Antarctic Krill locks similar levels of carbon as mangroves

As coastal vegetation such as seagrass or mangroves is critical in locking carbon from the atmosphere in water systems, researchers have given these ecosystems major attention.

However, another form of carbon sequestration is the biological carbon pump – storing the carbon in deep seas, which has gone unnoticed for a while. Without this biological pump, the atmosphere will witness a surge of Carbon Dioxide by 50%.

New research at Imperial College London demonstrates that Antarctic Krill has remarkable potential in carbon sequestration. These small marine crustaceans’ fecal pellets, molts, and carcasses can store as much carbon as coastal habitats like mangroves and seagrasses.

These pellets, molts, and carcasses can thoroughly sink Southern Ocean carbon fluxes into the deep waters.

Krill forms swarms of up to 30 trillion individuals, producing showers of large, fast-sinking fecal pellets and other waste products. After eating, this shower of krill feces locks carbon away from the atmosphere.

As fecal pellet carbon production flux has lower attenuation than the global average due to its fast-sinking nature, fecal pellets only need to sink to 200 m to start degrading and becoming part of water. This carbon would remain away from the surface ocean for 100 years.

To examine Antarctic Krill’s additional contribution to carbon sequestration, scientists used a published food-web model output to estimate the total carbon sequestered by plankton.

The estimation states that krill fecal pellets account for 12% of the total carbon sequestration from plankton in the Southern Ocean. This highlights the significant contribution of Krill to carbon storage.

More importantly, carbon transferred to the deep by Antarctic krill is transported to global oceans after bacteria break down the carbon-rich pellets into inorganic carbon.

“For the past decade, we have been piecing together the role krill have in carbon cycling, finally resulting in this amazing finding that krill, and their poo, store similar amounts of carbon as some coastal marine plants,” says Lead author Dr. Emma Cavan.

“This study shows how we as people are connected to a small creature in a remote location. We benefit from its actions in removing carbon but we also affect it through our own actions which drive climate change,” says Co-author Dr Simeon Hill.

Researchers used the social cost of CO₂ to convert krill fecal pellet carbon sequestration flux estimates into a single comparable metric: USD ($). This carbon sequestration is equivalent to $4-46 billion worth of carbon storage.

Microplastics found in coral skeletons and tissues: Antarctic Krill locks similar levels of carbon as mangroves

Krill in danger

Like other marine organisms, krill face human-induced challenges like global heating and overfishing.

Climate warming is reducing sea ice, with record Antarctic sea ice loss this year. This is a crucial habitat for larval krill. Moreover, mismanaged fishery adds to the temporal and spatial variability in krill ecology. Krill are also eaten by marine animals like whales, seals, and penguins.

“I hope we can now work towards conserving krill and their valuable Southern Ocean ecosystem with the same gumption as we are seagrasses and mangroves.” continued Dr. Cavan.

‘Marine identity’ can help society’s relationship with the ocean: Antarctic Krill locks similar levels of carbon as mangroves

Journal Reference

1. Cavan, E. L., Mackay, N., Hill, S. L., Atkinson, A., Belcher, A., & Visser, A. (2024). Antarctic krill sequester similar amounts of carbon to key coastal blue carbon habitats. Nature Communications, 15(1), 1-10. DOI: 10.1038/s41467-024-52135-6