Affiliation: Texas A & M University

Title: Those rocks are alive! – Geomicrobiology of the deep biosphere in subseafloor igneous basement

Abstract: One of the great surprises in ecology during the last 20 years was the discovery of a vast microbial biome deep below the seafloor.  This environment, known as the deep biosphere, is the largest microbial habitat on the Earth.  We now know that as many prokaryotic cells live in subseafloor sediment as in the entire oceanic water column. Microbial biomass in the basement rocks underlying sediments is currently unknown, but can only add to that total.  Therefore, there are likely more cells below the seafloor than in the water column, making the study of the marine deep biosphere critical to understanding marine microbiology, chemistry and geology.  My research focuses on geomicrobiology in basement rocks – how many microbes are present, who they are, and what they are doing.  I will present findings from two recent IODP expeditions on which I sailed – Expedition 330, which sampled 55-80 million year old extinct volcanoes along the Louisville Seamount Chain in the southwest Pacific Ocean, and Expedition 360, which completed in January 2016 and drilled 789 meters below seafloor into 11 million year old lower crustal rocks as the first part of a multi-expedition program to drill to the Earth’s mantle.  Results from these cruises help redefine our understanding of biomass in igneous basement and provide insight into the types of lifestyles subseafloor microbes lead in these environments.