Deep Biosphere Laboratory

Roughly 70% of the Earth’s surface is covered by marine sediments and oceanic crust. Microbes - bacteria, archaea, tiny eukaryotes, and viruses - are major players in these environments, cycling elements and eating carbon. The marine subsurface is a vast reservoir of life on Earth, yet we don’t fully understand how all of the microbes get their energy to grow, or the full impact of their activity on chemical cycling. Actually, we don’t even have a great understanding of the full variety of environments at the bottom of the ocean! New habitats - like hydrothermal vents and brine pools - are continually being discovered. Humans have probably only seen about 1% of the seafloor - there is a lot of exploring left to do! Below is a sampling of some of the research and exploration that I am involved in.

Life on the Rocks

A large portion of the seafloor consists of rocky habitats - such as basalts and hydrothermal sulfide deposits. When in contact with oxygen-rich seawater, these rocky substrates could provide a habitat for microbial communities to thrive. I am interested in understanding which microbes can live on basalts and sulfides at the seafloor, and identifying which geochemical processes are occurring on the rock surfaces. So far, we have learned that seafloor basalts host some of the most diverse microbial communities on Earth. Drilling deeper into the oceanic crust, now we are trying to understand microbial life in deep rocks. This requires the use of sophisticated observatories installed into the seafloor - see the Observatories section below for more details. I am currently conducting research at several field sites to understand microbe-mineral interactions: the Juan de Fuca Ridge flank, the "North Pond" site on the western flank of the Mid-Atlantic Ridge, the Dorado Outcrop on the Costa Rica Rift flank, and soon at the Atlantis Massif.

Mud and Methane

A coating of sediment (‘mud’) blankets some of the oceanic crust at the seafloor, and this muddy environment is also home to microbes. Depending on location, one thousand to one trillion microbes can be found in a cubic centimeter of sediment. Since the vast majority of these microbes have so far been resistant to cultivation, we have to use some clever combinations of geochemical analysis and molecular biology techniques to figure out who the microbes are and what they are doing. Methane is generated in deep layers due to the microbial breakdown of buried organic matter. Other microbes consume a large fraction of this methane, which keeps this important greenhouse gas from escaping from the seabed. However, the microbes involved in this process seem to survive at low energy yields, and the biochemical mechanism for methane consumption with sulfate is still not well understood. My research revealed that non-methane hydrocarbons can fuel high rates of sulfate reduction in the Gulf of Mexico, that the microbes thought to be involved in methane consumption could also be involved in methane production, and that methane gas hydrates may support active microbial communities. I am currently working with several other scientists to study the impact of the Deepwater Horizon oil spill on sediment microbiology in the Gulf of Mexico. You can learn more about the ECO-GIG project supported by the Gulf of Mexico Research Initiative here.

Recently, my collaborators and I were funded to bring some of the same technology we use to study methane cycling in the deep sea to study methane build-up and release from Arctic lakes. Read more about that project here.

Deep-sea Observatories

Oftentimes, marine research involves collection of samples at one time and place - essentially a ‘snap shot’ of conditions. What happens during the rest of the year? Similarly, some environments are very challenging to access or to recover high quality samples from - such as deep oceanic crust. How can scientists study these hard to reach environments? One answer to these questions is through the use of observatories, which are essentially long-term experiments deployed in the environment (‘in situ’) that monitor the environment and/or collect samples over time. I’ve been working with colleagues to develop, install and service microbial observatories deployed in subsurface ocean crust. These observatories projects require years of investigation to monitor conditions in the subsurface and to gain a better understanding of how fluids and microbes circulate in oceanic crust.

Deep Biosphere Laboratory Group

Students

  • Francisco Spaulding-Astudillo (University of Chicago), 2015 Summer REU
  • Aurélien Lecoeuvre (University of Brest, France), visiting Master's student Jan-Jun 2015
  • Brianna Adams (Texas A&M University, Corpus Christi), 2014 Summer REU
  • Allison Sharrar (University of Michigan), 2014 Summer REU - Now a graduate student at UC Berkeley (Jill Banfield lab)!
  • Sonia Vargas (Colby College), 2014 Summer REU

Personal Website

www.microbesareawesome.com