THE CENSUS OF DEEP LIFE: A NEW PROJECT TO EXPLORE LIFE UNDERGROUND

The Deep Carbon Observatory (DCO) seeks to understand the sources, sinks, and nature of different carbon species in deep geologically diverse continental and marine environments. Part of the DCO will investigate the role of microbes in the cycling of carbon and the DCO’s Census of Deep Life (CoDL) is a new program that will characterize the diversity of life in subsurface environments using deep DNA sequencing technology. The initial goal of the CoDL is to develop population profiles of microbial communities from the continental and marine deep subsurface by soliciting samples for deep DNA sequencing analyses from investigators who study life in various earth settings. The first CoDL projects to be supported are split between seafloor and continental locations and will include surveys of the microbial diversity in cratons, basalts, serpentinized formations, methane hydrate-rich sediments, subglacial and sub ice shelf locations, mud volcanoes, and seamounts. One CoDL site where deep earth carbon defines the geology is in methane hydrate-rich marine sediments near the Andaman Islands. Low levels of total microbes, a predominance of Bacteria, and distinct communities associated with the hydrates were discovered here. Another CoDL site, from the Columbia River Basalt Group where a pilot scale injection of carbon dioxide is planned, also appears to contain Bacteria as the dominant population and with distinctly different communities associated with unique basalt flows. Initial CoDL estimates of diversity and community composition will identify sites suitable for future investigation of biological contributions to the carbon cycle using molecular microbial ecology. These same sites will provide opportunities to investigate contextual parameters that correlate with the occurrence of specific taxa. We expect that the project will conclude with an improved understanding of the importance of microbes in studies of deep life and their potential contribution to deep carbon cycling.