Monday, April 26, 2010

Poo-tastic

Save the whales, save the planet. No longer mutually exclusive issues. More whales equals more whale poop, and now researchers from the Australian Antarctic Division (AAD) have taken a close look at that whale poop to study its affects on the ocean ecosystem. They have found that baleen whale poo contains large amounts of iron, 10 million times as much as seawater. Ah-ha! A great discovery as it applies to carbon cycling/storage/sequestration (call it what you want) in the oceans. Follow me here...

Iron is a source of food for phytoplankton.
Phytoplankton absorbs atmospheric carbon dioxide.
Phytoplankton is eaten by krill.
Krill is eaten by baleen whales.
Baleen whales excrete iron in their feces.

For a while, it has been suggested that whale poo contained high amounts of iron, but this is the first study to confirm that suggestion. The study also showed that the krill the whales are feeding on (DNA testing of the poo confirms that it contains a lot of krill) also contains large amounts of iron.

Recent geoengineering proposals have called for adding soluble iron to the ocean to seed this phytoplankton growth in order to sequester carbon. One of the reasons it hasn't happened yet is concerns over the consequences this seeding might have on the ocean ecosystem (think massive algae blooms, etc). According to this study, whale poop is an all natural way to reach this goal. True, we could still add iron to the ocean and we would see phytoplankton blooms (and the resultant krill blooms) which would absorb carbon dioxide. But without an increase in baleen whale populations you would not have a natural control mechanism in place.

Stephen Nicol of the AAD believes that before commercial whaling reduced whale populations to the brink, baleen whale feces may have accounted for approximately 12% of the iron in the Southern Ocean. Before commercial whaling, it is estimated that baleen whales consumed about 190 million tonnes of krill per year and produced 7600 tonnes of feces. That's a lot of iron-rich poo. So it stands to reason that if we allow whale populations to recover to pre-consumer whaling numbers then greater amounts of carbon will be sequestered in the oceans, fighting global warming.

The article appeared in Fish and Fisheries:
Nicol, Stephen et al. (2010) Southern Ocean iron fertilization by baleen whales and Antarctic krill. Fish and Fisheries: published online. (DOI: 10.1111/j.1467-2979.2010.00356.x)

and http://www.newscientist.com/article/dn18807-whale-poop-is-vital-to-oceans-carbon-cycle.html

(image from animal.discovery.com)
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