Australian scientists have discovered that whale poo is not only helping ocean plant life to flourish, but also increasing the ocean's ability to absorb CO2.

Because whales' diets are made up largely of iron-rich krill (small crustaceans), their droppings are a great fertilizer for marine plants, helping them to grow like weeds (or algae).

The research suggests that if whale numbers grow, their droppings could help marine plant life flourish, thereby improving the ocean's ability to absorb carbon dioxide blamed for global warming.

Iron is a vital element in the production of marine plants, known as algae, which suck up carbon dioxide as they grow, although it is a scarce element in the "anaemic" Southern Ocean, said chemical oceanographer Andrew Bowie.

"One-third of the world's oceans are low in trace element iron," the researcher at the Antarctic Climate and Ecosystems Cooperative Research Centre told AFP.

Bowie said whales consumed several tonnes of krill, small shrimp-like crustaceans, each day and this found its way back into the ocean via emissions from the giant mammals.

He said while the researchers were pretty confident that whale poo would contain iron, they were surprised at the high concentration, about 10 million times that of Antarctic seawater.