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Breaking News- There’s a lot LESS life on Earth than we thought (intelligent and otherwise)

By Alaina G. Levine In my continuing mission to better understand what’s going on “down there”, specifically in the sediments under the sea in the planet’s basement, an exciting finding has caught my eye. According to a new paper published in the Proceedings of the National Academy of Sciences of the United States of America...

By Alaina G. Levine

In my continuing mission to better understand what’s going on “down there”, specifically in the sediments under the sea in the planet’s basement, an exciting finding has caught my eye. According to a new paper published in the Proceedings of the National Academy of Sciences of the United States of America (PNAS), there is a heck of a lot less life on Earth as we know it. For the first time, scientists have been able to create a clear map that predicts how many microbes are in subseafloor, which puts the estimate of Earth’s total number of microbes to be 50-78% lower, and consequently the total number of living biomass on the planet to be 10-45% lower, than previously believed.

As Steve D’Hondt, a co-author of the paper and professor in the Graduate School of Oceanography at the University of Rhode Island, recently told me, he and his team made the potentially game-changing discovery in an innovative manner – they demonstrated that the number of cellular creatures is linked to “everyday” processes in the ocean, that in turn are affected by surface activity. Specifically, D’Hondt and his colleagues recognized that there is a “strong correlation” between the number of microbes and sedimentation rate and distance from shore. By analyzing and factoring in sedimentation rates, distance to shore, and other factors like sea-surface chlorophyll concentration, they estimate that there are 2.9×10(to the 29) microbes living in the subseafloor.

In 1998 Whitman et al wrote that the predicted number of subseafloor microbes was around 35.5×10(to the 29). But as D’Hondt explained, Whitman and his group took samples from six sites that were in upwelling zones that contained an abundance of organic matter. More organic matter means there is more food for the little critters to enjoy, and thus one finds more cells in these areas. He also assumed the same depth of sedimentation everywhere. So according to the authors of this new paper, Whitman’s estimates were naturally skewed.

This new method takes into account that the sedimentation rates are not the same everywhere, and using statistical analysis offers the first clear map of the global distribution of subseafloor cells, predicting how many microbes actually live “down there”. These results and the method employed have more potential significant consequences – they can possibly be used to obtain a better estimate of the amount of carbon buried in the subseafloor, thus giving scientists a better grasp on the extent of, and subseafloor contribution to, the global carbon cycle, says D’Hondt.


Global distribution of subseafloor sedimentary cell abundance, Figure courtesy of Kallmeyer etal., PNAS

A. Geographic distribution of sedimentation rate. B. Geographic distribution of distance from shore. C. Geographic distribution of integrated number of cells (derived from b, m and sediment thickness). Dot colors indicate numbers of cells calculated for actual sites (log10 cells/km2)

Alaina G. Levine is a freelance science writer, professional speaker, corporate comedian, and President of Quantum Success Solutions, a leadership and career consulting enterprise. She can be contacted through her website at

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Meet the Author

Alaina G. Levine is science journalist, professional speaker, corporate comedian, and science and engineering careers consultant. As President of Quantum Success Solutions, a career consulting enterprise with a focus on advancing the professional development expertise of scientists and engineers, she has been advising emerging and established scientists and engineers about their careers for over a decade, and has personally consulted with hundreds of early- and mid-career scientific professionals. The author of over 100 articles pertaining to science, science careers and business in such publications as Science, Nature, Scientific American Online, IEEE Spectrum, New Scientist, and Smithsonian, she was recently named a Contributor to National Geographic, where she writes articles and blogs for NatGeo News Watch. Levine also writes the Careers Column for The Euroscientist and the Profiles in Versatility career column for the American Physical Society's national publication, APS News. Previously, she directed a master's program in science and business and taught entrepreneurship to science graduate students at the University of Arizona. She has given over 450 workshops and seminars around the country and in Europe. Levine holds degrees in mathematics and anthropology from the University of Arizona, studied abroad at the American University in Cairo as a DoD National Security Education Program/Boren Fellow, and pursued grant-funded research in cosmology and mathematics history. Recently, she was honored with a travel fellowship to cover the 62nd Lindau (Physics) Nobel Laureates Meeting in Lindau, Germany (which she used to cover the meeting for National Geographic and APS News), during which she broke the Higgs news for NatGeo. She also has been honored as a Logan Science Journalism Fellow at the Marine Biological Laboratory, Robert Bosch Stiftung Science Journalism Fellow and an Institutes for Journalism & Natural Resources Fellow. In addition, Levine is an award-winning entrepreneur, winning more than 20 business and leadership awards in under a decade, including being named one of the youngest YWCA Women on the Move winners; the Tucson Leader of the Year, an honor previously bestowed upon former US Surgeon General Richard Carmona; and a Tucson 40 Under 40 Leader, an honor she shared with former US Congresswoman Gabrielle Giffords. Read her complete bio at