Sperm whale faeces may help oceans absorb carbon dioxide from the air, scientists say.
Australian researchers calculate that Southern Ocean sperm whales release about 50 tonnes of iron every year.
This stimulates the growth of tiny marine plants - phytoplankton - which absorb CO2 durin photosynthesis.
The process results in the absorption of about 400,000 tonnes of carbon - more than twice as much as the whales release by breathing, the study says.
