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Permanent Carbon Sequestration in the Oceans

Carbon is permanently sequestered in the oceans through the following processes:

  1. Biological Pump: Marine organisms, like phytoplankton, absorb carbon dioxide (CO₂) during photosynthesis. When these organisms die, their remains, which contain carbon, sink to the ocean floor and contribute to the formation of sediment. This process is part of what’s called the biological pump 1.

  2. Carbonate Precipitation: In addition to organic carbon, carbon can also be sequestered in the form of inorganic carbonates, such as calcium carbonate (CaCO₃). These carbonates form through chemical processes in the ocean and contribute to the sediments that eventually become limestone and other carbonate rocks 2 3 4.

  3. Burial of Dissolved Inorganic Carbon (DIC): Some carbon in the ocean exists as dissolved inorganic carbon, which includes bicarbonate and carbonate ions. While most of this carbon remains in the water column and is part of the carbon cycle, a portion can also become buried in sediments over geological timescales 5.

  4. Hydrothermal Processes: In certain areas of the ocean, especially near mid-ocean ridges, hydrothermal vents can cause carbon to be sequestered in the ocean crust through reactions with basalt. This process can also lead to long-term or permanent carbon sequestration 6 7.

While other forms of carbon storage in the ocean, like dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC), are significant, they are not typically considered permanent as they can eventually re-enter the carbon cycle. Permanent sequestration is most commonly associated with the processes that result in the burial of carbon in sediments or its incorporation into stable geological formations.

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Footnotes​

  1. Siegel, D A., DeVries, T., Cetinić, I., & Bisson, K. (2023, January 16). Quantifying the Ocean's Biological Pump and Its Carbon Cycle Impacts on Global Scales. Annual Reviews, 15(1), 329-356. https://doi.org/10.1146/annurev-marine-040722-115226 ↩

  2. Renforth, P., & Henderson, G M. (2017, July 27). Assessing ocean alkalinity for carbon sequestration. Wiley, 55(3), 636-674. https://doi.org/10.1002/2016rg000533 ↩

  3. Zhu, T., & Dittrich, M. (2016, January 20). Carbonate Precipitation through Microbial Activities in Natural Environment, and Their Potential in Biotechnology: A Review. Frontiers Media, 4. https://doi.org/10.3389/fbioe.2016.00004 ↩

  4. Moore, C H., & Wade, W J. (2013, January 1). The Basic Nature of Carbonate Sediments and Sedimentation. Elsevier BV, 3-21. https://doi.org/10.1016/b978-0-444-53831-4.00001-x ↩

  5. Emerson, S., & Hedges, J I. (2008, April 24). Chemical oceanography and the marine carbon cycle. https://doi.org/10.1017/cbo9780511793202 ↩

  6. Goldberg, D., Takahashi, T., & Slagle, A L. (2008, July 22). Carbon dioxide sequestration in deep-sea basalt. National Academy of Sciences, 105(29), 9920-9925. https://doi.org/10.1073/pnas.0804397105 ↩

  7. Haas, H D., Weering, T C V., & Stigter, H D. (2002, March 1). Organic carbon in shelf seas: sinks or sources, processes and products. Elsevier BV, 22(5), 691-717. https://doi.org/10.1016/s0278-4343(01)00093-0 ↩