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| Credit: Stuart Halewood Underwater view of the giant kelp canopy in the Santa Barbara Channel. |
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| Scuba diver measures giant kelp biomass in permanent long-term underwater research plots. Credit: SBC LTER Site |
May 25, 2011
Marine scientists have a new view of the giant kelp in the Pacific Ocean--through a scuba mask and a satellite's "eye."
Forests of giant kelp, or Macrocystis pyrifera, are found in temperate coastal regions and are among the most productive ecosystems on Earth. In a melding of data from the beneath the waves and from the skies above, researchers have developed a method for studying how environmental factors affect the kelp forests.
The results have allowed scientists to look at changes in giant kelp across hundreds of square miles in California's Santa Barbara Channel over 25 years, from 1984 through 2009.
The findings are published in the current issue of the journalMarine Ecology Progress Series.
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| An underwater canopy: kelp plants grow toward the sea surface on strong, flexible stipes. Credit: SBC LTER Site In southern California, giant kelp is found primarily on shallow rocky reefs distributed in patches. The plants' numerous fronds extend upward in oceans and bays, forming a canopy at the surface. Giant kelp forms a dense floating canopy at the sea surface that's distinctive when viewed from above," write the scientists in their paper. "Water absorbs almost all incoming near-infrared energy, so the kelp canopy is easily differentiated using its near-infrared reflectance signal." The plants grow to lengths of more than 100 feet, at a rate of up to 18 inches per day. Giant kelp provides food and habitat for many ecologically and economically important near-shore fish and other species, says David Garrison, program director in the National Science Foundation's (NSF) Division of Ocean Sciences, which funded the research along with NSF's Division of Environmental Biology. The kelp is also an important source of food for many deep-sea species. Giant kelp that's uprooted from the seafloor is transported offshore into deeper waters, where it sinks and fuels deep-sea ecosystems with "phytodetritus." Through the recent research, scientists found that giant kelp growth in exposed areas of the Santa Barbara Channel is mostly controlled by large waves. The kelp's growth in more protected areas, however, is limited by low nutrient levels. |
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Information collected by scientists at the Santa Barbara Coastal Long-Term Ecological Research (LTER) site, one of NSF's 26 such LTER sites around the world, was added to the satellite data. Dan Reed of UCSB, a co-author of the paper and principal investigator of the Santa Barbara Coastal LTER site, has spent many hours as a scuba diver studying giant kelp. "The kelp occurs in discrete patches," he says, "but the patches are connected genetically and ecologically. Species that live in them can move from one patch to another. "Having the satellite capability allows us to look at how the different patches are growing, and to get a better sense of how they're connected," says Reed. "We can't get that information through diver plots alone." Continued large-scale and long-term observations are needed, he says, to understand how ecosystems--including giant kelp forests--might behave in a future climate. The fourth co-author of the paper is Philip Dennison of the University of Utah. The research was also funded by NASA. Related WebsitesNSF LTER Network: http://www.lternet.edu NSF Santa Barbara Coastal LTER Site: http://sbc.lternet.edu/ |
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