scholes
Biogeosciences, 11, 381–407, https://doi.org/10.5194/bg-11-381-2014, https://doi.org/10.5194/bg-11-381-2014, 2014
A. Silyakova, R. G. J. Bellerby, K. G. Schulz, J. Czerny, T. Tanaka, G. Nondal, U. Riebesell, A. Engel, T. De Lange, and A. Ludvig
Biogeosciences, 10, 4847–4859, https://doi.org/10.5194/bg-10-4847-2013, https://doi.org/10.5194/bg-10-4847-2013, 2013
G. G. Laruelle, H. H. Dürr, R. Lauerwald, J. Hartmann, C. P. Slomp, N. Goossens, and P. A. G. Regnier
Hydrol. Earth Syst. Sci., 17, 2029–2051, https://doi.org/10.5194/hess-17-2029-2013, https://doi.org/10.5194/hess-17-2029-2013, 2013
J. A. Collins, A. Govin, S. Mulitza, D. Heslop, M. Zabel, J. Hartmann, U. Röhl, and G. Wefer
Clim. Past, 9, 1181–1191, https://doi.org/10.5194/cp-9-1181-2013, https://doi.org/10.5194/cp-9-1181-2013, 2013
J. Czerny, K. G. Schulz, T. Boxhammer, R. G. J. Bellerby, J. Büdenbender, A. Engel, S. A. Krug, A. Ludwig, K. Nachtigall, G. Nondal, B. Niehoff, A. Silyakova, and U. Riebesell
Biogeosciences, 10, 3109–3125, https://doi.org/10.5194/bg-10-3109-2013, https://doi.org/10.5194/bg-10-3109-2013, 2013
J. Czerny, K. G. Schulz, S. A. Krug, A. Ludwig, and U. Riebesell
Biogeosciences, 10, 1937–1941, https://doi.org/10.5194/bg-10-1937-2013, https://doi.org/10.5194/bg-10-1937-2013, 2013
U. Riebesell, J. Czerny, K. von Bröckel, T. Boxhammer, J. Büdenbender, M. Deckelnick, M. Fischer, D. Hoffmann, S. A. Krug, U. Lentz, A. Ludwig, R. Muche, and K. G. Schulz
Biogeosciences, 10, 1835–1847, https://doi.org/10.5194/bg-10-1835-2013, https://doi.org/10.5194/bg-10-1835-2013, 2013
N. Aberle, K. G. Schulz, A. Stuhr, A. M. Malzahn, A. Ludwig, and U. Riebesell
Biogeosciences, 10, 1471–1481, https://doi.org/10.5194/bg-10-1471-2013, https://doi.org/10.5194/bg-10-1471-2013, 2013
A. de Kluijver, K. Soetaert, J. Czerny, K. G. Schulz, T. Boxhammer, U. Riebesell, and J. J. Middelburg
Biogeosciences, 10, 1425–1440, https://doi.org/10.5194/bg-10-1425-2013, https://doi.org/10.5194/bg-10-1425-2013, 2013
A. Engel, C. Borchard, J. Piontek, K. G. Schulz, U. Riebesell, and R. Bellerby
Biogeosciences, 10, 1291–1308, https://doi.org/10.5194/bg-10-1291-2013, https://doi.org/10.5194/bg-10-1291-2013, 2013
C. P. D. Brussaard, A. A. M. Noordeloos, H. Witte, M. C. J. Collenteur, K. Schulz, A. Ludwig, and U. Riebesell
Biogeosciences, 10, 719–731, https://doi.org/10.5194/bg-10-719-2013, https://doi.org/10.5194/bg-10-719-2013, 2013
A.-S. Roy, S. M. Gibbons, H. Schunck, S. Owens, J. G. Caporaso, M. Sperling, J. I. Nissimov, S. Romac, L. Bittner, M. Mühling, U. Riebesell, J. LaRoche, and J. A. Gilbert
Biogeosciences, 10, 555–566, https://doi.org/10.5194/bg-10-555-2013, https://doi.org/10.5194/bg-10-555-2013, 2013
P. K. Patra, J. G. Canadell, R. A. Houghton, S. L. Piao, N.-H. Oh, P. Ciais, K. R. Manjunath, A. Chhabra, T. Wang, T. Bhattacharya, P. Bousquet, J. Hartman, A. Ito, E. Mayorga, Y. Niwa, P. A. Raymond, V. V. S. S. Sarma, and R. Lasco
Biogeosciences, 10, 513–527, https://doi.org/10.5194/bg-10-513-2013, https://doi.org/10.5194/bg-10-513-2013, 2013
T. Tanaka, S. Alliouane, R. G. B. Bellerby, J. Czerny, A. de Kluijver, U. Riebesell, K. G. Schulz, A. Silyakova, and J.-P. Gattuso
Biogeosciences, 10, 315–325, https://doi.org/10.5194/bg-10-315-2013, https://doi.org/10.5194/bg-10-315-2013, 2013
J. Piontek, C. Borchard, M. Sperling, K. G. Schulz, U. Riebesell, and A. Engel
Biogeosciences, 10, 297–314, https://doi.org/10.5194/bg-10-297-2013, https://doi.org/10.5194/bg-10-297-2013, 2013
M. Sperling, J. Piontek, G. Gerdts, A. Wichels, H. Schunck, A.-S. Roy, J. La Roche, J. Gilbert, J. I. Nissimov, L. Bittner, S. Romac, U. Riebesell, and A. Engel
Biogeosciences, 10, 181–191, https://doi.org/10.5194/bg-10-181-2013, https://doi.org/10.5194/bg-10-181-2013, 2013
K. G. Schulz, R. G. J. Bellerby, C. P. D. Brussaard, J. Büdenbender, J. Czerny, A. Engel, M. Fischer, S. Koch-Klavsen, S. A. Krug, S. Lischka, A. Ludwig, M. Meyerhöfer, G. Nondal, A. Silyakova, A. Stuhr, and U. Riebesell
Biogeosciences, 10, 161–180, https://doi.org/10.5194/bg-10-161-2013, https://doi.org/10.5194/bg-10-161-2013, 2013
W. Gülzow, G. Rehder, J. Schneider v. Deimling, T. Seifert, and Z. Tóth
Biogeosciences, 10, 81–99, https://doi.org/10.5194/bg-10-81-2013, https://doi.org/10.5194/bg-10-81-2013, 2013
Related subject area
Biogeochemistry: Open Ocean
Coccolithophore abundance and production and their impacts on particulate inorganic carbon cycling in the western North Pacific
A time series analysis of transparent exopolymer particle distributions and C : N stoichiometry in the subtropical North Pacific: a key process in net community production and preformed nitrate anomalies?
Marine snow morphology drives sinking and attenuation in the ocean interior
An upper-mesopelagic-zone carbon budget for the subarctic North Pacific
Relationships between the concentration of particulate organic nitrogen and the inherent optical properties of seawater in oceanic surface waters
Inadequacies in the representation of sub-seasonal phytoplankton dynamics in Earth system models
Nitrogen dynamics and nitrate stable isotopes indicate nitrogen loss in the Bay of Bengal
Interactions between ocean alkalinity enhancement and phytoplankton in an Earth System Model
A tracer study for the development of in-water monitoring, reporting, and verification (MRV) of ship-based ocean alkalinity enhancement
Composite model-based estimate of the ocean carbon sink from 1959 to 2022
Phytoplankton community structure in relation to iron and macronutrient fluxes from subsurface waters in the western North Pacific during summer
Intense and localized export of selected marine snow types at eddy edges in the South Atlantic Ocean
Spatial distributions of iron and manganese in surface waters of the Arctic's Laptev and East Siberian seas
Climate-driven shifts in Southern Ocean primary producers and biogeochemistry in CMIP6 models
Oceanic enrichment of ammonium and its impacts on phytoplankton community composition under a high-emissions scenario
Ocean acidification trends and carbonate system dynamics across the North Atlantic subpolar gyre water masses during 2009–2019
From small scale variability to mesoscale stability in surface ocean pH: implications for air-sea CO2 equilibration
Sedimentary organic matter signature hints at the phytoplankton-driven biological carbon pump in the central Arabian Sea
Hydrological cycle amplification imposes spatial patterns on the climate change response of ocean pH and carbonate chemistry
Assessing the tropical Atlantic biogeochemical processes in the Norwegian Earth System Model
Evolution of oxygen and stratification and their relationship in the North Pacific Ocean in CMIP6 Earth system models
Evaluation of CMIP6 model performance in simulating historical biogeochemistry across the southern South China Sea
Drivers of decadal trends in the ocean carbon sink in the past, present, and future in Earth system models
Anthropogenic carbon storage and its decadal changes in the Atlantic between 1990–2020
Ocean alkalinity enhancement impacts: regrowth of marine microalgae in alkaline mineral concentrations simulating the initial concentrations after ship-based dispersions
Climatic controls on metabolic constraints in the ocean
Effects of grain size and seawater salinity on magnesium hydroxide dissolution and secondary calcium carbonate precipitation kinetics: implications for ocean alkalinity enhancement
Short-term response of Emiliania huxleyi growth and morphology to abrupt salinity stress
Assessing the impact of CO2-equilibrated ocean alkalinity enhancement on microbial metabolic rates in an oligotrophic system
Phosphomonoesterase and phosphodiesterase activities in the eastern Mediterranean in two contrasting seasonal situations
Net primary production annual maxima in the North Atlantic projected to shift in the 21st century
Testing the influence of light on nitrite cycling in the eastern tropical North Pacific
Loss of nitrogen via anaerobic ammonium oxidation (anammox) in the California Current system during the late Quaternary
Technical note: Assessment of float pH data quality control methods – a case study in the subpolar northwest Atlantic Ocean
Linking northeastern North Pacific oxygen changes to upstream surface outcrop variations
Underestimation of multi-decadal global O2 loss due to an optimal interpolation method
Reviews and syntheses: expanding the global coverage of gross primary production and net community production measurements using Biogeochemical-Argo floats
Characteristics of surface physical and biogeochemical parameters within mesoscale eddies in the Southern Ocean
Seasonal dynamics and annual budget of dissolved inorganic carbon in the northwestern Mediterranean deep-convection region
The fingerprint of climate variability on the surface ocean cycling of iron and its isotopes
Reconstructing the ocean's mesopelagic zone carbon budget: sensitivity and estimation of parameters associated with prokaryotic remineralization
Seasonal cycles of biogeochemical fluxes in the Scotia Sea, Southern Ocean: a stable isotope approach
Absence of photophysiological response to iron addition in autumn phytoplankton in the Antarctic sea-ice zone
Optimal parameters for the ocean's nutrient, carbon, and oxygen cycles compensate for circulation biases but replumb the biological pump
Importance of multiple sources of iron for the upper-ocean biogeochemistry over the northern Indian Ocean
Exploring the role of different data types and timescales in the quality of marine biogeochemical model calibration
All about nitrite: exploring nitrite sources and sinks in the eastern tropical North Pacific oxygen minimum zone
Fossil coccolith morphological attributes as a new proxy for deep ocean carbonate chemistry
Reconstructing ocean carbon storage with CMIP6 Earth system models and synthetic Argo observations
Using machine learning and Biogeochemical-Argo (BGC-Argo) floats to assess biogeochemical models and optimize observing system design
Yuye Han, Zvi Steiner, Zhimian Cao, Di Fan, Junhui Chen, Jimin Yu, and Minhan Dai
Biogeosciences, 22, 3681–3697, https://doi.org/10.5194/bg-22-3681-2025, https://doi.org/10.5194/bg-22-3681-2025, 2025
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Our results suggest coccolithophore calcite accounts for a major fraction of PIC (particulate inorganic carbon) standing stocks in the western North Pacific, with a markedly higher contribution in the oligotrophic subtropical gyre than in the Kuroshio–Oyashio transition region, which highlights the importance of coccolithophores for PIC production in the pelagic ocean, particularly in oligotrophic ocean waters.
Kieran Curran, Tracy A. Villareal, and Robert T. Letscher
Biogeosciences, 22, 3515–3531, https://doi.org/10.5194/bg-22-3515-2025, https://doi.org/10.5194/bg-22-3515-2025, 2025
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This work provides a 2-year record of marine organic gel concentrations from an open-ocean site in the subtropical North Pacific Ocean north of Hawaii. These microscopic gels are investigated to understand their importance as an understudied component of organic matter cycling by marine microbes. We find an important role of gel cycling during the summer months, helping explain previously contradictory estimates of nutrient supply and demand for the subtropical ocean.
Yawouvi Dodji Soviadan, Miriam Beck, Joelle Habib, Alberto Baudena, Laetitia Drago, Alexandre Accardo, Remi Laxenaire, Sabrina Speich, Peter Brandt, Rainer Kiko, and Stemmann Lars
Biogeosciences, 22, 3485–3501, https://doi.org/10.5194/bg-22-3485-2025, https://doi.org/10.5194/bg-22-3485-2025, 2025
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Key parameters representing the gravity flux in global models are sinking speed and vertical attenuation of exported material. We calculate, for the first time, these parameters in situ in the ocean for six intermittent blooms followed by export events using high-resolution (3 d) time series of 0–1000 m depth profiles from imaging sensors mounted on an Argo float. We show that sinking speed depends not only on size but also on the morphology of the particles, with density being an important property.
Brandon M. Stephens, Montserrat Roca-Martí, Amy E. Maas, Vinícius J. Amaral, Samantha Clevenger, Shawnee Traylor, Claudia R. Benitez-Nelson, Philip W. Boyd, Ken O. Buesseler, Craig A. Carlson, Nicolas Cassar, Margaret Estapa, Andrea J. Fassbender, Yibin Huang, Phoebe J. Lam, Olivier Marchal, Susanne Menden-Deuer, Nicola L. Paul, Alyson E. Santoro, David A. Siegel, and David P. Nicholson
Biogeosciences, 22, 3301–3328, https://doi.org/10.5194/bg-22-3301-2025, https://doi.org/10.5194/bg-22-3301-2025, 2025
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The ocean’s mesopelagic zone (MZ) plays a crucial role in the global carbon cycle. This study combines new and previously published measurements of organic carbon supply and demand collected in August 2018 in the MZ of the subarctic North Pacific Ocean. Supply was insufficient to meet demand in August, but supply entering into the MZ in the spring of 2018 could have met the August demand. Results suggest observations over seasonal timescales may help to close MZ carbon budgets.
Alain Fumenia, Hubert Loisel, Rick A. Reynolds, and Dariusz Stramski
Biogeosciences, 22, 2461–2484, https://doi.org/10.5194/bg-22-2461-2025, https://doi.org/10.5194/bg-22-2461-2025, 2025
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Particulate organic nitrogen (PON) plays a central role in ocean biogeochemistry, yet limited in situ data hinder a full understanding of PON variability and associated processes. Measurements of optical properties offer an alternative for assessing PON across diverse marine environments. Our analysis reveals strong relationships between PON and optical properties, supporting a promising means to assess PON from optical measurements performed in situ or conducted from remote-sensing platforms.
Madhavan Girijakumari Keerthi, Olivier Aumont, Lester Kwiatkowski, and Marina Levy
Biogeosciences, 22, 2163–2180, https://doi.org/10.5194/bg-22-2163-2025, https://doi.org/10.5194/bg-22-2163-2025, 2025
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We assessed how well climate models replicate sub-seasonal changes in ocean chlorophyll observed by satellites. Models struggle to capture these variations accurately. Some overestimate fluctuations and their impact on annual chlorophyll variability, while others underestimate them. The underestimation is likely due to limited model resolution, while the overestimation may come from internal model oscillations.
Gesa Schulz, Kirstin Dähnke, Tina Sanders, Jan Penopp, Hermann W. Bange, Rena Czeschel, and Birgit Gaye
EGUsphere, https://doi.org/10.5194/egusphere-2025-1660, https://doi.org/10.5194/egusphere-2025-1660, 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 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.
Miriam Seifert, Christopher Danek, Christoph Völker, and Judith Hauck
EGUsphere, https://doi.org/10.5194/egusphere-2025-1495, https://doi.org/10.5194/egusphere-2025-1495, 2025
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Ocean alkalinity enhancement (OAE) can help to remove CO2 from the atmosphere. Yet, our study is the first that investigates the link between OAE and phytoplankton in an Earth System Model. We show that OAE can indirectly decrease primary production, and that biological feedbacks can modify the efficiency of OAE. Our study provides hints for ecological risks of OAE and the quantification of carbon drawdown, and can serve as a kick-start for other models to consider OAE-ecosystem interactions.
Adam V. Subhas, Jennie E. Rheuban, Zhaohui Aleck Wang, Daniel C. McCorkle, Anna P. M. Michel, Lukas Marx, Chloe L. Dean, Kate Morkeski, Matthew G. Hayden, Mary Burkitt-Gray, Francis Elder, Yiming Guo, Heather H. Kim, and Ke Chen
EGUsphere, https://doi.org/10.5194/egusphere-2025-1348, https://doi.org/10.5194/egusphere-2025-1348, 2025
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Ocean alkalinity enhancement (OAE) is a carbon removal approach in which alkaline materials are added to the marine environment, increasing the ocean's ability to store carbon dioxide. We conducted an open-water experiment releasing and tracking a fluorescent water tracer. Under the right conditions, in-water monitoring of OAE does appear to be possible. We conclude with a series of practical recommendations for open-water OAE monitoring.
Jens Terhaar
Biogeosciences, 22, 1631–1649, https://doi.org/10.5194/bg-22-1631-2025, https://doi.org/10.5194/bg-22-1631-2025, 2025
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The ocean is a major natural carbon sink. Despite its importance, estimates of the ocean carbon sink remain uncertain. Here, I present a hybrid model estimate of the ocean carbon sink from 1959 to 2022. By combining ocean models in hindcast mode and Earth system models, I keep the strength of each approach and remove the respective weaknesses. This composite model estimate is similar in magnitude to the best estimate of the Global Carbon Budget but 70 % less uncertain.
Huailin Deng, Koji Suzuki, Ichiro Yasuda, Hiroshi Ogawa, and Jun Nishioka
Biogeosciences, 22, 1495–1508, https://doi.org/10.5194/bg-22-1495-2025, https://doi.org/10.5194/bg-22-1495-2025, 2025
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Iron (Fe) and nitrate are vital for primary production in the North Pacific. Sedimentary Fe is carried by North Pacific Intermediate Water to the North Pacific, but the nutrient return path and its effect on phytoplankton are unclear. By combining Fe and macronutrient fluxes with phytoplankton composition, this study firstly revealed that Fe supply from the subsurface greatly controls diatom abundance and identified the nutrient return path in the subarctic gyre and Kuroshio–Oyashio transition area.
Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann
Biogeosciences, 22, 1183–1201, https://doi.org/10.5194/bg-22-1183-2025, https://doi.org/10.5194/bg-22-1183-2025, 2025
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The open ocean helps mitigate climate change by storing CO2 via the biological carbon pump (BCP), which involves processes like organic carbon production at the surface and transferring it to the deep ocean via various pathways. By deploying an autonomous platform, we found significant marine snow accumulation from the surface to the mesopelagic zone in frontal regions between eddies. We suggest that the coupling of hydrodynamics at eddy edges and biological activity may enhance this process.
Naoya Kanna, Kazutaka Tateyama, Takuji Waseda, Anna Timofeeva, Maria Papadimitraki, Laura Whitmore, Hajime Obata, Daiki Nomura, Hiroshi Ogawa, Youhei Yamashita, and Igor Polyakov
Biogeosciences, 22, 1057–1076, https://doi.org/10.5194/bg-22-1057-2025, https://doi.org/10.5194/bg-22-1057-2025, 2025
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This article presents data on iron and manganese, essential micronutrients for primary producers in the Arctic Laptev and East Siberian seas (LESS). There, observations were made through international cooperation with the Nansen and Amundsen Basin Observational System expedition during the late summer of 2021. The results from this study indicate that the major sources controlling the iron and manganese distributions on the LESS continental margins are river discharge and shelf sediment input.
Ben J. Fisher, Alex J. Poulton, Michael P. Meredith, Kimberlee Baldry, Oscar Schofield, and Sian F. Henley
Biogeosciences, 22, 975–994, https://doi.org/10.5194/bg-22-975-2025, https://doi.org/10.5194/bg-22-975-2025, 2025
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The Southern Ocean is a rapidly warming environment, with subsequent impacts on ecosystems and biogeochemical cycling. This study examines changes in phytoplankton and biogeochemistry using a range of climate models. Under climate change, the Southern Ocean will be warmer, more acidic and more productive and will have reduced nutrient availability by 2100. However, there is substantial variability between models across key productivity parameters. We propose ways of reducing this uncertainty.
Pearse J. Buchanan, Juan J. Pierella Karlusich, Robyn E. Tuerena, Roxana Shafiee, E. Malcolm S. Woodward, Chris Bowler, and Alessandro Tagliabue
EGUsphere, https://doi.org/10.5194/egusphere-2024-3639, https://doi.org/10.5194/egusphere-2024-3639, 2025
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Ammonium is a form of nitrogen that may become more important for growth of marine primary producers (i.e., phytoplankton) in the future. Because some phytoplankton taxa have a greater affinity for ammonium than others, the relative increase in ammonium could cause shifts in community composition. We quantify ammonium enrichment, identify its drivers, and isolate the possible effect on phytoplankton community composition under a high emissions scenario.
David Curbelo-Hernández, Fiz F. Pérez, Melchor González-Dávila, Sergey V. Gladyshev, Aridane G. González, David González-Santana, Antón Velo, Alexey Sokov, and J. Magdalena Santana-Casiano
Biogeosciences, 21, 5561–5589, https://doi.org/10.5194/bg-21-5561-2024, https://doi.org/10.5194/bg-21-5561-2024, 2024
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The study evaluated CO2–carbonate system dynamics in the North Atlantic subpolar gyre during 2009–2019. Significant ocean acidification, largely due to rising anthropogenic CO2 levels, was found. Cooling, freshening, and enhanced convective processes intensified this trend, affecting calcite and aragonite saturation. The findings contribute to a deeper understanding of ocean acidification and improve our knowledge about its impact on marine ecosystems.
Louise Delaigue, Gert-Jan Reichart, Chris Galley, Yasmina Ourradi, and Matthew Paul Humphreys
EGUsphere, https://doi.org/10.5194/egusphere-2024-2853, https://doi.org/10.5194/egusphere-2024-2853, 2024
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Our study analyzed pH in ocean surface waters to understand how they fluctuate with changes in temperature, salinity, and biological activities. We found that temperature mainly controls daily pH variations, but biological processes also play a role, especially in affecting CO2 levels between the ocean and atmosphere. Our research shows how these factors together maintain the balance of ocean chemistry, which is crucial for predicting changes in marine environments.
Medhavi Pandey, Haimanti Biswas, Daniel Birgel, Nicole Burdanowitz, and Birgit Gaye
Biogeosciences, 21, 4681–4698, https://doi.org/10.5194/bg-21-4681-2024, https://doi.org/10.5194/bg-21-4681-2024, 2024
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We analysed sea surface temperature (SST) proxy and plankton biomarkers in sediments that accumulate sinking material signatures from surface waters in the central Arabian Sea (21°–11° N, 64° E), a tropical basin impacted by monsoons. We saw a north–south SST gradient, and the biological proxies showed more organic matter from larger algae in the north. Smaller algae and zooplankton were more numerous in the south. These trends were related to ocean–atmospheric processes and oxygen availability.
Allison Hogikyan and Laure Resplandy
Biogeosciences, 21, 4621–4636, https://doi.org/10.5194/bg-21-4621-2024, https://doi.org/10.5194/bg-21-4621-2024, 2024
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Rising atmospheric CO2 influences ocean carbon chemistry, leading to ocean acidification. Global warming introduces spatial patterns in the intensity of ocean acidification. We show that the most prominent spatial patterns are controlled by warming-driven changes in rainfall and evaporation, not by the direct effect of warming on carbon chemistry and pH. These evaporation and rainfall patterns oppose acidification in saltier parts of the ocean and enhance acidification in fresher regions.
Shunya Koseki, Lander R. Crespo, Jerry Tjiputra, Filippa Fransner, Noel S. Keenlyside, and David Rivas
Biogeosciences, 21, 4149–4168, https://doi.org/10.5194/bg-21-4149-2024, https://doi.org/10.5194/bg-21-4149-2024, 2024
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We investigated how the physical biases of an Earth system model influence the marine biogeochemical processes in the tropical Atlantic. With four different configurations of the model, we have shown that the versions with better SST reproduction tend to better represent the primary production and air–sea CO2 flux in terms of climatology, seasonal cycle, and response to climate variability.
Lyuba Novi, Annalisa Bracco, Takamitsu Ito, and Yohei Takano
Biogeosciences, 21, 3985–4005, https://doi.org/10.5194/bg-21-3985-2024, https://doi.org/10.5194/bg-21-3985-2024, 2024
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We explored the relationship between oxygen and stratification in the North Pacific Ocean using a combination of data mining and machine learning. We used isopycnic potential vorticity (IPV) as an indicator to quantify ocean ventilation and analyzed its predictability, a strong O2–IPV connection, and predictability for IPV in the tropical Pacific. This opens new routes for monitoring ocean O2 through few observational sites co-located with more abundant IPV measurements in the tropical Pacific.
Winfred Marshal, Jing Xiang Chung, Nur Hidayah Roseli, Roswati Md Amin, and Mohd Fadzil Bin Mohd Akhir
Biogeosciences, 21, 4007–4035, https://doi.org/10.5194/bg-21-4007-2024, https://doi.org/10.5194/bg-21-4007-2024, 2024
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This study stands out for thoroughly examining CMIP6 ESMs' ability to simulate biogeochemical variables in the southern South China Sea, an economically important region. It assesses variables like chlorophyll, phytoplankton, nitrate, and oxygen on annual and seasonal scales. While global assessments exist, this study addresses a gap by objectively ranking 13 CMIP6 ocean biogeochemistry models' performance at a regional level, focusing on replicating specific observed biogeochemical variables.
Jens Terhaar
Biogeosciences, 21, 3903–3926, https://doi.org/10.5194/bg-21-3903-2024, https://doi.org/10.5194/bg-21-3903-2024, 2024
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Despite the ocean’s importance in the carbon cycle and hence the climate, observing the ocean carbon sink remains challenging. Here, I use an ensemble of 12 models to understand drivers of decadal trends of the past, present, and future ocean carbon sink. I show that 80 % of the decadal trends in the multi-model mean ocean carbon sink can be explained by changes in decadal trends in atmospheric CO2. The remaining 20 % are due to internal climate variability and ocean heat uptake.
Reiner Steinfeldt, Monika Rhein, and Dagmar Kieke
Biogeosciences, 21, 3839–3867, https://doi.org/10.5194/bg-21-3839-2024, https://doi.org/10.5194/bg-21-3839-2024, 2024
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We calculate the amount of anthropogenic carbon (Cant) in the Atlantic for the years 1990, 2000, 2010 and 2020. Cant is the carbon that is taken up by the ocean as a result of humanmade CO2 emissions. To determine the amount of Cant, we apply a technique that is based on the observations of other humanmade gases (e.g., chlorofluorocarbons). Regionally, changes in ocean ventilation have an impact on the storage of Cant. Overall, the increase in Cant is driven by the rising CO2 in the atmosphere.
Stephanie Delacroix, Tor Jensen Nystuen, August E. Dessen Tobiesen, Andrew L. King, and Erik Höglund
Biogeosciences, 21, 3677–3690, https://doi.org/10.5194/bg-21-3677-2024, https://doi.org/10.5194/bg-21-3677-2024, 2024
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The addition of alkaline minerals into the ocean might reduce excessive anthropogenic CO2 emissions. Magnesium hydroxide can be added in large amounts because of its low seawater solubility without reaching harmful pH levels. The toxicity effect results of magnesium hydroxide, by simulating the expected concentrations from a ship's dispersion scenario, demonstrated low impacts on both sensitive and local assemblages of marine microalgae when compared to calcium hydroxide.
Precious Mongwe, Matthew Long, Takamitsu Ito, Curtis Deutsch, and Yeray Santana-Falcón
Biogeosciences, 21, 3477–3490, https://doi.org/10.5194/bg-21-3477-2024, https://doi.org/10.5194/bg-21-3477-2024, 2024
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We use a collection of measurements that capture the physiological sensitivity of organisms to temperature and oxygen and a CESM1 large ensemble to investigate how natural climate variations and climate warming will impact the ability of marine heterotrophic marine organisms to support habitats in the future. We find that warming and dissolved oxygen loss over the next several decades will reduce the volume of ocean habitats and will increase organisms' vulnerability to extremes.
Charly A. Moras, Tyler Cyronak, Lennart T. Bach, Renaud Joannes-Boyau, and Kai G. Schulz
Biogeosciences, 21, 3463–3475, https://doi.org/10.5194/bg-21-3463-2024, https://doi.org/10.5194/bg-21-3463-2024, 2024
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We investigate the effects of mineral grain size and seawater salinity on magnesium hydroxide dissolution and calcium carbonate precipitation kinetics for ocean alkalinity enhancement. Salinity did not affect the dissolution, but calcium carbonate formed earlier at lower salinities due to the lower magnesium and dissolved organic carbon concentrations. Smaller grain sizes dissolved faster but calcium carbonate precipitated earlier, suggesting that medium grain sizes are optimal for kinetics.
Rosie M. Sheward, Christina Gebühr, Jörg Bollmann, and Jens O. Herrle
Biogeosciences, 21, 3121–3141, https://doi.org/10.5194/bg-21-3121-2024, https://doi.org/10.5194/bg-21-3121-2024, 2024
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How quickly do marine microorganisms respond to salinity stress? Our experiments with the calcifying marine plankton Emiliania huxleyi show that growth and cell morphology responded to salinity stress within as little as 24–48 hours, demonstrating that morphology and calcification are sensitive to salinity over a range of timescales. Our results have implications for understanding the short-term role of E. huxleyi in biogeochemical cycles and in size-based paleoproxies for salinity.
Laura Marín-Samper, Javier Arístegui, Nauzet Hernández-Hernández, Joaquín Ortiz, Stephen D. Archer, Andrea Ludwig, and Ulf Riebesell
Biogeosciences, 21, 2859–2876, https://doi.org/10.5194/bg-21-2859-2024, https://doi.org/10.5194/bg-21-2859-2024, 2024
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Our planet is facing a climate crisis. Scientists are working on innovative solutions that will aid in capturing the hard to abate emissions before it is too late. Exciting research reveals that ocean alkalinity enhancement, a key climate change mitigation strategy, does not harm phytoplankton, the cornerstone of marine ecosystems. Through meticulous study, we may have uncovered a positive relationship: up to a specific limit, enhancing ocean alkalinity boosts photosynthesis by certain species.
France Van Wambeke, Pascal Conan, Mireille Pujo-Pay, Vincent Taillandier, Olivier Crispi, Alexandra Pavlidou, Sandra Nunige, Morgane Didry, Christophe Salmeron, and Elvira Pulido-Villena
Biogeosciences, 21, 2621–2640, https://doi.org/10.5194/bg-21-2621-2024, https://doi.org/10.5194/bg-21-2621-2024, 2024
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Phosphomonoesterase (PME) and phosphodiesterase (PDE) activities over the epipelagic zone are described in the eastern Mediterranean Sea in winter and autumn. The types of concentration kinetics obtained for PDE (saturation at 50 µM, high Km, high turnover times) compared to those of PME (saturation at 1 µM, low Km, low turnover times) are discussed in regard to the possible inequal distribution of PDE and PME in the size continuum of organic material and accessibility to phosphodiesters.
Jenny Hieronymus, Magnus Hieronymus, Matthias Gröger, Jörg Schwinger, Raffaele Bernadello, Etienne Tourigny, Valentina Sicardi, Itzel Ruvalcaba Baroni, and Klaus Wyser
Biogeosciences, 21, 2189–2206, https://doi.org/10.5194/bg-21-2189-2024, https://doi.org/10.5194/bg-21-2189-2024, 2024
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The timing of the net primary production annual maxima in the North Atlantic in the period 1750–2100 is investigated using two Earth system models and the high-emissions scenario SSP5-8.5. It is found that, for most of the region, the annual maxima occur progressively earlier, with the most change occurring after the year 2000. Shifts in the seasonality of the primary production may impact the entire ecosystem, which highlights the need for long-term monitoring campaigns in this area.
Nicole M. Travis, Colette L. Kelly, and Karen L. Casciotti
Biogeosciences, 21, 1985–2004, https://doi.org/10.5194/bg-21-1985-2024, https://doi.org/10.5194/bg-21-1985-2024, 2024
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We conducted experimental manipulations of light level on microbial communities from the primary nitrite maximum. Overall, while individual microbial processes have different directions and magnitudes in their response to increasing light, the net community response is a decline in nitrite production with increasing light. We conclude that while increased light may decrease net nitrite production, high-light conditions alone do not exclude nitrification from occurring in the surface ocean.
Zoë Rebecca van Kemenade, Zeynep Erdem, Ellen Christine Hopmans, Jaap Smede Sinninghe Damsté, and Darci Rush
Biogeosciences, 21, 1517–1532, https://doi.org/10.5194/bg-21-1517-2024, https://doi.org/10.5194/bg-21-1517-2024, 2024
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The California Current system (CCS) hosts the eastern subtropical North Pacific oxygen minimum zone (ESTNP OMZ). This study shows anaerobic ammonium oxidizing (anammox) bacteria cause a loss of bioavailable nitrogen (N) in the ESTNP OMZ throughout the late Quaternary. Anammox occurred during both glacial and interglacial periods and was driven by the supply of organic matter and changes in ocean currents. These findings may have important consequences for biogeochemical models of the CCS.
Cathy Wimart-Rousseau, Tobias Steinhoff, Birgit Klein, Henry Bittig, and Arne Körtzinger
Biogeosciences, 21, 1191–1211, https://doi.org/10.5194/bg-21-1191-2024, https://doi.org/10.5194/bg-21-1191-2024, 2024
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The marine CO2 system can be measured independently and continuously by BGC-Argo floats since numerous pH sensors have been developed to suit these autonomous measurements platforms. By applying the Argo correction routines to float pH data acquired in the subpolar North Atlantic Ocean, we report the uncertainty and lack of objective criteria associated with the choice of the reference method as well the reference depth for the pH correction.
Sabine Mecking and Kyla Drushka
Biogeosciences, 21, 1117–1133, https://doi.org/10.5194/bg-21-1117-2024, https://doi.org/10.5194/bg-21-1117-2024, 2024
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This study investigates whether northeastern North Pacific oxygen changes may be caused by surface density changes in the northwest as water moves along density horizons from the surface into the subsurface ocean. A correlation is found with a lag that about matches the travel time of water from the northwest to the northeast. Salinity is the main driver causing decadal changes in surface density, whereas salinity and temperature contribute about equally to long-term declining density trends.
Takamitsu Ito, Hernan E. Garcia, Zhankun Wang, Shoshiro Minobe, Matthew C. Long, Just Cebrian, James Reagan, Tim Boyer, Christopher Paver, Courtney Bouchard, Yohei Takano, Seth Bushinsky, Ahron Cervania, and Curtis A. Deutsch
Biogeosciences, 21, 747–759, https://doi.org/10.5194/bg-21-747-2024, https://doi.org/10.5194/bg-21-747-2024, 2024
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This study aims to estimate how much oceanic oxygen has been lost and its uncertainties. One major source of uncertainty comes from the statistical gap-filling methods. Outputs from Earth system models are used to generate synthetic observations where oxygen data are extracted from the model output at the location and time of historical oceanographic cruises. Reconstructed oxygen trend is approximately two-thirds of the true trend.
Robert W. Izett, Katja Fennel, Adam C. Stoer, and David P. Nicholson
Biogeosciences, 21, 13–47, https://doi.org/10.5194/bg-21-13-2024, https://doi.org/10.5194/bg-21-13-2024, 2024
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This paper provides an overview of the capacity to expand the global coverage of marine primary production estimates using autonomous ocean-going instruments, called Biogeochemical-Argo floats. We review existing approaches to quantifying primary production using floats, provide examples of the current implementation of the methods, and offer insights into how they can be better exploited. This paper is timely, given the ongoing expansion of the Biogeochemical-Argo array.
Qian Liu, Yingjie Liu, and Xiaofeng Li
Biogeosciences, 20, 4857–4874, https://doi.org/10.5194/bg-20-4857-2023, https://doi.org/10.5194/bg-20-4857-2023, 2023
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In the Southern Ocean, abundant eddies behave opposite to our expectations. That is, anticyclonic (cyclonic) eddies are cold (warm). By investigating the variations of physical and biochemical parameters in eddies, we find that abnormal eddies have unique and significant effects on modulating the parameters. This study fills a gap in understanding the effects of abnormal eddies on physical and biochemical parameters in the Southern Ocean.
Caroline Ulses, Claude Estournel, Patrick Marsaleix, Karline Soetaert, Marine Fourrier, Laurent Coppola, Dominique Lefèvre, Franck Touratier, Catherine Goyet, Véronique Guglielmi, Fayçal Kessouri, Pierre Testor, and Xavier Durrieu de Madron
Biogeosciences, 20, 4683–4710, https://doi.org/10.5194/bg-20-4683-2023, https://doi.org/10.5194/bg-20-4683-2023, 2023
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Deep convection plays a key role in the circulation, thermodynamics, and biogeochemical cycles in the Mediterranean Sea, considered to be a hotspot of biodiversity and climate change. In this study, we investigate the seasonal and annual budget of dissolved inorganic carbon in the deep-convection area of the northwestern Mediterranean Sea.
Daniela König and Alessandro Tagliabue
Biogeosciences, 20, 4197–4212, https://doi.org/10.5194/bg-20-4197-2023, https://doi.org/10.5194/bg-20-4197-2023, 2023
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Using model simulations, we show that natural and anthropogenic changes in the global climate leave a distinct fingerprint in the isotopic signatures of iron in the surface ocean. We find that these climate effects on iron isotopes are often caused by the redistribution of iron from different external sources to the ocean, due to changes in ocean currents, and by changes in algal growth, which take up iron. Thus, isotopes may help detect climate-induced changes in iron supply and algal uptake.
Chloé Baumas, Robin Fuchs, Marc Garel, Jean-Christophe Poggiale, Laurent Memery, Frédéric A. C. Le Moigne, and Christian Tamburini
Biogeosciences, 20, 4165–4182, https://doi.org/10.5194/bg-20-4165-2023, https://doi.org/10.5194/bg-20-4165-2023, 2023
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Through the sink of particles in the ocean, carbon (C) is exported and sequestered when reaching 1000 m. Attempts to quantify C exported vs. C consumed by heterotrophs have increased. Yet most of the conducted estimations have led to C demands several times higher than C export. The choice of parameters greatly impacts the results. As theses parameters are overlooked, non-accurate values are often used. In this study we show that C budgets can be well balanced when using appropriate values.
Anna Belcher, Sian F. Henley, Katharine Hendry, Marianne Wootton, Lisa Friberg, Ursula Dallman, Tong Wang, Christopher Coath, and Clara Manno
Biogeosciences, 20, 3573–3591, https://doi.org/10.5194/bg-20-3573-2023, https://doi.org/10.5194/bg-20-3573-2023, 2023
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The oceans play a crucial role in the uptake of atmospheric carbon dioxide, particularly the Southern Ocean. The biological pumping of carbon from the surface to the deep ocean is key to this. Using sediment trap samples from the Scotia Sea, we examine biogeochemical fluxes of carbon, nitrogen, and biogenic silica and their stable isotope compositions. We find phytoplankton community structure and physically mediated processes are important controls on particulate fluxes to the deep ocean.
Asmita Singh, Susanne Fietz, Sandy J. Thomalla, Nicolas Sanchez, Murat V. Ardelan, Sébastien Moreau, Hanna M. Kauko, Agneta Fransson, Melissa Chierici, Saumik Samanta, Thato N. Mtshali, Alakendra N. Roychoudhury, and Thomas J. Ryan-Keogh
Biogeosciences, 20, 3073–3091, https://doi.org/10.5194/bg-20-3073-2023, https://doi.org/10.5194/bg-20-3073-2023, 2023
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Despite the scarcity of iron in the Southern Ocean, seasonal blooms occur due to changes in nutrient and light availability. Surprisingly, during an autumn bloom in the Antarctic sea-ice zone, the results from incubation experiments showed no significant photophysiological response of phytoplankton to iron addition. This suggests that ambient iron concentrations were sufficient, challenging the notion of iron deficiency in the Southern Ocean through extended iron-replete post-bloom conditions.
Benoît Pasquier, Mark Holzer, Matthew A. Chamberlain, Richard J. Matear, Nathaniel L. Bindoff, and François W. Primeau
Biogeosciences, 20, 2985–3009, https://doi.org/10.5194/bg-20-2985-2023, https://doi.org/10.5194/bg-20-2985-2023, 2023
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Modeling the ocean's carbon and oxygen cycles accurately is challenging. Parameter optimization improves the fit to observed tracers but can introduce artifacts in the biological pump. Organic-matter production and subsurface remineralization rates adjust to compensate for circulation biases, changing the pathways and timescales with which nutrients return to the surface. Circulation biases can thus strongly alter the system’s response to ecological change, even when parameters are optimized.
Priyanka Banerjee
Biogeosciences, 20, 2613–2643, https://doi.org/10.5194/bg-20-2613-2023, https://doi.org/10.5194/bg-20-2613-2023, 2023
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This study shows that atmospheric deposition is the most important source of iron to the upper northern Indian Ocean for phytoplankton growth. This is followed by iron from continental-shelf sediment. Phytoplankton increase following iron addition is possible only with high background levels of nitrate. Vertical mixing is the most important physical process supplying iron to the upper ocean in this region throughout the year. The importance of ocean currents in supplying iron varies seasonally.
Iris Kriest, Julia Getzlaff, Angela Landolfi, Volkmar Sauerland, Markus Schartau, and Andreas Oschlies
Biogeosciences, 20, 2645–2669, https://doi.org/10.5194/bg-20-2645-2023, https://doi.org/10.5194/bg-20-2645-2023, 2023
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Global biogeochemical ocean models are often subjectively assessed and tuned against observations. We applied different strategies to calibrate a global model against observations. Although the calibrated models show similar tracer distributions at the surface, they differ in global biogeochemical fluxes, especially in global particle flux. Simulated global volume of oxygen minimum zones varies strongly with calibration strategy and over time, rendering its temporal extrapolation difficult.
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.
Amanda Gerotto, Hongrui Zhang, Renata Hanae Nagai, Heather M. Stoll, Rubens César Lopes Figueira, Chuanlian Liu, and Iván Hernández-Almeida
Biogeosciences, 20, 1725–1739, https://doi.org/10.5194/bg-20-1725-2023, https://doi.org/10.5194/bg-20-1725-2023, 2023
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Based on the analysis of the response of coccolithophores’ morphological attributes in a laboratory dissolution experiment and surface sediment samples from the South China Sea, we proposed that the thickness shape (ks) factor of fossil coccoliths together with the normalized ks variation, which is the ratio of the standard deviation of ks (σ) over the mean ks (σ/ks), is a robust and novel proxy to reconstruct past changes in deep ocean carbon chemistry.
Katherine E. Turner, Doug M. Smith, Anna Katavouta, and Richard G. Williams
Biogeosciences, 20, 1671–1690, https://doi.org/10.5194/bg-20-1671-2023, https://doi.org/10.5194/bg-20-1671-2023, 2023
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We present a new method for reconstructing ocean carbon using climate models and temperature and salinity observations. To test this method, we reconstruct modelled carbon using synthetic observations consistent with current sampling programmes. Sensitivity tests show skill in reconstructing carbon trends and variability within the upper 2000 m. Our results indicate that this method can be used for a new global estimate for ocean carbon content.
Alexandre Mignot, Hervé Claustre, Gianpiero Cossarini, Fabrizio D'Ortenzio, Elodie Gutknecht, Julien Lamouroux, Paolo Lazzari, Coralie Perruche, Stefano Salon, Raphaëlle Sauzède, Vincent Taillandier, and Anna Teruzzi
Biogeosciences, 20, 1405–1422, https://doi.org/10.5194/bg-20-1405-2023, https://doi.org/10.5194/bg-20-1405-2023, 2023
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Numerical models of ocean biogeochemistry are becoming a major tool to detect and predict the impact of climate change on marine resources and monitor ocean health. Here, we demonstrate the use of the global array of BGC-Argo floats for the assessment of biogeochemical models. We first detail the handling of the BGC-Argo data set for model assessment purposes. We then present 23 assessment metrics to quantify the consistency of BGC model simulations with respect to BGC-Argo data.
Cited articles
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Ferderer, A., Chase, Z., Kennedy, F., Schulz, K. G., and Bach, L. T.: Assessing the influence of ocean alkalinity enhancement on a coastal phytoplankton community, Biogeosciences, 19, 5375–5399, https://doi.org/10.5194/bg-19-5375-2022, 2022.
Ferderer, A., Schulz, K. G., Riebesell, U., Baker, K. G., Chase, Z., and Bach, L. T.: Investigating the effect of silicate- and calcium-based ocean alkalinity enhancement on diatom silicification, Biogeosciences, 21, 2777–2794, https://doi.org/10.5194/bg-21-2777-2024, 2024.
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Short summary
Ocean alkalinity enhancement (OAE) is being assessed for its potential to absorb atmospheric CO2 and store it for a long time. OAE still needs comprehensive assessment of its safety and effectiveness. We studied an idealised OAE application in a natural low-nutrient ecosystem over 1 month. Our results showed that biogeochemical functioning remained mostly stable but that the long-term capability for storing carbon may be limited at high alkalinity concentration.
Ocean alkalinity enhancement (OAE) is being assessed for its potential to absorb atmospheric CO2...
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