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For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Bill Noxon Contents of this News Tip:
"SEA SAWDUST" ENRICHES TROPICAL OCEANSOpen ocean waters in the tropics are often considered to be biological deserts - relatively unproductive areas with a scarcity of nutrients. But a paper appearing in the May 23rd issue of Science challenges this current thinking. Oceanographer Douglas Capone of the University of Maryland Chesapeake Biological Laboratory at Solomons, Maryland, presents findings that these vast oceanic regions are more productive than currently thought, and may, indeed, have a more important role in the uptake of atmospheric carbon dioxide. The National Science Foundation's divisions of ocean sciences and environmental biology supported studies by Capone and his colleagues (including Jon Zehr at the Rensselaer Polytechnic Institute in Troy, New York), of a widely distributed marine cyanobacteria called Trichodesmium, a blue-green alga known to mariners as "sea sawdust." This alga "blooms" on the ocean surface to resemble sprinklings of sawdust, which have been observed from the space shuttle and by color sensing satellites. Trichodesmium has the relatively rare capacity of being able to "fix" nitrogen, according to Capone. "It removes nitrogen from the atmosphere, converts it to ammonium, keeps some for its own nourishment, and releases the rest," he says. As trichodesmium grows, it removes carbon dioxide from the atmosphere via photosynthesis. The bottom line is that the world's oceans could have a much larger role in slowing down global warming. [Cheryl Dybas] INCREASED ULTRAVIOLET LIGHT HARMS ANTARCTIC ALGAEScientists have discovered that algae in Antarctica's Weddell Sea are extremely sensitive to increased ultraviolet radiation from the sun, especially ultraviolet-B (UV-B), let in by the ozone hole. Their discovery was made on a recent cruise aboard the National Science Foundation Foundation's (NSF) research icebreaker, the Nathaniel B. Palmer. Studies by Patrick Neale, biologist at the Smithsonian Institution's Environmental Research Center, show that UV-B exposure caused a greater reduction in photosynthesis in Weddell Sea algae than in algae from the Chesapeake Bay and other marine waters. Algae are the base of the aquatic food chain. Why Weddell Sea algae are more susceptible to UV-B is not clear. But Neale's data gathered aboard the NSF vessel show that UV-B has increased over Antarctica because of the seasonal depletion in the protective ozone layer there. Although the release of the man-made chlorofluorocarbons (CFCs) linked to ozone destruction has now been limited by international treaty, ozone depletion from CFCs already in the atmosphere is expected to continue for decades to come. Neale will head follow-up studies in both the Antarctic and Arctic oceans in 1997 and 1998. [Lynn Simarski] OCEAN DRILLING EXPEDITION HOPES TO SHED LIGHT ON SEA LEVEL CHANGESFor more than 35 million years, the waxing and waning of polar ice sheets is thought to have caused alternate falls and rises in sea level of as much as several hundred feet, as well as shifts of some coastlines by hundreds of miles. In recent geological times, between 19,000 and 6,000 years ago, the melting of vast glaciers across North America at the end of the Ice Age was attributed as the cause for sea level to rise about 400 feet to its present position. Scientists with the Ocean Drilling Program, funded in part by the National Science Foundation (NSF), will begin an expedition on June 21 to investigate the timing and magnitude of past sea-level changes, and discover how these changes may be related to ice sheet formation over the past 25 million years. Researchers will collect sediment and rock samples below the ocean floor about 80 miles east of Atlantic City, New Jersey, from the research vessel JOIDES Resolution. The scientists will drill several holes as much as half a mile deep at two sites near the edge of the continental shelf. The scientists will analyze layers of sediment retrieved in drill cores and try to document the precise timing and scale of the sea-level changes. Earth scientists estimate that global sea level has ranged up and down by several tens to hundreds of feet over parts of earth's history, but details have remained uncertain. According to the co-chief scientist Nicholas Christie-Blick of Columbia University's Lamont-Doherty Earth Observatory, this expedition will provide important new information that will fill gaps in existing knowledge of sea level shifts. [Cheryl Dybas]
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