Schlagwort: ocean alkalinity enhancement

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Gao et al. (2026): Assessing the effects of ocean alkalinity enhancement on marine protozoa: physiological dynamics and transcriptomic responses

Zuyuan Gao, Mengwen Pang, Mingjie Li, Yuzhen Ming, Hongbin Liu and Kedong Yin, IN: Applied and Environmental Microbiology, https://doi.org/10.1128/aem.00298-26

Ocean alkalinity enhancement (OAE) is proposed as a potential tool to remove atmospheric CO₂ and mitigate climate change. However, the effects of OAE on marine protozoa remain poorly understood. In this study, the authors conducted acute and acclimated experiments on two heterotrophic nanoflagellates, i.e., Cafeteria burkhardae and Paraphysomonas longispina, to investigate their responses to two substances (NaHCO₃ and NaOH) at low (set ~2,600 µmol L⁻¹) and high (set ~4,000 µmol L⁻¹) levels, respectively.

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Peer-reviewed Publications

Gao et al. (2026): Assessing the effects of ocean alkalinity enhancement on marine protozoa: physiological dynamics and transcriptomic responses

Zuyuan Gao, Mengwen Pang, Mingjie Li, Yuzhen Ming, Hongbin Liu, and Kedong Yin, IN: Applied and Environmental Microbiology, https://doi.org/10.1128/AEM.00298-26

Ocean alkalinity enhancement (OAE) is proposed as a potential tool to remove atmospheric CO₂ and mitigate climate change. However, the effects of OAE on marine protozoa remain poorly understood. In this study, the authors conducted acute and acclimated experiments on two heterotrophic nanoflagellates, i.e., Cafeteria burkhardae and Paraphysomonas longispina, to investigate their responses to two substances (NaHCO₃ and NaOH) at low (set ~2,600 µmol L⁻¹) and high (set ~4,000 µmol L⁻¹) levels, respectively.

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Peer-reviewed Publications

Saez Moreno et al. (2026): The role of temperature and salinity on ocean alkalinity enhancement performance

Matias Saez Moreno, Jens Hartmann, Janine Börker, Peggy Bartsch, and Charly Andre Moras, IN: EGUsphere, https://doi.org/10.5194/egusphere-2026-3277

Ocean alkalinity enhancement (OAE) is a promising carbon dioxide removal approach but its effectiveness is constrained by uncertainties in dissolution kinetics and carbonate precipitation under varying ocean conditions. Here, the authors systematically quantified the dissolution and net alkalinity delivery of three common OAE feedstocks, i.e., NaHCO₃, Ca(OH)₂, Mg(OH)₂, across 16 temperature–salinity combinations (T = 4, 12, 20, 28 °C and S = 24, 29, 34, 38). Each treatment targeted an alkalinity increase of 500 µmol kg⁻¹ and was monitored over 11 days to track changes in total alkalinity (TA) and dissolved inorganic carbon (DIC).

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Peer-reviewed Publications

Liu et al. (2026): A new pathway to enhance the oceanic carbon sink: inorganic carbonate precipitation driven by calcium–alkali coupling

Shan Shan Liu, Jin Ming Song, Xue Gang Li, Hua Mao Yuan, Li Qin Duan et al., IN: Journal of Environmental Management, https://doi.org/10.1016/j.jenvman.2026.130294

Anthropogenic CO₂ emissions are intensifying climate change, creating an urgent need for scalable and efficient strategies to enhance the oceanic carbon sink. This study proposes and evaluates a new calcium–alkali coupling pathway in which the co-addition of Ca²⁺ and OH⁻ promotes the conversion of seawater dissolved inorganic carbon (DIC) into solid CaCO₃. This process perturbs carbonate-system equilibrium and subsequently drives additional atmospheric CO₂ uptake during system re-equilibration. Unlike conventional alkalinity-enhancement approaches that mainly retain absorbed CO₂ as dissolved bicarbonate and carbonate species, the pathway examined here emphasizes carbonate precipitation as a major mode of DIC removal. Laboratory experiments, mesocosm simulations, and a 1000 m³ offshore field demonstration in the southern Yellow Sea were conducted to assess carbon-removal efficiency and short-term environmental responses. Under a dosing scheme of 1.79 mmol Ca²⁺ and 3.58 mmol OH⁻ per litre of seawater, DIC in the 1000 m³ field system decreased by 1763 μmol kg⁻¹ and was converted into CaCO₃, corresponding to an estimated uptake of 77.6 kg atmospheric CO₂.

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Peer-reviewed Publications

Malakar et al. (2026): Stories of soil and sea: Comparing narratives of land- and marine-based carbon dioxide removal for responsible deployment

Yuwan Malakar, Kerryn Brent, Talia Jeanneret, Rod McCrea, John Gardner and Andrew Lenton, IN: Environmental Innovation and Societal Transitions, https://doi.org/10.1016/j.erss.2026.104851

Large-scale removal and storage of atmospheric CO₂ in land and ocean sinks is essential to meet Paris Agreement temperature goals, yet empirical evidence on how novel carbon dioxide removal (CDR) should be deployed responsibly remains limited. Using Australia as a case study, the authors provide one of the first empirical comparisons of stakeholder expectations for the responsible deployment of marine- and land-based CDR, comparing ocean alkalinity enhancement (OAE) and mineral carbonation (MC) to identify where governance priorities converge and where they diverge. Guided by responsible innovation and using Q methodology, they combined two rounds of interviews with a quantitative ranking exercise involving stakeholders across three Australian states.

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Peer-reviewed Publications

Campo et al. (2026): Comparative life cycle assessment of CO₂ removal solutions, including ocean liming, based on different energy sources and carbon storage methods

Francesco Campo, Giovanni Dolci, Mario Grosso, Phil Renforth, Mijndert van der Spek, Spyros Foteinis, Marta Manca Zeichen, Roberto Borghesi and Stefano Caserini, IN: International Journal of Greenhouse Gas Control, https://doi.org/10.1016/j.ijggc.2026.104742

The deployment of a wide range of carbon dioxide removal approaches is essential to limit global warming to well below 2 °C. Ocean liming (OL) combines CO₂ removal with the co-benefit of ocean acidification mitigation. This study evaluates four configurations of a process for removing atmospheric CO₂ including OL. They combine two energy sources (i.e. woody biomass and renewable electricity) to produce slaked lime, and two methods for the storage of CO₂ generated by the process (i.e. in underground geological formations and as bicarbonates in the sea via pH-equilibrated ocean alkalinization). The environmental impacts of the different configurations are evaluated through the life cycle assessment methodology.

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Peer-reviewed Publications

Marx et al. (2026): The Ecological Activity Index tool for mapping potential ecosystem exposure to ocean alkalinity enhancement

Lukas Marx, Jennie E. Rheuban, Daniel C. McCorkle, Christopher S. Murray, Yiming Guo, Zhaohui Aleck Wang, Anna P. M. Michel, Ke Chen, Heather H. Kim and Adam V. Subhas, IN: Communications Sustainability, https://doi.org/10.1038/s44458-026-00123-w

Ocean alkalinity enhancement is being explored to remove carbon dioxide from the atmosphere, but its interactions with marine ecosystems remain uncertain. Robust data-based baseline frameworks are needed to assess where and when ecosystems may be increasingly exposed to ocean alkalinity enhancement. Here the authors present the Ecological Activity Index (EAI) that integrates publicly available datasets on chlorophyll a, zooplankton, and fish larvae abundance, endangered species distributions and commercial fishing activity across the United States Northeast Shelf and Slope. This framework provides a spatially and temporally resolved measure of ecosystem activity and human use.

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Peer-reviewed Publications

Delval et al. (2026): Guidance on integrating marine environmental impacts of ocean alkalinity enhancement into life cycle assessment

Mona H. Delval, Patrik J. G. Henriksson, Paul Behrens, Laura Scherer, Pablo Trucco-Pignata, Patricia Grasse, Phil Renforth and Nils Thonemann, IN: The International Journal of Life Cycle Assessment, https://doi.org/10.1007/s11367-026-02707-z

Ocean alkalinity enhancement (OAE) is considered a promising marine carbon dioxide removal (mCDR) option and may contribute to climate change mitigation. Life cycle assessment (LCA) is used to assess OAE environmentally but faces limitations in capturing marine impacts. Improving the assessment of OAE in LCA requires a detailed understanding of its marine environment impact pathways to develop sub-compartmentalised and regionalised characterisation factors (CFs). The authors demonstrate how such pathways can be identified.
The authors build on Woods et al. (2021), who propose a qualitative framework to identify key components of impact pathways, and Richter et al. (2024), who provide guidance on framework development in a multidisciplinary context. The authors develop a methodological approach that allows to qualitatively identify the marine environmental impact pathways of OAE and determine which components are integrated in LCIA models or missing, as an initial phase toward developing CFs for life cycle impact assessment (LCIA).

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Peer-reviewed Publications

Musgrave (2026): How Uncertain Are Estimates of Marine Carbon Dioxide Removal? Insights from a Simplified Model

Ruth Musgrave, IN: Research Square, https://doi.org/10.21203/rs.3.rs-10006849/v1

Marine carbon dioxide removal (mCDR) approaches such as Ocean Alkalinity Enhancement (OAE) and Direct Ocean Removal (DOR) are necessarily evaluated using ocean models, yet uncertainties in model predictions remain poorly understood. Here, the author uses a one-dimensional ocean model to investigate the controls on uncertainty in atmospheric CO₂ drawdown in an abiotic system. The author shows that, within the first few years after deployment, estimates of carbon removal are highly sensitive to mixed-layer physical and biogeochemical properties, while longer-term uncertainties are dominated by vertical mixing, air–sea gas exchange and the depth of the initial deployment.

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Peer-reviewed Publications

Heede et al. (2026): Simulating enhanced ocean alkalinity experiments in a high-latitude fjord using nested ROMS simulations coupled with MARBL biogeochemistry – Preprint

Ulla K. Heede, Matthew C. Long, Alicia Karspeck, Scott Bachman, Nora Loose, Dafydd Stephenson, David T. Ho, Lennart Gerke, Tobias Koffman, Alice Benoit-Cattin, Sara Harðardóttir and Andreas Macrander, IN: EGUsphere (Preprint), https://doi.org/10.5194/egusphere-2026-2920

Ocean-based carbon dioxide removal (CDR) technologies have the potential to make significant contributions to climate change mitigation, yet more research is needed to deepen our understanding of their effectiveness and safety. One proposed method, ocean alkalinity enhancement (OAE), involves increasing seawater alkalinity to promote additional carbon uptake and long-term storage in the ocean. Ocean models are crucial tools to accompany OAE field trials and research, as alkalinity signals are rapidly diluted, and observations alone cannot capture the spatiotemporal scales at which interventions evolve. The C-Star open source regional ocean-biogeochemical modeling system is designed to support OAE research and quantification. Here, the authors present results from deploying C-Star in a nested regional modeling configuration established for Hvalfjörður, a fjord located in western Iceland. They compare the model solution with observations collected during a 2024 field campaign. These include repeated measurements of the fjord’s physical and chemical state, as well as a tracer release and sampling program used to assess the model’s ability to reproduce tracer transport and dispersal.

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