Abstract
Groundwater ecosystems are globally wide-spread yet still poorly understood. We investigated the age, aqueous geochemistry, and microbiology of 138 groundwater samples from 87 monitoring wells (<250m depth) located in 14 aquifers in the Canadian Prairie. Geochemistry and microbial ecology were tightly linked revealing large-scale aerobic and anaerobic hydrogen, methane, nitrogen, and sulfur cycling carried out by diverse microbial communities. Older groundwaters contained on average more cells (up to 1.4×107/mL) than younger ground-waters. Organic carbon-rich strata featured some of the highest abundances, challenging current estimates of global groundwater population sizes. Substantial concentrations of dissolved oxygen (n=57; 0.52±0.12 mg/L [mean±SE]; 0.39 mg/L [median]) in older groundwaters could support aerobic lifestyles in subsurface ecosystems at an unprecedented scale. Metagenomics, oxygen isotope analyses and mixing models indicated that microbial “dark oxygen” contributed to the dissolved oxygen pool in subsurface ecosystems commonly assumed to be anoxic.
Publisher
Cold Spring Harbor Laboratory
Reference107 articles.
1. I. A. Shiklomanov , in Water in Crisis - A Guide to the World’s Fresh Water Resources, P. H. Gleick , Ed. (Oxford University Press, Oxford, UK, 1993), pp. 13–24.
2. Prokaryotic and Viral Community Composition of Freshwater Springs in Florida, USA
3. The biomass and biodiversity of the continental subsurface;Nat. Geosci,2018
4. W. A. Overholt , S. Trumbore , X. Xu , T. L. V. Bornemann , A. J. Probst , M. Krüger , M. Herrmann , B. Thamdrup , L. A. Bristow , M. Taubert , V. F. Schwab , M. Hölzer , M. Marz , K. Küsel , Carbon fixation rates in groundwater similar to those in oligotrophic marine systems. Nat. Geosci., 1–7 (2022).
5. Thousands of microbial genomes shed light on interconnected biogeochemical processes in an aquifer system