Steve D'Hondt, Ph.D.
University of Rhode Island
The Mass and Activity of Life in Subseafloor Sediment
Wednesday - May 13, 2009
Pacific Forum – 3:00 p.m.
Subseafloor sedimentary cell abundance and organic-fueled respiration vary geographically by orders of magnitude. They are highly correlated with several oceanographic properties. If these correlations hold throughout the world, organic-fueled subseafloor respiration is less than one percent of marine production, subseafloor sedimentary biomass is in the same order of magnitude as oceanic biomass, and Earth’s total biomass is about 1/3 smaller than the standard estimate.
Buried organic matter is the principal source of electron donors where respiration is high. However hydrogen from in situ water radiolysis may be the predominant electron donor in South Pacific gyre (SPG) sediment. The SPG community may be characteristic of subseafloor sedimentary communities throughout almost half of the ocean.
Anaerobic subseafloor sedimentary communities show the energetic limit to life to be extraordinarily low; their per-cell energy fluxes are orders of magnitude lower than in microbial cultures and surface environments.