Whale poo helps offset carbon footprint

Southern Ocean sperm whales offset their carbon footprint by defecating, scientists said on Wednesday, releasing tons of iron a year that stimulates the growth of phytoplankton which in turn absorb carbon dioxide.

Each whale releases about 50 tons of iron a year after digesting the fish and squid they hunt. Their natural fertilization stimulates the process of photosynthesis, removing the equivalent carbon emissions from 40,000 cars each year. The cetaceans have been previously fingered as climate culprits because they breathe out carbon dioxide (CO2), the commonest greenhouse gas.

An estimated 12,000 sperm whales that inhabit the Southern Ocean absorb about 400,000 tons of carbon each year, twice the amount they release by breathing, said scientists from Flinders University in South Australia.

"They eat their diet, mainly squid, in the deep ocean, and defecate in the upper waters where phytoplankton can grow, having access to sunlight," marine biologist Trish Lavery, who led the scientific study at Flinders University, said in a statement.

"Sperm whale poo is rich in iron, which stimulates phytoplankton to grow and trap carbon. When the phytoplankton die, the trapped carbon sinks to the deep ocean," Lavery said.

"They've well and truly bypassed being carbon neutral. They've actually gone one step further," she said. The whale study was published in the Royal Society's biological research journal, Proceedings of the Royal Society, Biological Sciences.

Before industrial whaling, the population of this species was about 10 times bigger, which meant around two million tons of CO2 were removed annually, said the paper.

The Southern Ocean is rich in nitrogen but poor in iron, which is essential for phytoplankton. The scientists suspect that because sperm whales cluster in specific areas of the Southern Ocean there is a clear link between food availability and cetacean feces.

This could explain the "krill paradox," they believe. Researchers have previously found that when balleen whales are killed, the amount of krill in that sea area declines, which thus affects the entire food chain.

Source:
Reuters, "Whale poo helps offset carbon footprint", accessed June 16, 2010
Yahoo News, "Faecal attraction: Whale poop fights climate change", accessed June 16, 2010