Antarctic Krill Helps Fertilise Southern Ocean

The study, carried out by the British Antarctic Survey, Southampton University, Australian Antarctic Division and Oslo University, was reported in this months journal of Limnology and Oceanography.

An international team of researchers describe how Antarctic krill (Euphausia superba), once thought to live mostly in surface waters, regularly feed on iron-rich fragments of decaying organisms on the sea floor. They swim back to the surface with stomachs full of iron, releasing it into the water.

Antarctic krill is the staple diet for fish, penguins, seals and whales; and is harvested by commercial fisheries for human consumption.

Lead author from British Antarctic Survey, Dr Katrin Schmidt said: "We are really excited to make this discovery because the textbooks state krill live mainly in surface waters. We knew they make occasional visits to the sea floor but these were always thought as exceptional."

"What surprises us is how common these visits are – up to 20 per cent of the population can be migrating up and down the water column at any one time."

The scientists painstakingly examined the stomach contents of over 1000 krill collected from 10 Antarctic research expeditions. They found that the krill, caught near the surface, had stomachs full of iron-rich material from the seabed. The team also studied photographs of krill on the sea floor, acoustic data and net samples. All these provided strong evidence that these animals frequently feed on the sea floor.

This finding has implications for managing commercial krill fisheries and will lead to a better understanding of the natural carbon cycle in the Southern Ocean.

Ms Schmidt continued: "The next steps are to look at exactly how this iron is released into the water."

To view the paper please follow: Seabed foraging by Antarctic krill: Implications for stock assessment, bentho-pelagic coupling, and the vertical transfer of iron