Whale poo may hold key to krill mystery

Posted October 13, 2012 07:22:07

Scientists are examining the links between whale faeces and the food chain in the Southern Ocean.

There is a theory that the removal of large whales from the Southern Ocean over the past 150 years would lead to a population explosion of their main food source, krill.

Research scientist Stephen Nichol, from the Institute of Marine and Antarctic Studies, says there is not a lot of evidence that krill populations did increase as much as expected.

He says the same is true for other species further up the food chain.

"If you look at the population of seals, penguins they didn't seem to undergo massive changes," he said.

Mr Nichol says the reduction in iron-rich whale faeces and subsequent decrease in the amount of plant food available may be why krill populations did not explode.

"What whales did was to keep a lot of that iron in circulation," he said.

"And by keeping that iron in circulation, eating krill, defecating the iron rich faeces which produce more plant food which produced more krill you have a positive feedback loop."

But he says it will be complicated to test the theory.

"In the end it's probably going to come down to some mathematical modelling to look at all the links in the system and to see how they all interplay with each other," he said.

"So it's not a simple issue."

Topics: oceans-and-reefs, mammals---whales, animal-science, science-and-technology, environment, australia