Marine Microbiology
For more than three billion years, microbes have served as the primary engines of Earth's biosphere, mediating essential biogeochemical cycles that shape planetary habitability. In particular, the world's oceans are teeming with microscopic life forms, and it is predicted that the oceans harbor 3.6 x 1029 microbial cells, encompassing a staggering amount of metabolic and genetic diversity. Although they are largely invisible to the naked eye, microbial communities of untold diversity continue to dominate nearly every corner of our oceans, from the deepest marine sediments to the sun-drenched coral reefs. Despite their crucial role in elemental cycling, carbon sequestration, and earth's evolution, the marine microbial world remains vastly undersampled, and our understanding of these microbial communities severely limited.

The Subseafloor Biosphere
One particular realm of the marine world that remains poorly studied is also one of the largest and least accessible, the subseafloor crustal environment. Circulation of seawater occurs within the porous upper 500 m of basaltic extrusives, and there is constant interaction and exchange between the crustal aquifer, marine sediments, and seawater. The emerging picture of the deep-sea includes the subseafloor as not necessarily an isolated environment, but instead as an important component of oceanic circulation and chemical cycling, and for that reason alone, it deserves more attention. However, it is the subseafloor microbial community living within oceanic crust that offers opportunities to study many exciting and cutting-edge aspects of marine microbial ecology, including limits of life, molecular evolution, microbial diversity and biogeography, functional genomics of complex communities, origins of life, and biofilm formation. Yet the crustal biosphere remains under-sampled, and our knowledge of what microbes are present and how they are distributed in this dynamic geochemical environment over time and space is fragmentary. My lab focuses on determining the phylogenetic and physiological diversity, distribution, and genomic content of subseafloor microbial communities in the deep-sea. Microbial data is integrated with geochemical and geophysical measurements at to develop models for subseafloor contributions to biogeochemical cycling, global carbon budgets, and marine food webs.

Schematic of oceanic crust, showing generalized porosity, heat sources, and fluid circulation patterns in the subseafloor. Image Credit: Julie Huber

Study Sites

• Axial Seamount, Juan de Fuca Ridge in the northeast Pacific (45.92° N, 130° W)
• Seamounts along the Mariana Arc (14-22° N, 143-146° E) in the western Pacific
• Loihi Seamount (18.92° N 155.27° W), the newest Hawaiian Island

My main three study sites represent geographically and geographically distinct deep-sea seamounts across the Pacific Ocean. All three locations host recently eruptive seamounts located above 2000 m with diffusely venting fluids that contain high concentrations of carbon dioxide. However, their geological and chemical setting differs greatly; Axial is a mid-ocean ridge seamount with fluids dominated by high concentrations of hydrogen sulfide, Loihi is a mid-plate hotspot seamount with extremely high concentrations of dissolved iron (FeII), and the Mariana seamounts are at a convergent plate boundary and host a variety of fluids, including those with very low pH and high concentrations of particulate sulfur. These sites were chosen for a number of reasons, including 1) access to actively venting low-temperature hydrothermal fluids and the subseafloor microbial community, 2) experience and collaborations with an interdisciplinary research team at all sites providing a wealth of geological, chemical, and biological studies to set the context for subseafloor microbiological analyses, and 3) the emerging importance of seamounts as biological hotspots in the ocean (Seamount Biogeosciences Network).

Julie and Dr. David Butterfield collecting samples from “The Beast” during an expedition to the Mariana Arc. Image Credit: NOAA Ocean Explorer

Diffuse vent Marker 52 from Axial Seamount on the Juan de Fuca Ridge taken by the ROV ROPOS. Image Credit: NOAA/PMEL Vents Program

Other Projects
Outside of deep-sea hydrothermal vents, I have research interests in a variety of different areas, all focused on marine microbiology. These include:

• Microbiology of a Sediment Pond and the Underlying Young, Cold, Hydrologically Active Ridge Flank
  Funded by the Integrated Ocean Drilling Program
• From Early Biospheric Metabolisms to the Evolution of Complex Systems
  Funded by NASA Astrobiology Institute
• International Census of Marine Microbes
  Funded by the Alfred P. Sloan Foundation
• Microbial Population Structure of the World's Oceans
  Funded by the William H. Keck Foundation
• Anthropogenic impacts and profiling fecal microbial populations at a salt marsh
  Funded by the Woods Hole Center for Oceans and Human Health

Relevant Links
New Millenium Observatory
Submarine Ring of Fire
NASA Astrobiology Institute
International Census of Marine Microbes
Woods Hole Center for Oceans and Human Health
L'Oreal USA For Women in Science
Association for Women in Science