How can krill, bug-like creatures the size of a pinkie, save our planet? A new study analyzed how these small but mighty open ocean organisms can draw down carbon from the atmosphere and store it deep in the ocean. 

Climate change is looming over the future. Critical action has been taken to reduce the amount of greenhouse gas that humans create such as carbon dioxide and methane. However, there’s still a need to draw down the carbon that has already been created and released during industrialization.   

Going hand in hand with emission reduction is the process of offsetting. This involves growing plants and restoring ecosystems that suck carbon from the atmosphere and store it in a way that keeps it from returning to the atmosphere for a long time. However, land is scarce. People need places to live and crop land to grow food, soaking up carbon from the atmosphere often isn’t a priority compared to other essential land uses. This is a massive problem. But research has shown that the ocean, and the tiny krill living there can help! 

Blue carbon refers to carbon storage in the ocean. Most blue carbon related projects focus on accessible coastal ecosystems like seagrass meadows, mangrove forests, and algae. But there are carbon sinks with more potential much further from our coastal waters.

Off shore, carbon dioxide in the atmosphere is grabbed by phytoplankton.  These almost microscopic single cell algae live in the open ocean, where they perform  photosynthesis and make the carbon usable for many organisms. Krill, then eat the phytoplankton, fueling their bodies, and then produce waste that falls to the ocean floor where it can stay for hundreds of years.

Taking a deep dive into this recent study published in Nature shows how those tiny pinkie-size krill can help tackle global climate change. Researchers from the United Kingdom and Denmark worked together to, well, estimate the amount of krill poo, otherwise known as “fecal pellets”. While there are other ways that these krill can move carbon to the depths of the Southern Ocean, such as molting (shedding their “skin” like a lizard) and dying, the researchers chose to focus on fecal pellets and use a database that includes 90 years of density data on Antarctic krill. This data was then used to determine calculations such as the depth of the Southern ocean, the amount of krill at different times of year, how many krill fecal pellets (and therefore carbon) actually becomes sequestered, and how much total carbon was sequestered by the krill in a given year. These questions and calculations elevate the importance of the humble krill.

What they learned is that krill poo really adds up. Atlantic krill sequester 20 million metric tons of carbon per year. This is approximately the same amount of carbon that 4 million cars produce in a year. And this estimate is conservative. Factoring in molting and migrations triples the calculated carbon sequestration abilities of the Atlantic krill (66 million metric tons of carbon). This more encompassing calculation shows that the krill beat out other  forms of blue carbon like seagrasses and mangroves. Krill then, are small but a mighty force to be considered in the fight against climate change and offsetting carbon emissions. 

This study makes several recommendations. Krill populations must be conserved, particularly in the face of overfishing. Since most krill aren’t caught for human consumption and instead are used in oils, health supplements, and farmed fish food, the fishery isn’t the doesn’t receive much thought or scrutiny. Researchers claim the fishery is unsustainably managed since it doesn’t take into account how krill drift around at sea and can move into unprotected waters easily. Sea ice melt and shifting ocean ecosystems; both of which are caused by climate change and human activities, are also threatening krill and their habitat. 

Despite the grim picture painted above, there are solutions to the conservation problem. Supporting krill populations could be considered for carbon credits (the system that large companies must use to be allowed to emit carbon). Projects that create protected zones for krill or provide incentives to krill fishers to reduce harvests could be used to generate carbon credits in the same way that planting mangroves or restoring seagrass can. Additionally, more attention should be brought to these open ocean ecosystems as an indispensable part of carbon sequestration. If something as small as krill can have such a large impact then other parts of the tangled web of nutrients that swirl in our oceans are worth a gander. Fighting climate change needs a fresh set of ideas and innovation. Perhaps when thinking of blue carbon… consider the krill.