Date of Original Version
The global geographic distribution of subseafloor sedimentary microbes and the cause(s) of that distribution are largely unexplored. Here, we show that total microbial cell abundance in subseafloor sediment varies between sites by ca. five orders of magnitude. This variation is strongly correlated with mean sedimentation rate and distance from land. Based on these correlations, we estimate global subseafloor sedimentary microbial abundance to be 2.9⋅1029 cells [corresponding to 4.1 petagram (Pg) C and ∼0.6% of Earth’s total living biomass]. This estimate of subseafloor sedimentary microbial abundance is roughly equal to previous estimates of total microbial abundance in seawater and total microbial abundance in soil. It is much lower than previous estimates of subseafloor sedimentary microbial abundance. In consequence, we estimate Earth’s total number of microbes and total living biomass to be, respectively, 50–78% and 10–45% lower than previous estimates.
Jens Kallmeyer, Robert Pockalny, Rishi Ram Adhikari, David C. Smith, and Steven D’Hondt. (2012). "Global distribution of microbial abundance and biomass in subseafloor sediment." Proceedings of the National Academy of Sciences, 109(40), 16213-16216. Available at: http://www.pnas.org/content/109/40/16213.abstract