The need to stop whaling has been given greater urgency by new research that shows Southern Ocean sperm whales 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, Southern Ocean sperm whales offset their carbon emissions by defecating – or pooing – iron on phytoplankton.

“Sperm whale poo is rich in iron, which stimulates phytoplankton to grow and trap carbon,” Ms Lavery said.

“When the phytoplankton die, the trapped carbon sinks to the deep ocean. 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,” she said.

It is estimated that the reduction in sperm whale populations by whaling has resulted in an extra 2 million tonnes of carbon remaining in the atmosphere annually.

“Other species of marine mammals may be capable of removing carbon from the atmosphere in the same way,” Ms Lavery said.

“And by fertilizing phytoplankton, sperm whales are increasing primary productivity in the ocean which may help to enhance fish stocks.

“My research is further evidence of the complex nature of the interaction between marine and terrestrial ecosystems. It makes a compelling case for an immediate ban on whaling.”

Ms Lavery’s findings appear in the latest edition of the prestigious Proceedings of the Royal Society, Biological Sciences.