Seven Worlds One Planet by Jonny Keeling & Alexander Scott

Author:Jonny Keeling & Alexander Scott
Language: eng
Format: epub
ISBN: 9781473531819
Publisher: BBC Digital
Published: 2019-10-09T23:00:00+00:00

The krill crisis

Antarctic krill are shrimp-like crustaceans about six centimetres long, but what they lack in size, they more than make up for in numbers. It is estimated that their combined weight, at any one time, is more than the total weight of the world’s human population. They are probably the most numerous animal species on the planet.

Antarctic krill are also a keystone species. Almost every animal living in the Antarctic depends on them. Even if it does not feed directly on krill, it will probably catch another that has, but our warming world could have an unforeseen impact on their populations.

During winter, krill migrate into the deep, and the sea ice traps substantial quantities of algae. When it melts, the algae bloom but, because the ice is melting earlier than usual, the krill are still deep down. If they do rise to the surface, they are in a slow metabolic state, and so they feed inefficiently. It means the algae die and sink to the seabed before the krill have had a chance to feed properly – a trophic mismatch.

Scientists have also noticed that most of the krill they see are generally longer and older adults. There are fewer juveniles, so recruitment is substantially less than it once was. Add this factor to the early ice melt and we have a potential serious population slump for every species relying on krill.

A third problem is that people are catching krill in huge quantities. Nowadays, fishing boats equipped with suction devises harvest more krill than they did previously, much of it as food for livestock or satisfying a demand for krill-based health products containing omega-3 fatty acids. For the moment, though, krill still gather together in astronomical numbers. A single swarm can have up to 30,000 animals per cubic metre, which makes them a primary target for baleen whales.

Krill is a shrimp-like crustacean and a keystone species in the Antarctic. It feeds almost everything – whales, seals, penguins and other seabirds, fish and many types of invertebrates.

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