Abstract

A large fraction of the total global prokaryotic biomass lives in the groundwater-saturated zones of the continental subsurface. Groundwater environments are dark, and typically contain low levels of organic matter and nutrients. While these environments are locally often relatively stable over time, there can be large hydrological and physicochemical variation across space. Microorganisms catalyze essential biogeochemical processes in groundwater environments, like the cycling of carbon, nitrogen, and other elements, as well as the natural attenuation of contaminants. Instead of operating in isolation, different functional groups of microorganisms interact to drive these processes. In this chapter, we will discuss how microbial diversity and community composition is shaped by the characteristic features of groundwater environments, the importance of microbial interactions in sustaining community diversity and key biogeochemical cycles, including the attenuation of contaminants (i.e., aromatic hydrocarbons, chlorinated organic compounds, toxic metals, and organic micropollutants), and their responses to environmental perturbations.

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