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Ocean graveyards tell whales of stories
Dead whales can tell plenty of tales, especially about life after death, according to oceanographer Craig Smith.
Whale corpses reveal volumes about the evolutionary biology of the deep sea, Smith said. And the historical documentation comes not a moment too soon.
"We know more about the surface of the moon than many areas of the deep sea," Smith said.
Smith was the first scientist to chance upon a whale corpse at the bottom of the ocean floor. The year was 1987. Since then, whale graveyards have supplied him with a wealth of information about deep-sea communities.
The sea life that is attracted to whale "falls," or corpses, is varied and abundant. On less than a square yard of a deceased whale recently found off the California coast, Smith and colleagues Dan Distel and Amy Baco counted 5,098 animals representing 178 species.
Smith's most recent finding indicates that the organisms found on or around whale falls are closely related to those found at hydrothermal vents and cold seeps. DNA analysis reveals that one type of mussel, the Idas washingtonia, found in abundance at whale falls, belongs to a subfamily of mussels previously thought to be restricted to hydrothermal vents.
"These mussels may have served as evolutionary stepping stones from shallow-water habitats to the extreme habitats of hydrothermal vents," Smith said in a recent interview. "In terms of the molecular clock, the organisms that live in hydrothermal vents are really not that old."
Hydrothermal vents are found primarily along tectonic plate junctions at temperatures ranging from 170 to 750 degrees Fahrenheit and pressures as high as 6,000 pounds per square inch. Scientists say organisms that dwell in such inhospitable habitats could offer vital clues to the origin of life.
Creatures that live in extreme environments derive their energy not from plants that grow in sunlight but from bacteria that feed on the sulphurous chemicals. The breakdown of chemicals in the sulphur-rich water by which the bacteria obtain their energy is referred to as chemoautotrophy.
As a dead whale sinks to the ocean floor, much of its remains decompose anaerobically, producing the same sulphurous chemicals that sustains the chain of sea life that exists at hydrothermal vents.
Previous studies conducted by Smith have shown that at least 11 species of sea life are found at hydrothermal vents and in whale-fall communities.
So far, Smith has studied two natural whale falls and three experimental falls planted off the coast of Southern California using a remotely operated vehicle and the research submersible ALVIN.
Smith is captivated by the sheer multitude of organisms he has found on the whale falls. "It is not uncommon to find new species in the deep sea, but usually you see only one or two of them," he said. "Finding them by the thousands is very exciting."
Smith's research is supported in part by the National Oceanic and Atmospheric Administration. His most recent findings are published in the Feb. 17 issue of Nature.
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