TY  - JOUR
A1  - Kallmeyer, Jens
A1  - Pockalny, Robert
A1  - Adhikari, Rishi Ram
A1  - Smith, David C.
A1  - D'Hondt, Steven
T1  - Global distribution of microbial abundance and biomass in subseafloor sediment
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - 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 center dot 10(29) cells [corresponding to 4.1 petagram (Pg) C and similar to 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.
KW  - deep biosphere
KW  - cell enumeration
KW  - global microbial biomass
KW  - subsurface life
Y1  - 2012
U6  - https://doi.org/10.1073/pnas.1203849109
SN  - 0027-8424
VL  - 109
IS  - 40
SP  - 16213
EP  - 16216
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Roy, Hans
A1  - Kallmeyer, Jens
A1  - Adhikari, Rishi Ram
A1  - Pockalny, Robert
A1  - Jorgensen, Bo Barker
A1  - D'Hondt, Steven
T1  - Aerobic microbial respiration in 86-million-year-old deep-sea red clay
JF  - Science
N2  - Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O-2 liter(-1) year(-1) near the sediment-water interface to 0.001 micromoles of O-2 liter(-1) year(-1) at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10(-3) femtomoles of O-2 cell(-1) day(-1) 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux.
Y1  - 2012
U6  - https://doi.org/10.1126/science.1219424
SN  - 0036-8075
VL  - 336
IS  - 6083
SP  - 922
EP  - 925
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  -