Articles | Volume 21, issue 1
https://doi.org/10.5194/bg-21-261-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-21-261-2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The additionality problem of ocean alkalinity enhancement
Lennart Thomas Bach
CORRESPONDING AUTHOR
Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, TAS, Australia
Related authors
Patricia Grasse, Kristin Doering, Allanah J. Paul, Avy Bernales, Sonia Sanchez Ramirez, Elisabeth von der Esch, Michelle Graco, Tim Boxhammer, Lennart T. Bach, Ulf Riebesell, and Martin Frank
EGUsphere, https://doi.org/10.5194/egusphere-2025-5079, https://doi.org/10.5194/egusphere-2025-5079, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
This study shows how changing ocean conditions off Peru influence plankton communities and the marine silicon cycle. During a coastal El Niño, we carried out a large field experiment that, for the first time, determined the silicon isotope fractionation factor for silicoflagellates, providing a novel tool for understanding dSi utilization in the past.
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
Short summary
Short summary
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
Short summary
Short summary
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.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Kai G. Schulz, Lennart T. Bach, and Andrew G. Dickson
State Planet, 2-oae2023, 2, https://doi.org/10.5194/sp-2-oae2023-2-2023, https://doi.org/10.5194/sp-2-oae2023-2-2023, 2023
Short summary
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.
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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.
Patricia Grasse, Kristin Doering, Allanah J. Paul, Avy Bernales, Sonia Sanchez Ramirez, Elisabeth von der Esch, Michelle Graco, Tim Boxhammer, Lennart T. Bach, Ulf Riebesell, and Martin Frank
EGUsphere, https://doi.org/10.5194/egusphere-2025-5079, https://doi.org/10.5194/egusphere-2025-5079, 2025
This preprint is open for discussion and under review for Biogeosciences (BG).
Short summary
Short summary
This study shows how changing ocean conditions off Peru influence plankton communities and the marine silicon cycle. During a coastal El Niño, we carried out a large field experiment that, for the first time, determined the silicon isotope fractionation factor for silicoflagellates, providing a novel tool for understanding dSi utilization in the past.
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
Short summary
Short summary
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
Short summary
Short summary
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.
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
Short summary
Short summary
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
Short summary
Short summary
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.
Kai G. Schulz, Lennart T. Bach, and Andrew G. Dickson
State Planet, 2-oae2023, 2, https://doi.org/10.5194/sp-2-oae2023-2-2023, https://doi.org/10.5194/sp-2-oae2023-2-2023, 2023
Short summary
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.
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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
Short summary
Short summary
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.
Cited articles
Adkins, J. F., Naviaux, J. D., Subhas, A. V, Dong, S., and Berelson, W. M.: The Dissolution Rate of CaCO_3 in the Ocean, Annu. Rev. Mar. Sci., 13, 57–80, https://doi.org/10.1146/annurev-marine-041720, 2020.
Albright, R., Caldeira, L., Hosfelt, J., Kwiatkowski, L., Maclaren, J. K., Mason, B. M., Nebuchina, Y., Ninokawa, A., Pongratz, J., Ricke, K. L., Rivlin, T., Schneider, K., Sesboüé, M., Shamberger, K., Silverman, J., Wolfe, K., Zhu, K., and Caldeira, K.: Reversal of ocean acidification enhances net coral reef calcification, Nature, 531, 362–365, https://doi.org/10.1038/nature17155, 2016.
Aller, R. C.: Carbonate Dissolution in Nearshore Terrigenous Muds: The Role of Physical and Biological Reworking, J. Geol., 90, 79–95, https://doi.org/10.1086/628652, 1982.
Archer, D., Kheshgi, H., and Maier-Reimer, E.: Dynamics of fossil fuel CO2 neutralization by marine CaCO_3, Global Biogeochem. Cy., 12, 259–276, https://doi.org/10.1029/98GB00744, 1998.
Bach, L. T.: The additionality problem of Ocean Alkalinity Enhancement: Underlying experimental and observational data, Zenodo [data set], https://doi.org/10.5281/zenodo.8191516, 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, 1–21, https://doi.org/10.3389/fclim.2019.00007, 2019.
Caserini, S., Storni, N., and Grosso, M.: The Availability of Limestone and Other Raw Materials for Ocean Alkalinity Enhancement, Global Biogeochem. Cy., 36, e2021GB007246, https://doi.org/10.1029/2021GB007246, 2022.
Dickson, A. G., Afghan, J. D., and Anderson, G. C.: Reference materials for oceanic CO2 analysis: a method for the certification of total alkalinity, Mar. Chem., 80, 185–197, https://doi.org/10.1016/S0304-4203(02)00133-0, 2003.
Dickson, A. G., Sabine, C. L., and Christian, J. R.: Guide to Best Practices for Ocean CO2 Measurements, PICES Spec., PICES, Sidney, ISBN 1-897176-07-4, 2007.
Eisaman, M. D., Rivest, J. L. B., Karnitz, S. D., Lannoy, C. De, Jose, A., Devaul, R. W., and Hannun, K.: International Journal of Greenhouse Gas Control Indirect ocean capture of atmospheric CO2: Part II, Understanding the cost of negative emissions, Int. J. Greenh. Gas Con., 70, 254–261, https://doi.org/10.1016/j.ijggc.2018.02.020, 2018.
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.
Fakhraee, M., Planavsky, N. J., and Reinhard, C. T.: Ocean alkalinity enhancement through restoration of blue carbon ecosystems, Nat. Sustain., 6, 1087–1094, https://doi.org/10.1038/s41893-023-01128-2, 2023.
Feng, E. Y., Koeve, W., Keller, D. P., and Oschlies, A.: Model-Based Assessment of the CO2 Sequestration Potential of Coastal Ocean Alkalinization, Earths Future, 5, 1252–1266, https://doi.org/10.1002/eft2.273, 2017.
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.
Flipkens, G., Fuhr, M., 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.
Fuhr, M., 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, 1–20, https://doi.org/10.3389/fclim.2022.831587, 2022.
Gattuso, J.-P., Epitalon, J.-M., Lavigne, H., and Orr, J.: Seacarb: seawater carbonate chemistry with R. R package version 3.0, https://cran.r-project.org/web/packages/seacarb/index.html (last access: 17 October 2023), 2021.
Hangx, S. J. T. and Spiers, C. J.: Coastal spreading of olivine to control atmospheric CO2 concentrations: A critical analysis of viability, Int. J. Greenh. Gas Con., 3, 757–767, https://doi.org/10.1016/j.ijggc.2009.07.001, 2009.
Hansen, H. P. and Koroleff, F.: Determination of nutrients, in: Methods of Seawater Analysis, edited by: Grasshoff, K., Kremling, K., and Ehrhardt, M., Wiley-VCH, Weinheim, 159–226, https://doi.org/10.1002/9783527613984 1999.
Hartmann, J., West, A. J., Renforth, P., Köhler, P., de la Rocha, C., Wolf-Gladrow, D., Dürr, H. H., and Scheffran, J.: Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification, Rev. Geophys., 51, 113–149, https://doi.org/10.1002/rog.20004.1.Institute, 2013.
Hartmann, J., Suitner, N., Lim, C., Schneider, J., Marín-Samper, L., Arístegui, J., Renforth, P., Taucher, J., and Riebesell, U.: Stability of alkalinity in ocean alkalinity enhancement (OAE) approaches – consequences for durability of CO2 storage, Biogeosciences, 20, 781–802, https://doi.org/10.5194/bg-20-781-2023, 2023.
Harvey, L. D. D.: Mitigating the atmospheric CO2 increase and ocean acidification by adding limestone powder to upwelling regions, J. Geophys. Res.-Oceans, 113, 1–21, https://doi.org/10.1029/2007JC004373, 2008.
Havukainen, M., Waldén, P., and Kahiluoto, H.: Clean Development Mechanism, in: Encyclopedia of Sustainable Management, edited by: Idowu, S. O., Springer Nature Switzerland, 1–5, https://doi.org/10.1016/B978-0-12-375067-9.00127-3, 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.
Humphreys, M. P., Gregor, L., Pierrot, D., van Heuven, S. M. A. C., Lewis, E. R., and Wallace, D. W. R.: PyCO2SYS: marine carbonate system calculations in Python, Zenodo, https://doi.org/10.5281/zenodo.3744275, 2020.
Keller, D. P., Lenton, A., Littleton, E. W., Oschlies, A., Scott, V., and Vaughan, N. E.: The Effects of Carbon Dioxide Removal on the Carbon Cycle, Curr. Clim. Change Rep., 4, 250–265, https://doi.org/10.1007/s40641-018-0104-3, 2018.
Krumins, V., Gehlen, M., Arndt, S., Van Cappellen, P., and Regnier, P.: Dissolved inorganic carbon and alkalinity fluxes from coastal marine sediments: model estimates for different shelf environments and sensitivity to global change, Biogeosciences, 10, 371–398, https://doi.org/10.5194/bg-10-371-2013, 2013.
de Lannoy, C. F., Eisaman, M. D., Jose, A., Karnitz, S. D., DeVaul, R. W., Hannun, K., and Rivest, J. L. B.: Indirect ocean capture of atmospheric CO2: Part I, Prototype of a negative emissions technology, Int. J. Greenh. Gas Con., 70, 243–253, https://doi.org/10.1016/j.ijggc.2017.10.007, 2018.
Lewis, E. L. and Perkin, R. G.: Salinity: Its definition and calculation, J. Geophys. Res.-Oceans, 83, 466–478, https://doi.org/10.1029/jc083ic01p00466, 1978.
Lezaun, J.: Hugging the Shore: Tackling Marine Carbon Dioxide Removal as a Local Governance Problem, Front. Clim., 3, 1–6, https://doi.org/10.3389/fclim.2021.684063, 2021.
Liu, Y., Jiao, J. J., Liang, W., Santos, I. R., Kuang, X., and Robinson, C. E.: Inorganic carbon and alkalinity biogeochemistry and fluxes in an intertidal beach aquifer: Implications for ocean acidification, J. Hydrol., 595, 126036, https://doi.org/10.1016/j.jhydrol.2021.126036, 2021.
Lueker, T. J., Dickson, A. G., and Keeling, C. D.: Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: Validation based on laboratory measurements of CO2 in gas and seawater at equilibrium, Mar. Chem., 70, 105–119, https://doi.org/10.1016/S0304-4203(00)00022-0, 2000.
Lunstrum, A. and Berelson, W.: CaCO_3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time, Geochim. Cosmochim. Ac., 329, 168–184, https://doi.org/10.1016/j.gca.2022.04.031, 2022.
Meysman, F. J. R. and Montserrat, F.: Negative CO2 emissions via enhanced silicate weathering in coastal environments, Biol. Lett., 13, 20160905, https://doi.org/10.1098/rsbl.2016.0905, 2017.
Michaelowa, A., Hermwille, L., Obergassel, W., and Butzengeiger, S.: Additionality revisited: guarding the integrity of market mechanisms under the Paris Agreement, Clim. Pol., 19, 1211–1224, https://doi.org/10.1080/14693062.2019.1628695, 2019.
Middelburg, J. J., Soetaert, K., and Hagens, M.: Ocean Alkalinity, Buffering and Biogeochemical Processes, Rev. Geophys., 58, e2019RG000681, https://doi.org/10.1029/2019RG000681, 2020.
Milliman, J. D., Troy, P. J., Balch, W. M., Adams, A. K., Li, Y.-H., and Mackenzie, F. T.: Biologically mediated dissolution of calcium carbonate above the chemical lysocline?, Deep Sea Res. Pt. I, 46, 1653–1669, https://doi.org/10.1016/S0967-0637(99)00034-5, 1999.
Mongin, M., Baird, M. E., Lenton, A., Neill, C., and Akl, J.: Reversing ocean acidification along the Great Barrier Reef using alkalinity injection, Environ. Res. Lett., 16, 064068, https://doi.org/10.1088/1748-9326/ac002d, 2021.
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.
Morse, J. W., Zullig, J. J., Bernstein, L. D., Millero, F. J., Milne, P., Mucci, A., and Choppin, G. R.: Chemistry of calcium carbonate-rich shallow water sediments in the Bahamas, Am. J. Sci., 285, 147–185, https://doi.org/10.2475/ajs.285.2.147, 1985.
Morse, J. W., Gledhill, D. K., and Millero, F. J.: CaCO_3 precipitation kinetics in waters from the great Bahama bank: Implications for the relationship between bank hydrochemistry and whitings, Geochim. Cosmochim. Ac., 67, 2819–2826, https://doi.org/10.1016/S0016-7037(03)00103-0, 2003.
Mucci, A.: The solubility of calcite and aragonite in seawater at various salinities, temperatures, and one atmosphere total pressure, Am. J. Sci., 283, 780–799, 1983.
Nemet, G. F., Callaghan, M. W., Creutzig, F., Fuss, S., Hartmann, J., Hilaire, J., Lamb, W. F., Minx, J. C., Rogers, S., and Smith, P.: Negative emissions – Part 3: Innovation and upscaling, Environ. Res. Lett., 13, 06300, https://doi.org/10.1088/1748-9326/aabff4, 2018.
Oelkers, E. H., Declercq, J., Saldi, G. D., Gislason, S. R., and Schott, J.: Olivine dissolution rates: A critical review, Chem. Geol., 500, 1–19, https://doi.org/10.1016/j.chemgeo.2018.10.008, 2018.
Perkins, A. K., Santos, I. R., Rose, A. L., Schulz, K. G., Grossart, H. P., Eyre, B. D., Kelaher, B. P., and Oakes, J. M.: Production of dissolved carbon and alkalinity during macroalgal wrack degradation on beaches: a mesocosm experiment with implications for blue carbon, Biogeochemistry, 160, 159–175, https://doi.org/10.1007/s10533-022-00946-4, 2022.
Rau, G. H. and Caldeira, K.: Enhanced carbonate dissolution: A means of sequestering waste CO2 as ocean bicarbonate, Energ. Conver. Manag., 40, 1803–1813, https://doi.org/10.1016/S0196-8904(99)00071-0, 1999.
Reckhardt, A., Beck, M., Seidel, M., Riedel, T., Wehrmann, A., Bartholomä, A., Schnetger, B., Dittmar, T., and Brumsack, H. J.: Carbon, nutrient and trace metal cycling in sandy sediments: Acomparison of high-energy beaches and backbarrier tidal flats, Estuar. Coast. Shelf S., 159, 1–14, https://doi.org/10.1016/j.ecss.2015.03.025, 2015.
Renforth, P.: The negative emission potential of alkaline materials, Nat. Commun., 10, 1401, https://doi.org/10.1038/s41467-019-09475-5, 2019.
Renforth, P. and Henderson, G.: Assessing ocean alkalinity for carbon sequestration, Rev. Geophys., 55, 636–674, https://doi.org/10.1002/2016RG000533, 2017.
Renforth, P., Baltruschat, S., Peterson, K., Mihailova, B. D., and Hartmann, J.: Using ikaite and other hydrated carbonate minerals to increase ocean alkalinity for carbon dioxide removal and environmental remediation, Joule, 6, 2674–2679, https://doi.org/10.1016/j.joule.2022.11.001, 2022.
Saderne, V., Fusi, M., Thomson, T., Dunne, A., Mahmud, F., Roth, F., Carvalho, S., and Duarte, C. M.: Total alkalinity production in a mangrove ecosystem reveals an overlooked Blue Carbon component, Limnol. Oceanogr. Lett., 6, 61–67, https://doi.org/10.1002/lol2.10170, 2021.
Schuiling, R. D. and de Boer, P. L.: Coastal spreading of olivine to control atmospheric CO2 concentrations: A critical analysis of viability, Comment: Nature and laboratory models are different, Int. J. Greenh. Gas Con., 4, 855–856, https://doi.org/10.1016/j.ijggc.2010.04.012, 2010.
Schuiling, R. D. and Krijgsman, P.: Enhanced weathering: An effective and cheap tool to sequester CO2, Clim. Change, 74, 349–354, https://doi.org/10.1007/s10584-005-3485-y, 2006.
Schulz, K. G., Bach, L. T., and Dickson, A. G.: Seawater carbonate chemistry considerations for ocean alkalinity enhancement research: theory, measurements, and calculations, 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, 2, https://doi.org/10.5194/sp-2-oae2023-2-2023, 2023.
Subhas, A. V., Dong, S., Naviaux, J. D., Rollins, N. E., Ziveri, P., Gray, W., Rae, J. W. B., Liu, X., Byrne, R. H., Chen, S., Moore, C., Martell-Bonet, L., Steiner, Z., Antler, G., Hu, H., Lunstrum, A., Hou, Y., Kemnitz, N., Stutsman, J., Pallacks, S., Dugenne, M., Quay, P. D., Berelson, W. M., and Adkins, J. F.: Shallow Calcium Carbonate Cycling in the North Pacific Ocean, Global Biogeochem. Cy., 36, 1–22, https://doi.org/10.1029/2022GB007388, 2022.
Sulpis, O., Jeansson, E., Dinauer, A., Lauvset, S. K., and Middelburg, J. J.: Calcium carbonate dissolution patterns in the ocean, Nat. Geosci., 14, 423–428, https://doi.org/10.1038/s41561-021-00743-y, 2021.
Sulpis, O., Agrawal, P., Wolthers, M., Munhoven, G., Walker, M., and Middelburg, J. J.: Aragonite dissolution protects calcite at the seafloor, Nat. Commun., 13, 1–8, https://doi.org/10.1038/s41467-022-28711-z, 2022.
Torres, M. E., Hong, W. L., Solomon, E. A., Milliken, K., Kim, J. H., Sample, J. C., Teichert, B. M. A., and Wallmann, K.: Silicate weathering in anoxic marine sediment as a requirement for authigenic carbonate burial, Earth. Sci. Rev., 200, 102960, https://doi.org/10.1016/j.earscirev.2019.102960, 2020.
Tyka, M. D., Van Arsdale, C., and Platt, J. C.: CO2 capture by pumping surface acidity to the deep ocean, Energ. Environ. Sci., 15, 786–798, https://doi.org/10.1039/d1ee01532j, 2022.
Wallmann, K., Diesing, M., Scholz, F., Rehder, G., Dale, A. W., Fuhr, M., and Suess, E.: Erosion of carbonate-bearing sedimentary rocks may close the alkalinity budget of the Baltic Sea and support atmospheric CO2 uptake in coastal seas, Front. Mar. Sci., 9, 1–15, https://doi.org/10.3389/fmars.2022.968069, 2022.
Zhong, S. and Mucci, A.: Calcite and aragonite precipitation from seawater solutions of various salinities: Precipitation rates and overgrowth compositions, Chem. Geol., 78, 283–299, https://doi.org/10.1016/0009-2541(89)90064-8, 1989.
Co-editor-in-chief
Reaching the Paris Agreement targets to limit global warming to 1.5 or 2°C implies not only reducing emissions, but also active carbon dioxide removal from the atmosphere. While land-based carbon dioxide removal or negative emission technologies have received most attention, ocean solutions are increasingly being considered. Ocean alkalinity enhancement (OAE), or alkalinization, is one promising ocean-based carbon dioxide technology. However, any new carbon dioxide removal technique needs thorough investigations for its effectiveness, longevity, benefits and lack of disbenefits, financial viability, social acceptance and governability. The paper by Bach is a nice illustration of the type of research that must be done if we are to consider large scale application of OAE. It focuses on the additionality problem of ocean alkalinity enhancement, specifically it investigates how the addition of alkalinity modifies the natural alkalinity cycle and in that way the efficiency of carbon dioxide sequestration.
Reaching the Paris Agreement targets to limit global warming to 1.5 or 2°C implies not only...
Short summary
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.
Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method....
Altmetrics
Final-revised paper
Preprint