Parachuting allows krill to eat and run

Antarctic researchers have recorded a novel behavior in krill that may help regulate greenhouse gases. Antarctic krill, one of the largest animal resources on Earth, parachute into the deeper layers of the ocean many times a night and sequester large amounts carbon in the process.

The work is reported by Geraint Tarling of the British Antarctic Survey and Magnus Johnson of the Scarborough Centre of Coastal Studies, University of Hull.

Krill are shrimp-like crustaceans that live in the open ocean, mainly in large swarms. They reach particularly high numbers in Antarctica, where they form the staple diet of fish, penguins, seals, and whales. Like many other small pelagic animals, they perform daily vertical migration (DVM), in which they occupy the upper ocean layers at night to eat and the deeper layers by day to hide. Previous research has shown that this behavior may be a rapid means of transporting carbon to the ocean's interior. However, the amount sequestered was not considered to be large because it was assumed that DVM happened just once every 24 hours.

In the new work, the researchers found that krill are capable of many migrations each night. What is more, the downward migration may be particularly rapid as the krill fan out their swimming legs and enter a controlled descent, akin to parachuting. The behavior is most apparent when their stomachs are full and may be an effective means of getting out of harm's way when they can eat no more. It is estimated that Antarctic krill sequester 0.02 metric gigatons of carbon per year through this behavior, equivalent to the annual carbon emissions of 35 million cars.

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The researchers include Geraint A. Tarling of the British Antarctic Survey and Natural Environment Research Council in Cambridge, United Kingdom; Magnus L. Johnson of the University of Hull in Scarborough, United Kingdom.

Tarling and Johnson: "Satiation gives krill that sinking feeling." Publishing in Current Biology 16, R83-84, February 7, 2006. DOI 10.1016/j.cub.2006.01.044 www.current-biology.com


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