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Friday, February 18, 2005

Another undersea community discovered

Communities of living things near the mid-ocean rifts have been discovered, and are reasonably well known (see here for my review of a documentary about them). Another undersea community has been discovered. This is the community of organisms that depend on whale carcasses.

Amanda Haag wrote "Whale Fall," in the February 10, 2005, 433:566-7, issue of Nature. Haag is a science writer, and has not done the work herself, but she reports it well. She writes that "Scientists now estimate that a whale-fall community can survive for up to a century by sucking fats and sulphides from these bones." (p. 566) (See here for another article about whale fall communities.)

Scientists believe that as many as 39 species are suited to profit from whale carcasses that fall to the bottom of the sea. Haag describes a newly discovered worm, Osedax, the most fully. This creature "has a clever metabolic strategy. With no mouth, stomach or eyes, Osedax has evolved a root system to excavate the fat out of whale bones. The worms tunnel into the bones with their green, fleshy roots and turn them into 'Swiss cheese'. . ." (p. 567)

Since whale populations have been seriously depleted by human exploitation, there would be expected to be considerably fewer whale fall communities now than, say, a century ago. Because of this scarcity, there aren't many such communities to study. Scientists are sinking dead beached whales, so as to increase the number of communities that can be studied. Haag writes that it may take up to 3000 kilograms of scrap metal to sink a whale carcass.

It is supposed that there are not as many species of whale fall-dependent organisms as there were in the past, because of the depletion of their habitat.

As in the rift communities, one question that hasn't been completely answered is that of how the whale fall organisms disperse to new locations.

Unlike the rift communities, whale fall communities depend on photosynthesis. Most or all of the whale's body has come from consuming plants, or animals that eat plants.

What else don't we know, even here on earth?

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