Whale poop as carbon sink!

3 September 2010

The thought may be disconcerting but sperm whale feces are now recognized as one way Nature fights global warming. A study by Australian and German researchers has shown that the high iron content of whale excrement, released near the ocean’s surface, stimulates the growth of phytoplankton. In turn, these tiny aquatic plants take up CO2 from the atmosphere as they grow, trapping the carbon. Other marine mammals, like beaked whales, could similarly help offset greenhouse gases.

The new findings counter the theory that marine mammal respiration, which generates CO2, adds to atmospheric carbon in the Southern Ocean and decreases the efficiency of the biological pump. The researchers calculated that sperm whale exhalation releases only 200,000 tonnes of carbon per year whereas the 50,000 tonnes of iron defecated into the photic zone and stimulates the export of 400,000 tonnes of carbon each year to the deep sea, where it remains for hundreds to thousands of years. Thus the 12 000 sperm whales in the Southern Ocean act as a net carbon sink.

According to lead researcher Trish Lavery, if sperm whales had not been decreased from their historical levels by commercial whaling, they would pull an extra two million tonnes of carbon from the atmosphere every year.

Reference: Lavery, T.J. et al. 2010. Iron defecation by sperm whales stimulates carbon export in the Southern Ocean. Proceedings of the Royal Society.