IF A whale breaks wind in the Southern Ocean and no one is around to hear it, does it make a sound?

This philosophical riddle could have been contemplated by Australian scientists while they collected whale waste as part of a study to determine if it could help ''fertilise'' the ocean and make it more productive.

Scientists from the Australian Antarctic Division, based in Hobart, have been testing the hypothesis that enormous amounts of iron excreted by whales is similar to liquid manure.

This fertiliser helps phytoplankton grow, which in turn helps support a wide number of marine species including those eaten by humans.

Whales take the iron into their systems by eating massive quantities of krill, a shrimp-like crustacean. But because whales produce blubber rather than muscle, they don't need iron in their diet - so it passes out in their excrement.