WHALE FALL the Fatty Bones of Dead Whales Provide Rich Pickings for Creatures on the Sea Floor

MBARI

WHALE FALL The fatty bones of dead whales provide rich pickings for creatures on the sea floor. Amanda Haag meets the scientists who go to extreme and unpleasant lengths to study the unique ecosystems on these corpses. n 1987, a manned submersible called years on the soft tissue of a single whale, might prove useful in cold-water detergents. Alvin was making a routine dive along the depending on its size. As bits of whale tissue For scientists such as Smith, studying Imuddy plains of the deep sea when its spread around the carcass, the enriched whale falls presents some inherent chal- pilot spotted what he thought was the fos- seafloor sediment provides nutrition for lenges — not least of which is finding a body silized remains of a dinosaur. Instead of an opportunistic worms and crustaceans. As to examine. Many whales die when female exotic underwater beast, it turned out to be anaerobic bacteria further the whale’s whales or newborns, stressed by the process the 21-metre-long skeleton of a blue whale. decomposition, they create a sulphide-rich of birth, make their annual migration. In the But atop this mass of bones the pilot did environment allow- Pacific, for example, there are often casual- find something exotic: a carpet of creatures, “Whale bones are ing sulphur-loving ties on the long treck north to Alaska from including bacteria and worms, similar to hanging in our cold creatures to move in. birthing grounds along the Baja Peninsula of those found on the flanks of underwater room with cultures Worms, clams and Mexico. Although whale carcasses tend to volcanoes. of bacteria stuck all mussels, to name but accumulate along these migratory paths, The Alvin team had happened upon what over them.” a few, all take up resi- they fall at random locations and can be have since become known as ‘whale falls’ — — Thomas Dahlgren dence, each getting spaced very far apart. communities of creatures that thrive among their metabolic fix the sulphur-laden ooze of decaying whales. from the chemical energy provided by the Body hunt Just as windfalls deliver a sudden bounty of fat-rich marrow in whale bones1. “They’re hard to find because you can’t just ripened fruit, whale falls see the death of a Such complex communities have not follow a particular geological feature on the whale bring a host of nutrients to the sea been reported on the bones of other marine sea floor and drive up to them like you can floor. The falls are few and far between, and mammals, says Craig Smith, a whale-fall with hydrothermal vents,”says Smith. In the difficult to track and study, but researchers expert from the University of Hawaii at early 1990s, the US Navy surveyed more are learning ever more — sometimes Manoa.This is probably because whale bones than 300 square kilometres of the Pacific sea through extreme measures — about the new are so much larger and fat-rich,he says. floor in search of a lost missile and found species to be found among the remains. Scientists now estimate that a whale-fall eight whale skeletons. The navy contacted Some 39 of the species discovered so far are community can survive for up to a century Smith, but didn’t take exact coordinates of thought to be especially suited or even by sucking the fats and sulphides from these where the skeletons were located. When unique to this environment. bones. The bacteria that make their home Smith’s team returned to the site, it could In the barren depths of the open ocean, a on whale falls are so good at degrading find only one of the eight. fallen whale carcass is a veritable feast. Scav- fat in cold waters that the biotechnology So far, ten natural whale falls have been engers such as sleeper sharks, hagfish and company Diversa in San Diego, California, investigated by the dozen or so scientists squat lobsters can dine for months to many is looking to see whether their enzymes who study them. And another 20 have been

weigh it down with up to 3,000 kilograms of within their tissues to digest fats and oils Food for thought: the scrap metal, from train wheels to anchor from the bone marrow. Although the bac- decomposing carcass of a chains. It can take two days to get a whale teria are similar to those found in oil slicks, whale can support a whole from the shore to the sea floor — and all this sort of microbe has never been found host of organisms. those involved agree that it is a highly in a symbiotic partnership with another unpleasant process. “We often throw away creature before. our clothes because you can’t get the So far,researchers have found five species smell out,”says Smith.“It’s one of the hazards of Osedax — four in the Pacific and, most of the job.” recently, one in the Atlantic, implying that Researchers have so far sunk about 20 the worms have a worldwide distribution. whales this way. They return to these whale Two of the species have a matriarchal society falls regularly to monitor the colonization of of sorts, in which all of the female members organisms on the remains. Smith’s group are about the length of an index finger, placed a time-lapse camera on one carcass, and the males are mere microscopic threads which took pictures more-or-less continu- that live inside the ously for eight months. Others send sub- “We often throw females’ oviducts. A mersibles to the sites, which can pick up rib away our clothes single female can bones and vertebrae and bring them to the because you can’t hold up to 111 males. surface with the communities still alive and get the smell out. Another oddity is mostly intact. It’s one of the a whale-fall worm Thomas Dahlgren, a population gen- hazards of the job.” nicknamed ‘Pinky’, eticist at the Tjärnö Marine Biological Lab- — Craig Smith which at first evaded oratory in Strömstad, Sweden, has been identification by its fortunate enough to sink a whale researchers, including Greg Rouse at the near his lab. The whale falls that University of Adelaide in Australia. After have been studied off the coast of much head-scratching, it became apparent MBARI California tend to be 1,200–3,000 that Pinky was just a polychaete worm — metres deep and at least half-a- the class that includes ragworms and lug- day’s cruise away from the nearest worms — albeit much larger than its shal- lab; Dahlgren’s whale is 125 low-water relatives. “Pinky is a giant,” says metres deep and just half an hour Rouse.“He’s more than one centimetre long, from his office. “We’re not stuck whereas his relatives are of the order of a on a ship in the Pacific couple of millimetres. Pinky’s also quite fat.” bobbing around with a The worm measures a whopping one to two G. ROUSE limited time until millimetres across. the cruise is over,” Many mysteries about the whale-fall says Dahlgren.He communities remain. For one thing, scien- and his team can tists are trying to find out how larvae from sample the whale whale-fall organisms that are spawned into

fall as often as the water live long enough to find their way C. R. SMITH once a week. to another bone.“It is really clever. We don’t Dahlgren’s lab know how they do it,but they do it,”says Paul also keeps whale Tyler, a deep-sea ecologist at the Southamp- bones with live speci- ton Oceanography Centre,UK. mens in a seawater tank. Scientists guess that the creatures in Unlike creatures found at whale-fall communities probably date back hydrothermal vents, which can some 35 million years. But in the past few only survive at the high pressures centuries they have faced a serious threat. found at the bottom of the deep Smith estimates that whaling in the 1800s sea, some whale-fall organisms and 1900s reduced whale-fall habitat by up seem to adapt quite well to life on to 95%, potentially wiping out up to half of Sinking feeling: intrigued by Osedax,a newly the surface.“Whale bones are hanging in our the species that were specialized to live on discovered genus of bone-eating worms (top and cold room with cultures of these whale bac- whale carcasses in some ocean basins3.Each inset), and other odd creatures, scientists tow teria stuck all over them,”says Dahlgren. time a whale was dragged aboard a ship, it dead whales to the deeps for study. not only depleted the live stocks, but also Crunch time those of the dead falling to the sea floor. It’s sampled accidentally by trawling fishermen. Such research has unveiled a number of not just the whales that needed saving, notes In an attempt to increase these numbers, strange creatures. Perhaps the prize find so Smith. If hunting had continued apace it whale-fall researchers have resorted to sink- far is a newly described worm genus, might have wiped out not only the great ing beached dead whales. But sinking a four- Osedax2 — Latin for ‘bone-devourer’ — whales,but Pinky too. ■ tonne juvenile grey whale, or a 35-tonne which has a clever metabolic strategy. With Amanda Haag is a freelance science writer based adult,is a major undertaking,says Smith. no mouth, stomach or eyes, Osedax has in Boulder, Colorado. When researchers get a call about a evolved a root system to excavate the fat 1. Smith, C. R. & Baco, A. R. Oceanogr. Mar. Biol. Annu. Rev. 41, washed-up whale, they mobilize their teams out of whale bones. The worms tunnel into 311–354 (2003). and ships.By the time they reach the whale it the bones with their green, fleshy roots 2. Rouse, G. W., Goffredi, S. K. & Vrijenhoek, R. C. Science 305, 668–671 (2004). is often bloated with gases from decomposi- and turn them into “Swiss cheese”, says 3. Smith, C. R. in Whales, Whaling and Ocean Ecosystems (ed. tion. To get it to sink, the scientists have to Smith. The worms then rely on bacteria Estes, J.) (Univ. California Press, Berkeley, in the press).