 Scavengers Scamper to Food Fall
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Dec. 3, 2003 — What appeared to be just a fish carcass settling 2,000 feet below the waves was actually an extremely rare image of the dinner bell sounding for voracious bottom dwelling scavengers.
"Whenever there is some food available they consume and store as much as they can, then they disperse waiting for the next large food fall to come in — which can take some time," said Thomas Soltwedel of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. Soltwedel reports on the rare image of a "Large Food Fall" off the coast of Svalbard in last month's issue of the journal Oceanologica Acta.
Dedicated scavengers include fish, crustaceans and echinoderms (starfish and brittle stars), which can survive the long wait between meals by running their metabolisms at an economical, slow idle until the next fall of manna, as it were.
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When the carrion does reach the bottom, scavengers can apparently smell it from hundreds of and even thousands of yards away and come running, said deep sea biologist Jeff Drazen of the Monterey Bay Aquarium Research Institute in California. In experiments with deliberately placed carrion in the deep waters off California scavengers show up in minutes, he said.
In the case of the rare foot-long fish carcass seen by the Ocean Floor Observation System on the seafloor at the deep-sea long-term station Hausgarten west of Svalbard, Norway, it probably took only seven hours for scavengers to consume it completely, Soltwedel reported.
The fish fall is just a small example of what could, according to some researchers, account for as much as 30 percent of the biologically useful material that reaches deep ocean ecosystems, Soltwedel said.
But exactly how big a role food falls play, and how they change season-to-season and with upper ocean changes like El Nino, is very hard to say, Drazen said. That's because scavengers make such quick work of food falls that the chances of a researcher seeing one happen is very rare. "It's really difficult to study," he said.
If the food falls are, in fact, rare, scavengers might be specialists in slowing their metabolisms and storing energy reserves, Drazen said. That's something that could be of interest to medical science.
The food fall research is also helping to explain more macabre matters: such as why shipwrecks are always free of corpses or even skeletons. "Dead sailors don't last long," Drazen said. Even dead dolphins and whales only last a matter of days when they reach the bottom and are covered by swarms of hungry feeders at the last stop on the food chain.
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