Dead whales may tell no tales, but they are an undersea encyclopedia to scientists who believe they may provide the building blocks for a variety of deepwater creatures. Craig Smith, a biological oceanographer at the University of Hawaii, and other researchers, have been conducting research on the ecology of whale falls – the whale corpses that drop to the bottom of the ocean – supported in part by the National Oceanic and Atmospheric Administration's National Undersea Research Program and its West Coast and Polar Regions Center at the University of Alaska Fairbanks.
Smith, Dan Distel, Amy Baco and other individuals have found that whale bones, along with sunken wood, could be a missing link in the introduction of new species near deep-sea vents, which can reach high temperatures and spew a chemical soup that many organisms find intolerable. The researchers' results will be published in the Feb. 17 issue of the journal Nature.
Smith and his colleagues are intrigued by the creatures that are attracted to whale corpses. One organism, a big, orange polychaete worm that looks like a furry centipede, can be found in such numbers around whale skeletons that one researcher says it looks like the bones are covered with a orange shag carpet. But scientists have yet to learn how these worms arrive at the carcasses, where they come from, and what their role is in consuming the massive amounts of organic material - often more than 30 tons - found in a whale fall.
Smith has studied two natural whale falls and three that were experimentally planted off the coast of southern California. Using a remotely operated vehicle and the research submersible ALVIN, Smith and his colleagues have visited the falls after short time interval, such as 10 and 120 days, as well as after one, three, five, and 10 years.
"We are able to observe the three stages of ecological succession, or community change, that the falls pass through," Smith said. "The first attracts scavengers, such as crabs, sharks, and fish that strip most of the soft tissue from the carcass in as little as four months."
During the second stage, furry worms and shrimp-like cumaceans take over. This lasts for perhaps a year, while the creatures consume the small particles of whale tissue that have been dispersed by scavengers over the nearby seafloor. The final stage is the longest, lasting years to decades. As the whale bones decay, they produce sulfide, which seems to support a rich variety of life, including tubeworms, mussels, and several species of clams. Baco and Smith found more than 30,000 animals totaling more than 200 species on a single skeleton, making whale falls one of the most species-rich "rocky" habitats in the deep sea.
The most recent research, to be published in Nature, indicates that the animals found at the whale falls are closely related to those found at hydrothermal vents and cold seeps. DNA analyses of one type of mussel, the Idas washingtonia, found in abundance at whale falls, indicates that this species belongs to a subfamily of mussels previously thought to be restricted to hydrothermal vents and cold seeps, said Smith. Earlier work by Baco, Smith, and others revealed that some of the sulfide-loving clams found on whale falls are in fact the same species as found at some vents and seeps.
Smith is a co-author on the Nature paper with Dan Distel and Wendy Morril from the University of Maine, Amy Baco from the University of Hawaii, and Colleen Cavanaugh and Ellie Chuang from Harvard University.
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