Texas A&M University
2016-2017 Distinguished Lecturer
Those Rocks Are Alive! – Geomicrobiology Of The Deep Biosphere In Subseafloor Igneous Basement

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.

Dr. Sylvan’s research focus is the microbial ecology of marine hydrothermal ecosystems and subseafloor igneous crust. He has sailed on several scientific ocean drilling expeditions, most recently IODP Expedition 360, which drilled into the Atlantis Bank on the Southwest Indian Ridge.


01 November 2016 Texas A&M University-Corpus Christi, Cospus Christi, TX
09 November 2016 Woods Hole Oceanographic Institute, Woods Hole, MA
10 November 2016 Bigelow Laboratory for Ocean Sciences, Booth Bay Harbor, ME
16 November 2016 Western Washington University, Bellingham, WA
18 November 2016 University of Alaska Fairbanks, Fairbanks, AK
23 February 2017 University of Wisconsin-Milwaukee, Milwaukee, WS
22 March 2017 Bowling Green State University, Bowling Green, OH
04 April 2017 Montclair State University, Montclair, NJ
05 April 2017 University of Maryland Eastern Shore, Princess Anne, MD
06 April 2017 University of Delaware, Lewes, DE