Biogeoscientists show evidence of 90 billion tons of microbial organismsexpressed in terms of carbon massliving in the deep biosphere, in a research article published online by Nature, July 20, 2008. This tonnage corresponds to about one-tenth of the amount of carbon stored globally in tropical rainforests. The authors: Kai-Uwe Hinrichs and Julius Lipp of the Center for Marine Environmental Sciences (MARUM) at University of Bremen, Germany; and Fumio Inagaki and Yuki Morono of the Kochi Institute for Core Sample Research at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) concluded that about 87 percent of the deep biosphere consists of Archaea. This finding is in stark contrast to previous reports, which suggest that Bacteria dominate the subseafloor ecosystem. To reach this conclusion, the researchers investigated sediment cores collected from several hundred meters beneath the seafloor of the Atlantic and Pacific Oceans and the Black Sea. The cored sediments included samples that were the result of research expeditions conducted by the Integrated Ocean Drilling Program (IODP).
According to co-author Prof. Kai-Uwe Hinrichs, a biogeochemist who led the research team, two main objectives were pursued: "We wanted to find out which microorganisms can be found in the seafloor, and how many of them are living down there."
For a long time, scientists believed that extreme conditions such as high pressure, lack of oxygen, and low supply of nutrients and energy would make deep, subseafloor environments inhabitable for any life form. Nonetheless, sea-going investigations have proven the existence of the deep biosphere.
"In general, life below the seafloor is dominated by minute monocellular organisms," explains co-author Julius Lipp, who has just completed his PhD on the subject. "According to our analyses, Bacteria dominate the upper 10 centimeters of the seafloor. Below this level Archaea appear to take over
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