Fallout feast: vent crabs survive on victims of plume.In an undersea twist on the family dog appearing just as pizza slips off a plate, crabs at Taiwan's shallow-water hydrothermal vents swarm to feast on the gentle rain of plankton plankton: see marine biology. killed whenever toxic plumes shoot straight up from the vents. Peter Ng of National University of Singapore and his colleagues puzzled over what bonanza could support the many crabs observed at shallow vents around Kueishan Island in northeastern Taiwan. Hazardous scuba scuba: see diving, deep-sea. dives to watch the crabs plus dissections of captured specimens led them to propose the plume-kill scenario in the Dec. 23/30, 2004 Nature. "I was completely surprised" by their finding, says deep-water oceanographer Cindy Van Dover of the College of William and Mary in Williamsburg, Va. "It makes sense, once you think about it." Hydrothermal vents hydrothermal vent, crack along a rift or ridge in the deep ocean floor that spews out water heated to high temperatures by the magma under the earth's crust. Some vents are in areas of seafloor spreading, and in some locations water temperatures above 350°C; (660°F;) have been recorded. The vents' hot springs leach out valuable subsurface minerals and deposit them on the ocean floor. releasing sulfurous 1. Of, relating to, derived from, or containing sulfur, especially with valence 4. 2. Characteristic of or emanating from burning sulfur. In the late 1990s, when Taiwan opened access to Kueishan Island, scientists moved in to study vents only 8 to 20 meters below the surface--within scuba diving range. The intense concentrations of sulfur compounds "make it very unpleasant," says Ng. "The plumes are also very hot, so one has to be careful not to get scalded scald (skawld) to burn with hot liquid or steam; a burn so produced. scald (skôld) v. To burn with a hot liquid or steam. n. :' The area's high seismic activity keeps the seafloor unstable, and frequent landslides on a cliff on the nearby shore drop boulders into the water. A body injury caused by scalding. While diving, coauthor Ming-Shiou Jeng of Academia Sinica in Taipei discovered that thousands of about 2-centimeter-wide brown crabs (Xenograpsus testudinatus), but no larger organisms, lurk at these vents. On a serendipitously timed dive, Jeng saw that the crabs swarmed when the tides and currents permitted the plume to rise vertically. When the plumes trail sideways, the plankton they kill drop far from the crabs. When the scientists dissected crabs, they found that the creatures had been feasting on tiny copepods co·pe·pod (k ![]() p -p d, which could have come from overhead. During repeated dives to the vents, if visibility was good, Jeng would even see a "snow" of small fish and some other creatures killed by the toxic plume. The feasts remind Verena Tunnicliffe of the University of Victoria in British Columbia of reports from other kinds of danger zones. "Real nasty places to live," says Tunnicliffe, can offer opportunities, such as nutrients, to animals that can survive there. The idea of plume-kill feasts supporting the crabs "does sound plausible to me,' says James Childress of the University of California, Santa Barbara, who studies deep-sea vent crabs. |
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