Methane

Sediment

Phytoplankton

Organic matter

Ecology

Methanogenesis

Bacteria

Biology

Statistics

Geomorphology

Energy (signal processing)

Computer science

Earth science

Sulfate

Geology

Heterotroph

Oceanography

Paleontology

Genetics

Biogeochemical cycle

Organic chemistry

Mathematics

Photic zone

Environmental chemistry

Biomass (ecology)

Environmental science

Chemistry

Biosphere

Nutrient

Science Advances

Microbial cells buried in subseafloor sediments comprise a substantial portion of Earth's biosphere and control global biogeochemical cycles; however, the rate at which they use energy (i.e., power) is virtually unknown. Here, we quantify organic matter degradation and calculate the power utilization of microbial cells throughout Earth's Quaternary-age subseafloor sediments. Aerobic respiration, sulfate reduction, and methanogenesis mediate 6.9, 64.5, and 28.6% of global subseafloor organic matter degradation, respectively. The total power utilization of the subseafloor sediment biosphere is 37.3 gigawatts, less than 0.1% of the power produced in the marine photic zone. Aerobic heterotrophs use the largest share of global power (54.5%) with a median power utilization of 2.23 × 10-18 watts per cell, while sulfate reducers and methanogens use 1.08 × 10-19 and 1.50 × 10-20 watts per cell, respectively. Most subseafloor cells subsist at energy fluxes lower than have previously been shown to support life, calling into question the power limit to life.

Widespread energy limitation to life in global subseafloor sediments