Articles | Volume 2-oae2023
https://doi.org/10.5194/sp-2-oae2023-2-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/sp-2-oae2023-2-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
27 Nov 2023
| OAE Guide 2023 | Chapter 2
| 27 Nov 2023 | OAE Guide 2023 | Chapter 2
Seawater carbonate chemistry considerations for ocean alkalinity enhancement research: theory, measurements, and calculations
Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia
Lennart T. Bach
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
Andrew G. Dickson
Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
Related authors
Falilu Adekunbi, Michaël Grelaud, Gerald Langer, Lucian Chukwu, Marta Álvarez, Shakirudeen Odunuga, Kai George Schulz, and Patrizia Ziveri
EGUsphere, https://doi.org/10.5194/egusphere-2025-3201, https://doi.org/10.5194/egusphere-2025-3201, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
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This study is the first to explore seasonal changes in coccolithophores, microscopic algae important for ocean life and the carbon cycle, off the coast of Nigeria. Their abundance and diversity increased during the rainy season, driven by shifts in the Intertropical Convergence Zone. Despite regional differences, these coastal communities show patterns similar to other parts of the world, revealing possible shared environmental pressures.
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.
Lennart Thomas Bach, Aaron James Ferderer, Julie LaRoche, and Kai Georg Schulz
Biogeosciences, 21, 3665–3676, https://doi.org/10.5194/bg-21-3665-2024, https://doi.org/10.5194/bg-21-3665-2024, 2024
Short summary
Short summary
Ocean alkalinity enhancement (OAE) is an emerging marine CO2 removal method, but its environmental effects are insufficiently understood. The OAE Pelagic Impact Intercomparison Project (OAEPIIP) provides funding for a standardized and globally replicated microcosm experiment to study the effects of OAE on plankton communities. Here, we provide a detailed manual for the OAEPIIP experiment. We expect OAEPIIP to help build scientific consensus on the effects of OAE on plankton.
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
Short summary
Short summary
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.
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
Short summary
Short summary
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.
Aaron Ferderer, Zanna Chase, Fraser Kennedy, Kai G. Schulz, and Lennart T. Bach
Biogeosciences, 19, 5375–5399, https://doi.org/10.5194/bg-19-5375-2022, https://doi.org/10.5194/bg-19-5375-2022, 2022
Short summary
Short summary
Ocean alkalinity enhancement has the capacity to remove vast quantities of carbon from the atmosphere, but its effect on marine ecosystems is largely unknown. We assessed the effect of increased alkalinity on a coastal phytoplankton community when seawater was equilibrated and not equilibrated with atmospheric CO2. We found that the phytoplankton community was moderately affected by increased alkalinity and equilibration with atmospheric CO2 had little influence on this effect.
Charly A. Moras, Lennart T. Bach, Tyler Cyronak, Renaud Joannes-Boyau, and Kai G. Schulz
Biogeosciences, 19, 3537–3557, https://doi.org/10.5194/bg-19-3537-2022, https://doi.org/10.5194/bg-19-3537-2022, 2022
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This research presents the first laboratory results of quick and hydrated lime dissolution in natural seawater. These two minerals are of great interest for ocean alkalinity enhancement, a strategy aiming to decrease atmospheric CO2 concentrations. Following the dissolution of these minerals, we identified several hurdles and presented ways to avoid them or completely negate them. Finally, we proceeded to various simulations in today’s oceans to implement the strategy at its highest potential.
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
Short summary
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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.
Michelle N. Simone, Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre
Biogeosciences, 18, 1823–1838, https://doi.org/10.5194/bg-18-1823-2021, https://doi.org/10.5194/bg-18-1823-2021, 2021
Short summary
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Estuaries are responsible for a large contribution of dissolved organic carbon (DOC) to the global C cycle, but it is unknown how this will change in the future. DOC fluxes from unvegetated sediments were investigated ex situ subject to conditions of warming and ocean acidification. The future climate shifted sediment fluxes from a slight DOC source to a significant sink, with global coastal DOC export decreasing by 80 %. This has global implications for C cycling and long-term C storage.
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
Short summary
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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.
Falilu Adekunbi, Michaël Grelaud, Gerald Langer, Lucian Chukwu, Marta Álvarez, Shakirudeen Odunuga, Kai George Schulz, and Patrizia Ziveri
EGUsphere, https://doi.org/10.5194/egusphere-2025-3201, https://doi.org/10.5194/egusphere-2025-3201, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
This study is the first to explore seasonal changes in coccolithophores, microscopic algae important for ocean life and the carbon cycle, off the coast of Nigeria. Their abundance and diversity increased during the rainy season, driven by shifts in the Intertropical Convergence Zone. Despite regional differences, these coastal communities show patterns similar to other parts of the world, revealing possible shared environmental pressures.
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
Short summary
Short summary
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.
Nina Bednaršek, Hanna van de Mortel, Greg Pelletier, Marisol García-Reyes, Richard A. Feely, and Andrew G. Dickson
Biogeosciences, 22, 473–498, https://doi.org/10.5194/bg-22-473-2025, https://doi.org/10.5194/bg-22-473-2025, 2025
Short summary
Short summary
The environmental impacts of ocean alkalinity enhancement (OAE) are unknown. Our synthesis, based on 68 collected studies with 84 unique species, shows that 35 % of species respond positively, 26 % respond negatively, and 39 % show a neutral response to alkalinity addition. Biological thresholds were found from 50 to 500 µmol kg−1 NaOH addition. A precautionary approach is warranted to avoid potential risks, while current regulatory framework needs improvements to assure safe biological limits.
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.
Lennart Thomas Bach, Aaron James Ferderer, Julie LaRoche, and Kai Georg Schulz
Biogeosciences, 21, 3665–3676, https://doi.org/10.5194/bg-21-3665-2024, https://doi.org/10.5194/bg-21-3665-2024, 2024
Short summary
Short summary
Ocean alkalinity enhancement (OAE) is an emerging marine CO2 removal method, but its environmental effects are insufficiently understood. The OAE Pelagic Impact Intercomparison Project (OAEPIIP) provides funding for a standardized and globally replicated microcosm experiment to study the effects of OAE on plankton communities. Here, we provide a detailed manual for the OAEPIIP experiment. We expect OAEPIIP to help build scientific consensus on the effects of OAE on plankton.
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
Short summary
Short summary
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.
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
Short summary
Short summary
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.
Jiaying A. Guo, Robert F. Strzepek, Kerrie M. Swadling, Ashley T. Townsend, and Lennart T. Bach
Biogeosciences, 21, 2335–2354, https://doi.org/10.5194/bg-21-2335-2024, https://doi.org/10.5194/bg-21-2335-2024, 2024
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Ocean alkalinity enhancement aims to increase atmospheric CO2 sequestration by adding alkaline materials to the ocean. We assessed the environmental effects of olivine and steel slag powder on coastal plankton. Overall, slag is more efficient than olivine in releasing total alkalinity and, thus, in its ability to sequester CO2. Slag also had less environmental effect on the enclosed plankton communities when considering its higher CO2 removal potential based on this 3-week experiment.
Lennart Thomas Bach
Biogeosciences, 21, 261–277, https://doi.org/10.5194/bg-21-261-2024, https://doi.org/10.5194/bg-21-261-2024, 2024
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Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method. OAE aims to accelerate chemical rock weathering, which is a natural process that slowly sequesters atmospheric carbon dioxide. This study shows that the addition of anthropogenic alkalinity via OAE can reduce the natural release of alkalinity and, therefore, reduce the efficiency of OAE for climate mitigation. However, the additionality problem could be mitigated via a variety of activities.
David T. Ho, Laurent Bopp, Jaime B. Palter, Matthew C. Long, Philip W. Boyd, Griet Neukermans, and Lennart T. Bach
State Planet, 2-oae2023, 12, https://doi.org/10.5194/sp-2-oae2023-12-2023, https://doi.org/10.5194/sp-2-oae2023-12-2023, 2023
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Monitoring, reporting, and verification (MRV) refers to the multistep process to quantify the amount of carbon dioxide removed by a carbon dioxide removal (CDR) activity. Here, we make recommendations for MRV for Ocean Alkalinity Enhancement (OAE) research, arguing that it has an obligation for comprehensiveness, reproducibility, and transparency, as it may become the foundation for assessing large-scale deployment. Both observations and numerical simulations will be needed for MRV.
Tyler Cyronak, Rebecca Albright, and Lennart T. Bach
State Planet, 2-oae2023, 7, https://doi.org/10.5194/sp-2-oae2023-7-2023, https://doi.org/10.5194/sp-2-oae2023-7-2023, 2023
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Ocean alkalinity enhancement (OAE) is a marine carbon dioxide removal (CDR) approach. Publicly funded research projects have begun, and philanthropic funding and start-ups are collectively pushing the field forward. This rapid progress in research activities has created an urgent need to learn if and how OAE can work at scale. This chapter of the Guide to Best Practices in Ocean Alkalinity Enhancement Research focuses on field experiments.
Andreas Oschlies, Lennart T. Bach, Rosalind E. M. Rickaby, Terre Satterfield, Romany Webb, and Jean-Pierre Gattuso
State Planet, 2-oae2023, 1, https://doi.org/10.5194/sp-2-oae2023-1-2023, https://doi.org/10.5194/sp-2-oae2023-1-2023, 2023
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Reaching promised climate targets will require the deployment of carbon dioxide removal (CDR). Marine CDR options receive more and more interest. Based on idealized theoretical studies, ocean alkalinity enhancement (OAE) appears as a promising marine CDR method. We provide an overview on the current situation of developing OAE as a marine CDR method and describe the history that has led to the creation of the OAE research best practice guide.
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.
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.
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.
Aaron Ferderer, Zanna Chase, Fraser Kennedy, Kai G. Schulz, and Lennart T. Bach
Biogeosciences, 19, 5375–5399, https://doi.org/10.5194/bg-19-5375-2022, https://doi.org/10.5194/bg-19-5375-2022, 2022
Short summary
Short summary
Ocean alkalinity enhancement has the capacity to remove vast quantities of carbon from the atmosphere, but its effect on marine ecosystems is largely unknown. We assessed the effect of increased alkalinity on a coastal phytoplankton community when seawater was equilibrated and not equilibrated with atmospheric CO2. We found that the phytoplankton community was moderately affected by increased alkalinity and equilibration with atmospheric CO2 had little influence on this effect.
Jiaying Abby Guo, Robert Strzepek, Anusuya Willis, Aaron Ferderer, and Lennart Thomas Bach
Biogeosciences, 19, 3683–3697, https://doi.org/10.5194/bg-19-3683-2022, https://doi.org/10.5194/bg-19-3683-2022, 2022
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Ocean alkalinity enhancement is a CO2 removal method with significant potential, but it can lead to a perturbation of the ocean with trace metals such as nickel. This study tested the effect of increasing nickel concentrations on phytoplankton growth and photosynthesis. We found that the response to nickel varied across the 11 phytoplankton species tested here, but the majority were rather insensitive. We note, however, that responses may be different under other experimental conditions.
Charly A. Moras, Lennart T. Bach, Tyler Cyronak, Renaud Joannes-Boyau, and Kai G. Schulz
Biogeosciences, 19, 3537–3557, https://doi.org/10.5194/bg-19-3537-2022, https://doi.org/10.5194/bg-19-3537-2022, 2022
Short summary
Short summary
This research presents the first laboratory results of quick and hydrated lime dissolution in natural seawater. These two minerals are of great interest for ocean alkalinity enhancement, a strategy aiming to decrease atmospheric CO2 concentrations. Following the dissolution of these minerals, we identified several hurdles and presented ways to avoid them or completely negate them. Finally, we proceeded to various simulations in today’s oceans to implement the strategy at its highest potential.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Michelle N. Simone, Kai G. Schulz, Joanne M. Oakes, and Bradley D. Eyre
Biogeosciences, 18, 1823–1838, https://doi.org/10.5194/bg-18-1823-2021, https://doi.org/10.5194/bg-18-1823-2021, 2021
Short summary
Short summary
Estuaries are responsible for a large contribution of dissolved organic carbon (DOC) to the global C cycle, but it is unknown how this will change in the future. DOC fluxes from unvegetated sediments were investigated ex situ subject to conditions of warming and ocean acidification. The future climate shifted sediment fluxes from a slight DOC source to a significant sink, with global coastal DOC export decreasing by 80 %. This has global implications for C cycling and long-term C storage.
Andrea J. Fassbender, James C. Orr, and Andrew G. Dickson
Biogeosciences, 18, 1407–1415, https://doi.org/10.5194/bg-18-1407-2021, https://doi.org/10.5194/bg-18-1407-2021, 2021
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A decline in upper-ocean pH with time is typically ascribed to ocean acidification. A more quantitative interpretation is often confused by failing to recognize the implications of pH being a logarithmic transform of hydrogen ion concentration rather than an absolute measure. This can lead to an unwitting misinterpretation of pH data. We provide three real-world examples illustrating this and recommend the reporting of both hydrogen ion concentration and pH in studies of ocean chemical change.
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
Short summary
Short summary
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.
Cited articles
Anbeek, C.: The dependence of dissolution rates on grain size for some fresh and weathered feldspars, Geochim. Cosmochim. Ac., 56, 3957–3970, 1992.
Bach, L. T.: The additionality problem of Ocean Alkalinity Enhancement, Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2023-122, in review, 2023.
Bach, L. T., Gill, S. J., Rickaby, R. E. M., Gore, S., and Renforth, P.: CO2 removal with enhanced weathering and ocean alkalinity enhancement: Potential risks and co-benefits for marine pelagic ecosystems, Front. Clim., 1, 7, https://doi.org/10.3389/fclim.2019.00007, 2019.
Ben-Yaakov, S. and Goldhaber, M. B.: The influence of seawater composition on the apparent constants of the carbonate system, Deep-Sea Res., 20, 87–99, 1972.
Bockmon, E. E. and Dickson, A. G.: An inter-laboratory comparison assessing the quality of seawater carbon dioxide measurements, Mar. Chem., 171, 36–43, 2015.
Byrne, R. H. Robert-Baldo, B., Thompson, S. W., and Chen, C. T. A.: Seawater pH measurements: an at-sea comparison of spectrophotometric and potentiometric methods, Deep-Sea Res., 35, 1405–1410, 1988.
Chave, K. E. and Suess, E.: Calcium Carbonate Saturation in Seawater: Effects of Dissolved Organic Matter, Limnol. Oceanogr., 15, 633–637, 1970.
Deffeys, K. S.: Carbonate equilibria: a graphic and algebraic approach, Limnol. Oceanogr., 10, 412–426, 1965.
Dickson. A. G.: The carbon dioxide system in seawater: equilibrium chemistry and measurements, in: Guide to Best Practices in Ocean Acidification Research and Data Reporting, edited by: Riebesell, U., Fabry, V. J., Hansson, L., Gattuso, J. P., 260 pp., Luxembourg, ISBN 1813-8519, 2010.
Dickson, A. G., Wesolowski, D. J., Palmer, D. A., and Mesmer, R. E.: Dissociation constant of bisulfate ion in aqueous sodium chloride solutions to 250 ∘C, J. Phys. Chem., 94, 7978–7985, https://doi.org/10.1021/j100383a042, 1990.
Dickson, A. G., Sabine, C. L., and Christian, J. R.: Guide to best practices for ocean CO2 measurements, PICES Special Publication 3, IOCCP Report 8, North Pacific Marine Science Organization, Sidney, British Columbia, 191 pp., https://doi.org/10.25607/OBP-1342, 2007.
Douglas, N. K. and Byrne, R. H.: Achieving accurate spectrophotometric pH measurements using unpurified meta-cresol purple, Mar. Chem., 190, 66–72, https://doi.org/10.1016/j.marchem.2017.02.004, 2017.
Eisaman, M. D., Geilert, S., Renforth, P., Bastianini, L., Campbell, J., Dale, A. W., Foteinis, S., Grasse, P., Hawrot, O., Löscher, C. R., Rau, G. H., and Rønning, J.: Assessing the technical aspects of ocean-alkalinity-enhancement approaches, in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P., Copernicus Publications, State Planet, 2-oae2023, 3, https://doi.org/10.5194/sp-2-oae2023-3-2023, 2023.
Fennel, K., Long, M. C., Algar, C., Carter, B., Keller, D., Laurent, A., Mattern, J. P., Musgrave, R., Oschlies, A., Ostiguy, J., Palter, J. B., and Whitt, D. B.: Modelling considerations for research on ocean alkalinity enhancement (OAE), in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P., Copernicus Publications, State Planet, 2-oae2023, 9, https://doi.org/10.5194/sp-2-oae2023-9-2023, 2023.
Flipkens, G., Fuhr, M., Fiers, G., Meysman, F. J. R., Town, R. M., and Blust, R.: Enhanced olivine dissolution in seawater through continuous grain collisions, Geochim. Cosmochim. Ac., 359, 84–99, https://doi.org/10.1016/j.gca.2023.09.002, 2023.
Fong, M. B. and Dickson, A. G.: Insights from GO-SHIP hydrography data into the thermodynamic consistency of CO2 system measurements in seawater, Mar. Chem., 211, 52–63, 2019.
Fuhr, K., Geilert, S., Schmidt, M., Liebetrau, V., Vogt, C., Ledwig, B., and Wallmann, K.: Kinetics of olivine weathering in seawater: An experimental study, Front. Clim., 4, 831587, https://doi.org/10.3389/fclim.2022.831587, 2022.
He, J. and Tyka, M. D.: Limits and CO2 equilibration of near-coast alkalinity enhancement, Biogeosciences, 20, 27–43, https://doi.org/10.5194/bg-20-27-2023, 2023.
Ho, D. T., Bopp, L., Palter, J. B., Long, M. C., Boyd, P. W., Neukermans, G., and Bach, L. T.: Monitoring, reporting, and verification for ocean alkalinity enhancement, in: Guide to Best Practices in Ocean Alkalinity Enhancement Research, edited by: Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P., Copernicus Publications, State Planet, 2-oae2023, 12, https://doi.org/10.5194/sp-2-oae2023-12-2023, 2023.
Hudson-Heck, E., Liu, X., and Byrne, R. H.: Purification and Physical–Chemical Characterization of Bromocresol Purple for Carbon System Measurements in Freshwaters, Estuaries, and Oceans, ACS Omega, 6, 17941–17951, 2021.
Humphreys, M. P., Daniels, C. J., Wolf-Gladrow, D. A., Tyrell, T., and Achterberg, E. P.: On the influence of marine biogeochemical processes over CO2 exchange between the atmosphere and ocean, Mar. Chem., 199, 1–11, https://doi.org/10.1016/j.marchem.2017.12.006, 2018.
Jiang, L.-Q., Feely, R. A., Carter, B. R., Greeley, D. J., Gledhill, D. K., and Arzayus, K. M.: Climatological distribution of aragonite saturation state in the Global Oceans, Global Biogeochem. Cy., 29, 1656–1673, https://doi.org/10.1002/2015gb005198, 2015.
Lauvset, S. K., Key, R. M., Olsen, A., van Heuven, S., Velo, A., Lin, X., Schirnick, C., Kozyr, A., Tanhua, T., Hoppema, M., Jutterström, S., Steinfeldt, R., Jeansson, E., Ishii, M., Perez, F. F., Suzuki, T., and Watelet, S.: A new global interior ocean mapped climatology: the 1∘ × 1∘ GLODAP version 2, Earth Syst. Sci. Data, 8, 325–340, https://doi.org/10.5194/essd-8-325-2016, 2016.
Lenc, R., Schulz, K. G., and Bach, L. T.: Assessing the risk for alkalinity loss due to carbonate precipitation on particles after an ocean Alkalinity Enhancement Operation, Masters Thesis, Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, https://figshare.utas.edu.au/category (last access: 9 November 2023), 2023.
Marion, G. M., Millero, F. J., and Feistel, R.: Precipitation of solid phase calcium carbonates and their effect on application of seawater SA–T–P models, Ocean Sci., 5, 285–291, https://doi.org/10.5194/os-5-285-2009, 2009.
Montserrat, F., Renforth, P., Hartmann, J., Leermakers, M., Knops, P., and Meysman, F. J. R.: Olivine Dissolution in Seawater: Implications for CO2 Sequestration through Enhanced Weathering in Coastal Environments, Environ. Sci. Technol., 51, 3960–3972, https://doi.org/10.1021/acs.est.6b05942, 2017.
Moras, C. A., Bach, L. T., Cyronak, T., Joannes-Boyau, R., and Schulz, K. G.: Ocean alkalinity enhancement – avoiding runaway CaCO3 precipitation during quick and hydrated lime dissolution, Biogeosciences, 19, 3537–3557, https://doi.org/10.5194/bg-19-3537-2022, 2022.
Moras, C., Bach, L., Cyronak, T., Joannes-Boyau, R., and Schulz, K.: Effects of grain size and seawater salinity on brucite dissolution and secondary calcium carbonate precipitation kinetics: implications for Ocean Alkalinity Enhancement, EGU General Assembly 2023, Vienna, Austria, 24–28 April 2023, EGU23-330, https://doi.org/10.5194/egusphere-egu23-330, 2023a.
Moras, C. A., Bach, L. T., Cyronak, T., Joannes-Boyau, R., and Schulz, K. G.: Preparation and quality control of in-house reference materials for marine dissolved inorganic carbon and total alkalinity measurements, Limnol. Oceanogr. Methods, https://doi.org/10.1002/lom3.10570, online first, 2023b.
Morse, J., Arvidson, R. S., and Lüttge, A.: Calcium Carbonate Formation and Dissolution, Chem. Rev., 107, 342–381, 2007.
Mucci, A.: The solubility of calcite and aragonite in seawater at various salinities, temperatures, and one atmosphere total pressure, Am. J. Sci., 283, 781–799, 1983.
Newton, J. A., Feely, R. A., Jewett, E. B., Williamson, P., and Mathis, J.: Global Ocean Acidification Observing Network: Requirements and Governance Plan, 2nd edn., UNESCO IOC, 2015.
Orr, J. C., Epitalon, J.-M., and Gattuso, J.-P.: Comparison of ten packages that compute ocean carbonate chemistry, Biogeosciences, 12, 1483–1510, https://doi.org/10.5194/bg-12-1483-2015, 2015.
Orr, J. C., Epitalon, J. M., Dickson, A. G., and Gattuso, J. P.: Routine uncertainty propagation for the marine carbon dioxide system, Mar. Chem., 207, 84–107, 2018.
Pan, Y., Li, Y., Ma, Q., He, H., Wang, S., Cai, W.-J., Dong, B. Di, Y., Fu, W., and Chen, C.-T. A.: The role of Mg2+ in inhibiting CaCO3 precipitation from seawater, Mar. Chem., 237, 104036, https://doi.org/10.1016/j.marchem.2021.104036, 2021.
Rau, G. H., Carroll, S. A., Bourcier, W. L., Singleton, M. J., Smith, M. M., and Aines, R. D.: Direct electrolytic dissolution of silicate minerals for air CO2 mitigation and carbon-negative H2 production, P. Natl. Acad. Sci. USA, 110, 10095–10100, https://doi.org/10.1073/pnas.1222358110, 2013.
Schulz, K. G. and Maher, D. T.: Atmospheric Carbon Dioxide and Changing Ocean Chemistry, in: Marine Pollution – Monitoring, Management and Mitigation, edited by: Reichelt-Brushett, A., Springer, https://doi.org/10.1007/978-3-031-10127-4, 2023.
Schulz, K. G., Bach, L. T., Bellerby, R. G. J., Bermúdez, R., Büdenbender, J., Boxhammer, T., Czerny, J., Engel, A., Ludwig, A., Meyerhöfer, M., Larsen, A., Paul, A. J., Sswat, M., and Riebesell, U.: Phytoplankton blooms at increasing levels of atmospheric carbon dioxide: Experimental evidence for negative effects on prymnesiophytes and positive on small picoeukaryotes, Frontiers, Mar. Sci., 4, 64, https://doi.org/10.3389/fmars.2017.00064, 2017.
Simkiss, K.: The inhibitory effects of some metabolites on the precipitation of calcium carbonate from artificial and natural seawater, ICES J. Mar. Sci., 29, 6–18, 1964.
Subhas, A. V., Marx, L., Reynolds, S., Flohr, A., Mawji, E. W., Brown, P. J., and Cael, B. B.: Microbial ecosystem responses to alkalinity enhancement in the North Atlantic Subtropical Gyre, Front. Clim., 4, 784997, https://doi.org/10.3389/fclim.2022.784997, 2022.
Sulpis, O., Lauvset, S. K., and Hagens, M.: Current estimates of K1* K2* appear inconsistent with measured CO2 system parameters in cold oceanic regions, Ocean Sci., 16, 847–862, https://doi.org/10.5194/os-16-847-2020, 2020.
Takeshita, Y., Warren, J. K., Liu, X., Spaulding, R. S., Byrne, R. H., Carter, B. R., DeGrandpre, M. D., Murata, A., and Watanabe, S.: Consistency and stability of purified meta-cresol purple for spectrophotometric pH measurements in seawater, Mar. Chem., 236, 104018, https://doi.org/10.1016/j.marchem.2021.104018, 2021.
Turner, D. R., Achterberg, E. P., Chen, C.-T. A., Clegg, S. L., Hatje, V., Maldonado, M. T., Snader, S. G., van den Berg, C. M. G., and Wells, M.: Toward a Quality-Controlled and Accessible Pitzer Model for Seawater and Related Systems, Front. Mar. Sci., 3, 139, https://doi.org/10.3389/fmars.2016.00139, 2016.
Tyka, M. D., Van Arsdale, C., and Platt, J. C.: CO2 capture by pumping surface acidity to the depp ocean, Energy Environ. Sci., 15, 786–798, https://doi.org/10.1039/D1EE01532J, 2022.
Tyrell, T. and Zeebe, R. E.: History of carbonate ion concentration over the last 100 million years, Geochim. Cosmochim. Ac., 68, 3521–3530, 2004.
Uppström, L. R.: The boron/chlorinity ratio of deep-sea water from the Pacific Ocean, Deep-Sea Res. Oceanogr. Abstracts, 21, 161–162, https://doi.org/10.1016/0011-7471(74)90074-6, 1974.
van Heuven, S., Pierrot, D., Rae, J. W. B., Lewis, E., and Wallace, D. W. R.: MATLAB Program Developed for CO2 System Calculations, ORNL/CDIAC-105b, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tennessee, https://github.com/jamesorr/CO2SYS-MATLAB (last access: 6 November 2023), 2011.
Zeebe, R. and Wolf-Gladrow, D.: CO2 in Seawater: Equilibrium, Kinetics, Isotopes, Elsevier Science B.V., Amsterdam, the Netherlands, 360 pp., ISBN 0444509461, 2001.
Zhong, S. and Mucci, A.: Calcite and aragonite precipitation from seawater solutions of various salinities: Precipitation rates and overgrowth compositions., in: Kinetic Geochemistry, edited by: Schott, J. and Lasaga, A. C., Chem. Geol., 78, 283–299, 1989.
Short summary
Ocean alkalinity enhancement is a promising approach for long-term anthropogenic carbon dioxide sequestration, required to avoid catastrophic climate change. In this chapter we describe its impacts on seawater carbonate chemistry speciation and highlight pitfalls that need to be avoided during sampling, storage, measurements, and calculations.
Ocean alkalinity enhancement is a promising approach for long-term anthropogenic carbon dioxide...
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