Award: OCE-0939564

C-DEBI's mission was to greatly expand our fundamental knowledge of the deep subsurface biosphere on Earth, with a particular focus on the igneous ocean crust and the overlying sediments. Our approach combined research efforts with the training of early career scholars, a range of knowledge transfer activities, and programs that integrated outreach and diversity. C-DEBI research in the initial phase primarily focused on exploration and discovery of subseafloor ecosystems anchored firmly in three major field programs: Juan de Fuca Ridge Flank, South Pacific Gyre, and North Pond. These field sites globally span a range of subseafloor environments, e.g., seafloor below oligotrophic ocean gyres, ridge systems and ridge flanks, and seamounts where fluids flow into or discharge from the subseafloor, with characteristics along the continuum of field habitats in sediment cover, rock type, crustal age, and fluid temperatures, among other environmental conditions that impact the deep biosphere. The overall goal was to investigate microbial life, geochemistry, and hydrology in the sediment and igneous crust of the subseafloor, beginning with a small set of focused study sites. These studies relied on a variety of truly innovative methods and tools, using numerous oceanographic technologies, including ships, submersibles, drilling, and observatories, capitalizing on the unprecedented scheduling of three ocean drilling expeditions within 18 months of each other, all with subseafloor microbiology as a major focus. As we moved forward into the second phase of C-DEBI, our exploratory and discovery-based science from multiple compelling seafloor settings was balanced with ongoing and new elements of hypothesis testing, data integration, laboratory experimentation, and modeling to develop an integrated understanding of subseafloor microbial habitats, communities, and adaptations maintaining highly multidisciplinary and interdisciplinary approaches. We had our greatest emphasis on microbial ecology, with three overarching research themes and associated research objectives: Theme 1: Fluxes, Connectivity, and Energy-centering on subseafloor environmental conditions; Theme 2: Activities, Communities, and Ecosystems-emphasizing resident microbial communities; and Theme 3: Metabolism, Survival, and Adaptation-concentrating on the actions and traits of individual microbial species. C-DEBI facilitated and encouraged the synthesis and broad understanding of submarine microbiological processes within geochemical, geophysical, and hydrogeologic contexts. This was largely accomplished by funding scientific and technical activities, coordinating and hosting meetings and workshops, and supporting researchers and graduate students (in over 100 grant projects at nearly 50 institutions including graduate student and postdoctoral research fellowships). These research endeavors generated a vast array of diverse data types and products that were managed, integrated and archived for the long term, as well as a vast array of important scientific discoveries and technical advances that were disseminated to the scientific community and the broader population through journal publications (over 500 community contributions), worldwide access to data and new technologies, exchanges of personnel, lectures and presentations, professional development activities, conferences and workshops, and targeted courses for students and educators. C-DEBI incorporated deep biosphere research into all facets of its education, outreach, and professional development programs, with a keen focus on targeting and engaging underrepresented students at all levels. We have trained and mentored hundreds of undergraduate and K-12 students, instilling enthusiasm for scientific discovery in future subseafloor research and fostering the next generation of deep subseafloor biosphere researchers. C-DEBI has nurtured a growing multidisciplinary scientific community, and coordinated a broad range of complementary activities in research and training, thereby establishing a vibrant international community of scientists in a field that barely existed before C-DEBI. In C-DEBI's short decade of existence, we have trained, mentored, and financially supported >50 graduate students and postdoctoral fellows. Through C-DEBI, almost 100 graduate students and postdoctoral scholars, dominated by women (63%) and many underrepresented minorities (20%), have transitioned (or are in the process of transitioning) to permanent career appointments with opportunities for leadership in their chosen professions. Those women and underrepresented minorities include a Nature journal editor, a number of research scientists, and 50 faculty members at universities in the USA and elsewhere. Our legacy has spawned from our scientific community of subseafloor biosphere researchers into new related programs (e.g., NASA Astrobiology Institute: Life Underground, International Center for Deep Life Investigation, Accel-Net: Crustal Ocean Biosphere Research Accelerator, International Earth 4D program through the Canadian Institute for Advanced Research). Last Modified: 03/06/2023 Submitted by: Jan P Amend