Pooping for the Planet

As distasteful as it might sound, people can now count sperm whale excrement among the list of tools to fight global warming. According to a study in the Proceedings of the Royal Society B, these iron-rich droppings make the animals a carbon sink.

Sperm whales didn’t always have such a green reputation. Some scientists have pointed out that whales and other marine mammals in the Southern Ocean contribute a significant amount of carbon dioxide to the atmosphere through their respiration. But whales also release their feces close to the ocean’s surface, possibly promoting the growth of phytoplankton that remove atmospheric carbon dioxide.

A team calculated that the Southern Ocean’s 12,000 sperm whales excrete 50 tonnes of iron per year. The iron disposal causes 400,000 tonnes of atmospheric carbon to be removed annually, the researchers estimate, while the whales only respire 160,000 tonnes of carbon. Other marine mammals, such as beaked whales, could have a similar effect. – Roberta Kwok

Source: Lavery, T.J. et al. 2010. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean. Proceedings of the Royal Society B DOI: 10.1098/rspb.2010.0863.

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