Companies are scrambling to harness the power of Antarctic krill for health supplements, causing mounting concern over the ocean ecosystem among conservationists.

Krill, thought to be the most successful species on the planet, are tiny crustaceans found in every ocean.

In the vast Southern Ocean that encircles Antarctica, krill form the bottom of the food chain for much marine life, including the blue whale.

The total biomass of Antarctic krill is estimated to be 400 million metric tons -- roughly twice that of the human population.

For decades the Soviet Union was the only country to harvest krill. Krill mince became a Polish and German speciality in the 1970s, and in the Far East krill is still eaten, with a premium paid for females carrying extra fat.

But the biggest krill market has always been as animal feeds and aquaculture.

"If ever evidence were needed that we've fished our way down the food chain, then here it is," said Willie Mackenzie, of Greenpeace's oceans campaign. "Krill is the basis of the Antarctic food web, on which fish, seals, penguins and whales all rely."

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