Whale poo could help oceans absorb CO2

A humpback whale's tail comes out of the water during an excursion on the Les Ecumeurs on the St. Lawrence river at Les Escoumins, Quebec, August 13, 2009.

SYDNEY (Reuters) - Whale droppings have emerged as a natural ocean fertilizer which could help combat global warming by allowing the Southern Ocean to absorb more carbon dioxide, Australian scientists have found.

New research from the Australian Antarctic Division suggests whales naturally fertilize surface waters with iron-rich whale excrement, allowing the whole eco-system to send more carbon down into deep waters.

"The plants love it and it actually becomes a way of taking carbon out of the atmosphere," Antarctic scientist Steve Nicol told Reuters, adding the droppings appear as a plume of solids and liquids.

A larger population of baleen whales and krill would boost the productivity of the whole Southern Ocean ecosystem and could improve the absorption of carbon dioxide, blamed for global warming.

Iron is a limited micronutrient in the Southern Ocean, but recent experiments have found that adding soluble iron to surface waters helps promote much-needed phytoplankton algal blooms.

Iron is contained in algae in the surface waters where plants grow, but there is a constant rain of iron-rich particles falling into deep waters.

When krill eat the algae, and whales eat the krill, the iron ends up in whale poo, and the iron levels are kept up in surface waters where it is most needed.

"We reckon whale poo is probably 10 million times more concentrated with iron than sea water," Nicol said.

"The system operates at a high level when you have this interaction between the krill, the whales and the algae and they maintain the system at a very high level of production. So it's a self sustaining system."

Nicol said the idea to research whale droppings came from a casual pub chat among Antarctic scientists in Australia's island state of Tasmania.

He said it was not yet known how much poo it would take have a significant impact on the Southern Ocean.

(Reporting by Pauline Askin, editing by Miral Fahmy)