Note: We are very excited to start with a new series of dispatches from an expedition for our blog. Dr. Katrina Edwards is about to sail far into the Atlantic Ocean, drill deep into the ocean floor, and study the microbial communities found there. Today, Dr. Edwards presents an introductory overview of the journey and will post a couple of more times before she leaves in mid-September. Then, through the rest of September, October and November, she will be sending regular dispatches from the ocean floor. I hope you enjoy going for a virtual ride with her as she explores the unknown and shares with us her experiences, trials, tribulations and scientific findings.
Of all the habitable parts of this planet, one ecosystem remains nearly unexplored, and unknown to science: the igneous ocean crust. This rocky realm is poor in organic carbon substrates (i.e., carbohydrates) that usually fuel microbial life, but is rich in inorganic substrates (e.g., iron, sulfur) that come from the rock itself. This ecosystem also represents one of the largest on Earth. It has been estimated that up to 1/3 of Earth’s biomass carbon exists as microbial cells in the deep ocean sediments that overly the igneous ocean crust. While we currently do not have any cell abundance estimates for microbes in the crust, we do know that the habitable portion of the rocky ocean crust is about ten times larger than the habitable pore space for microbes in deep ocean sediments, globally. Imagine how much microbial biomass may be hidden in the porous rock! This expedition will alter the landscape of our knowledge of this rocky biome, with potential for forever changing our understanding of microbial life on Earth, our intraterestrial biosphere.
Expedition 336 takes the Integrated Ocean Drilling Program’s (IODP) flagship, the Joides Resolution, to a site known as "North Pond", located the very middle of the Atlantic ocean. North Pond (22°N, Western flank) is a famous site for Ocean Drilling; originally drilled in 1975/1976 for the purposes of examining the geology of the ocean crust, this location has been studied nearly continuously for its geological, geophysical, and hydrological characteristics since first drilled. Now, we start a new chapter for North Pond, as well as for scientific ocean drilling: microbiological research. This expedition will be the first dedicated to study of the microbiological characteristics of the igneous ocean crust – the rocky realm that lies beneath the sediments – and will establish a long-term presence at the seafloor through the creation of subseafloor laboratories. These subseafloor laboratories are called "CORKed observatories", and are used to monitor temporal changes in the geophysical, geochemical, hydrological properties of a system and now – microbiological properties.
CORK stands for circulation obviation retrofit kit. This is basically an acronym that was dreamed up to fit the term "CORK" because these devices effectively create a seal at the seafloor, enabling researchers to deploy instruments, experiments, and sampling devices down inside the cored borehole, that can communicate with the surface through specialized sensors and fluid umbilical lines. Deployments are designed for collection up to five years after deployment, and the physical structure that maintains the open hole may be used for decades to come. That technology now exists to permit active experiments to be conducted below the bottom of the ocean is really quite amazing, and relatively new to ocean drilling. Microbiological experiments that can be conducted include colonization experiments, perturbation experiments, isotopic experiments, and more. Only a few experiments have been deployed in CORKed observatories, and again, never before associated with a program that is dedicated to microbiological research.
Exp. 336 is not only intending to establish CORKed observatories, but also will collect rock and sediments from below the bottom of the ocean. From these samples, scientists are planning to analyze them for their microbiological content using genetic, genomic, proteomic, biogeochemical and cultivation techniques. From analyses on these recovered materials, as well as similar analyses to be performed on recovered experimental materials from CORKs, scientists hope to learn about the what kind of microbes reside in the ocean crust and sediments, what they might be doing, and how active they are in biogeochemically important processes such as in the transformation of iron, sulfur, and carbon. This work, focused one of largest nearly unexplored territory on Earth, will forever change our understanding of microbial populations, their function and activities and ultimately, the consequences of their existence in the oceanic crust.
About the Author: Katrina Edwards is a geomicrobiologist who studies the microbiology of hydrothermal sulfides and the igneous ocean crust. She has particular fascination with one common, yet elusive microbial group associated with these deep habitats, the iron oxidizing bacteria. These are the bacteria that make rust. She received her Ph.D. in geomicrobiology from the University of Wisconsin, Madison, in 1999 and spent the following 7 years as a researcher at the Woods Hole Oceanographic Institution, Massachusetts, USA. This is where she "sunk to the bottom of the ocean" and never came back up. She is now a Professor of Biology and Earth Sciences at the University of Southern California, Los Angeles, and is the Director of the Center for Dark Energy Biosphere Investigations (C-DEBI), an NSF sponsored program created at USC expressly for the study of the deep marine biosphere. Katrina has a husband and three children waiting at home for her during this long expedition.
Image Credits: Joides Resolution in Honolulu; author photo by Jason Sylvan.