New research shows that sperm whales in the Southern Ocean play an important role in removing carbon from the atmosphere.
The study by Trish Lavery, a Flinders University PhD candidate, turns existing thinking on its head by demonstrating that, instead of increasing atmospheric carbon levels through respiration, the sperm whales offset their carbon emissions by defecating iron onto phytoplankton.
’Sperm whale faeces is rich in iron, which stimulates phytoplankton to grow and trap carbon,’ said Lavery.
’When the phytoplankton die, the trapped carbon sinks to the deep ocean,’ she added. ’By this process, sperm whales in the Southern Ocean remove approximately 400,000 tonnes of carbon from our atmosphere each year – more than double the amount of carbon they add by breathing out carbon dioxide.’
It is estimated that the reduction in sperm whale populations by whaling has resulted in an extra two million tonnes of carbon remaining in the atmosphere annually.
’By fertilising phytoplankton, sperm whales are increasing primary productivity in the ocean, which may help to enhance fish stocks,’ said Lavery.
Lavery’s findings appear in the latest edition of the Proceedings of the Royal Society, Biological Sciences.