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The big benefits of whale poo

G-Online

Research

Whale tail

Credit: Clipart

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They're big animals and they're playing a big part. According to new research from the Australian Antarctic Division (AAD), excrement from whales plays a vital role not only in holding together the aquatic food chain, but is also helping reduce CO2 levels in the Southern Ocean.

The study of whale waste was headed by Steve Nicol, of the AAD's Southern Oceans Ecosystems Program, and according to the researcher was "coined in the local pubs of Hobart". Conducted over the last 18 months, it involved the analysis of faecal samples from four species of baleen or great whales, to which family the humpback belongs.

The study group found whale droppings to be a key element in recycling iron in the ocean, promoting the growth of microscopic algae which in turn soak up carbon dioxide, reducing levels of the greenhouse gas in the upper reaches of the ocean.

"The baleen whales' faecal iron concentration is calculated to be about 10 million times that of Antarctic seawater," said Nicol. By making the iron available to help the algae thrive, the whales are also helping to boost the food supply for krill.

"The krill act as a nutrient package for the ocean, storing the iron in their bodies and keeping the iron close to the surface, which is of vital importance," Nicol said.

"If the iron were to sink down to the sea floor, it would no longer be available to phytoplankton [algae] who can only use it on the surface."

Nicol said that around 24 per cent of the total iron found in the Southern Ocean surface water - about 15,000 tonnes of it - is stored within the body tissues of krill.

One of the primary food sources for whales is these krill. "When whales consume the iron-rich krill, they excrete most of the iron back into the water, therefore fertilising the ocean and starting the whole food cycle again," Nicol said.

The study of whale droppings by the AAD is the first of its kind and has proven the long thought theory linking krill, whales and the recycling of iron.

"This monumental fertilising effort means the whales may have been responsible for recycling about 12 per cent of the current iron content in the surface layer of the Southern Ocean," Nicol said.

Australian waters are home to nearly 60 per cent of whales found on the planet. According to WWF, of the 13 baleen whale species, seven remain endangered or threatened.

Protection for these whales, and a general increase in the whale population, would not only be good news for whales but also good news for the planet, Nicol said.

"The ultimate conclusion is that more whales will mean more [algae], which equals more CO2 absorbed and more krill for whales to eat, starting the process over again."