Dead Whales Make for an Underwater Feast
When whales decay the seafloor, their enormous carcasses give life to mysterious worlds inhabited by an assortment of bizarre creatures.
Still, the discovery provides a provocative clue about how larvae find whalebones, since they may travel hundreds of miles before encountering another skeleton. "It's a pretty risky life history strategy to float around in the ocean waiting for a dead whale, which are few and far between," says Johnson. Scientists estimate that only one larva in thousands may successfully settle and reproduce. Studying more species will likely reveal a range of feeding strategies, Smith says, including generalists that feed on a variety of bones and specialists that feed only on whale carcasses.
Researchers are also trying to determine the relationship between whale fall organisms and those that thrive near deep-sea volcanoes. At least 12 species are common to both environments, including clams that rely on bacteria to mine sulfide seeps. "It's quite reasonable that some of these clams may use whale falls as dispersal stepping stones," says Smith.
As exotic and diverse as whale fall communities are proving to be, whaling in the 1800s and 1900s may have drastically reduced the number of carcasses that sank. "The decimation of whales during the last century also has consequences for an entire community of decomposer animals that live at the bottom of the ocean," says Vrijenhoek.
Many whale species are rebounding as a result of the International Whaling Commission's moratorium on commercial whaling, adopted in 1986, though humpbacks, fin, right, and blue whales are still well below their pre-whaling numbers (estimated to have been more than a million great whales). Biologists hope depleted populations will rebound to at least 50 percent of pre-whaling levels over the next few decades. Even if they do, Smith estimates 15 percent of whale fall specialist species may die out; there's usually a lag between habitat loss and consequent extinction. In the North Atlantic, where many whale populations hover at 25 percent of pre-whaling levels, Smith estimates that about one-third of whale fall specialists may have already been wiped out. "Removal of whales from the ocean will cause the extinction not only of whales, but likely dozens to possibly hundreds of deep-sea species that appear to rely on whale fall communities to complete their life cycle," explains Smith.
Despite the potential loss of species--some perhaps yet unknown--scientists expect to discover more connections between the behemoths above and their graveyards below. And, says Dahlgren, "For people looking for additional reasons to save the whales, this is one: a clear connection between the number of large-bodied whales and marine biodiversity."
|Brine Dining Scientists discovered Ruby, a 30-foot-long gray whale carcass, during a routine 9,800-foot-deep dive in Monterey Canyon with the remotely operated vehicle Tiburon. The carcass's name reflects red Osedax worms growing on the ribs and vertebrae, which deeply invade the bone and bone marrow to extract nutrients; small shrimplike crustaceans called lysianassid amphipods occur in the thousands at a rotting carcass, scraping away at the remaining flesh and biofilms that form on the bones;Osedax frankpressi, one of the first Osedax species discovered in 2002, are found only at 6,000 feet and deeper; among the first visitors at a new whale fall, the lithodid crab uses its pincers to tear small bits of flesh from the bone, while the slimy hagfish rasps away at fleshy tissues with its jawless mouth; a Pacific species of Greenland sleeper shark has been seen tearing large chunks of flesh from whale carcasses at depths of up to 3,000 feet.|