By moving from the surface of the sea down to deeper layers, Antarctic krill transport carbon down from the surface to the depths of the ocean. Scientists from the British Antarctic Survey (BAS) and Scarborough Centre of Coastal Studies at the University of Hull have now discovered that Antarctic krill venture between the surface and the deep sea several times per night. Earlier, they were believed to do so only once per night. The more times they head for the deep with their bellies filled, the more carbon they will remove form the surface, so this is interesting news for anyone worried about too much carbon in the atmosphere and upper ocean. According to Dr Geraint Tarling from BAS, Antarctic krill transport an amount of carbon equivalent to the annual emissions of 35 million cars.

Krill swims to the surface to feed on phytoplankton (which must stay fairly close to the surface since they rely on photosynthesis) but they do not spend all their time close to the surface because that would make them easy targets for predators. Instead, krill regularly sink down to greater depths where the risk of being eaten is lower. When krill excrete carbon rich waste products at such depths, the waste will sink down to the ocean floor.

Other studies have shown that adding iron to the water could allow the krill populations to increase in size which would cause them to remove more CO2 from the atmosphere. Adding iron can also help trigger algae growth that further removes CO2 from the atmosphere and can help fight global warming. We do however know too little about the potential side effects of adding iron to the water to make it a viable alternative at this time.