Antarctic krill sequester similar amounts of carbon to key coastal blue carbon habitats
Nature Communications volume 15, Article number: 7842 (2024 ) Cite this article
The carbon sequestration potential of open-ocean pelagic ecosystems is vastly under-reported compared to coastal vegetation ‘blue carbon’ systems. Here we show that just a single pelagic harvested species, Antarctic krill, sequesters a similar amount of carbon through its sinking faecal pellets as marshes, mangroves and seagrass. Due to their massive population biomass, fast-sinking faecal pellets and the modest depths that pellets need to reach to achieve sequestration (mean is 381 m), Antarctic krill faecal pellets sequester 20 MtC per productive season (spring to early Autumn). This is equates USD$ 4 − 46 billion depending on the price of carbon, with krill pellet carbon stored for at least 100 years and with some reaching as far as the North Pacific. Antarctic krill are being impacted by rapid polar climate change and an expanding fishery, thus krill populations and their habitat warrant protection to preserve this valuable carbon sink.
Marine life has an important role in locking carbon away from the atmosphere in ocean systems, known as ‘blue carbon’. Coastal vegetation such as seagrass, mangroves and salt marshes dominate blue carbon research and policy1,2. Another important form of carbon sequestration which is ubiquitous in the global oceans is through the open-ocean biological carbon pump which stores carbon in the deep-sea3, and at present is not regularly framed in the blue carbon context. The biological carbon pump works by phytoplankton fixing dissolved CO2 into organic carbon during photosynthesis; when the cells die, they may sink to the deep ocean, along with the faecal pellets of phytoplankton grazers (zooplankton) and higher organisms such as fish4. If the sinking carbon is not remineralised, it may be sequestered for decades to centuries5, such that without this biological pump there would be 50 % more CO2 in the atmosphere6,7.
