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Carbon from marine snow and other falling biomass and POC can be sequestered permanently when it is buried and remains under the ocean floor, stored in shells formed by living creatures that are ultimately buried, or in other ways.

The ocean plays a crucial role in the global carbon cycle, acting as a significant sink for atmospheric carbon. The precise rate of carbon absorbed by the oceans which is permanently sequestered — as opposed to active in the carbon cycle — is uncertain, but very low, and various mechanisms have been identified123.

These mechanisms include the formation of calcium carbonate skeletons by marine organisms, which contributes to long-term carbon storage as these structures accumulate and are buried over geological time scales2. Additionally, the process of microbial degradation and transformation of organic matter into stable dissolved organic carbon molecules also plays a significant role in sequestering carbon within marine systems, with a substantial portion of this dissolved organic carbon being capable of persisting in the ocean for thousands of years4.

Moreover, diverse seafloor communities can enhance the conversion of captured carbon into stable sedimentary forms, thus potentially increasing the overall sequestration capacity of these crucial ecosystems3.

The biological pump, driven by the photosynthetic fixation of CO2 and the subsequent export of particulate organic carbon into the deep ocean, is recognized as a key mechanism for carbon sequestration1. This process results in less than 0.1% of primary production being ultimately buried as particulate organic carbon, with the remainder primarily being respired back into the atmosphere as CO2, highlighting the complexity of carbon dynamics within marine ecosystems5. The export of organic carbon through the biological pump, however, is only one pathway by which carbon can be sequestered in the ocean, with other mechanisms, such as the formation of calcified structures and the microbial carbon pump, also playing important roles524.

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Footnotes​

  1. Feely, R. A., Sabine, C. L., Takahashi, T., & Wanninkhof, R. (2001). Uptake and storage of carbon dioxide in the ocean: The global CO2 survey. Oceanography, 14(4), 18-32. https://doi.org/10.5670/oceanog.2001.03 ↩ ↩2

  2. de Haas, H., van Weering, T. C. E., & de Stigter, H. (2002). Organic carbon in shelf seas: Sinks or sources, processes and products. Continental Shelf Research, 22(5), 691-717. https://doi.org/10.1016/s0278-4343(01)00093-0 ↩ ↩2 ↩3

  3. Morley, S. A., Souster, T., Vause, B. J., Gerrish, L., Peck, L. S., & Barnes, D. K. A. (2022). Benthic biodiversity, carbon storage, and the potential for increasing negative feedbacks on climate change in shallow waters of the Antarctic Peninsula. Biology, 11(2), 320. https://doi.org/10.3390/biology11020320 ↩ ↩2

  4. Jiao, N., & Zheng, Q. (2011). The microbial carbon pump: From genes to ecosystems. Applied and Environmental Microbiology, 77(21), 7439-7444. https://doi.org/10.1128/aem.05640-11 ↩ ↩2

  5. Siegel, D. A., DeVries, T., Cetinić, I., & Bisson, K. (2023). Quantifying the ocean’s biological pump and its carbon cycle impacts on global scales. Annual Review of Marine Science, 15(1), 329-356. https://doi.org/10.1146/annurev-marine-040722-115226 ↩ ↩2