World Ocean Census - Extract 23 - Visualizing the invisible

13 July 2010

Technological advances have made it possible to identify new life-forms that only a few years ago were virtually impossible to see. A revolutionary new DNA technique, 454 tag sequencing, requires only small snippets of genetic code to identify an organism. With its help, Census scientists have revealed that the diversity of marine microbes may be some 10 to 100 times greater than expected.

By far the greatest part of this unexpected diversity is previously unknown, low-abundance organisms believed to play an important role in the marine environment as part of a “rare biosphere.”

These observations blew away all previous estimates of bacterial diversity in the ocean,” says Census scientist Mitchell L. Sogin, director of the Marine Biological Laboratory’s Josephine Bay Paul Center for Comparative and Molecular Biology and Evolution, at Woods Hole, Massachusetts, and leader of the Census project investigating microbes. “Just as scientists have discovered through ever more powerful telescopes that stars number in the billions, we are learning through DNA technologies that the number of marine organisms invisible to the eye exceeds all expectations, and their diversity is much greater than we could have imagined.”

Before this study, microbiologists had formally described 5,000 microbial “species,” but using this new DNA technique, scientists discovered more than 20,000 in a single liter (about a quart) of seawater.

Text and images reprinted with permission from World Ocean Census: A Global Survey of Marine Life by Darlene Trew Crist, Gail Scowcroft and James M. Harding Jr., Firefly Books, 2009

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