The Breathing Seafloor

In the cold, dark depths of the seafloor across the world, microbes living in sediments and on rocks are quietly breaking down organic material and sucking dissolved oxygen out of the seawater. The continental shelf off of Oregon’s coasts, home to a fishing industry that brings in over a hundred million dollars of revenue per year, is no exception. Does oxygen consumption, and therefore carbon cycling, vary by location, or across seasons? Setting a baseline to investigate these patterns of oxygen drawdown is crucial to understanding habitats and distributions of fish stocks, but will also establish what “normal” oxygen consumption looks like off our shores. Measurements like these are also used by the Intergovernmental Panel on Climate Change (IPCC) to estimate global patterns of carbon burial. If any forces were to shift these patterns in the future, we’d at least have a baseline to allow us to diagnose any “abnormal” conditions.

Peter Chace is a third-year PhD student of Ocean Ecology and Biogeochemistry in the College of Earth, Ocean, and Atmospheric Sciences (CEOAS). Peter’s research focuses on developing a technique of measuring fluxes of oxygen across the seafloor called Eddy covariance. This technique takes high-resolution time measurements of three-dimensional velocities of water moving in turbulent whorls, or random circular patterns, within the boundary layer of a fluid like air or water. Eddy covariance has been employed to measure fluxes across air layers on land for decades, but has only recently been applied in marine systems. A point-source oxygen measurement within this turbulent layer is measured with a microelectrode and combined with the velocity data to develop a flux. Why go through all this trouble? Other ways to measure oxygen fluxes, like putting chambers over an area of seafloor and waiting to measure an oxygen drawdown, require a lot of work and give little temporal resolution.

Workers on the RV Oceanus, Oregon State’s largest research vessel, deploy a benthic (seafloor) oxygen sensor.

Peter can calibrate his microelectrodes to measure other chemicals and obtain their fluxes across the seabed, but he is mainly focused on oxygen. To measure fluxes off the Oregon coast, Pete and his advisor, Dr. Clare Reimers, will head to sea on the RV Oceanus several times this fall and winter to deploy their sensor on the seafloor for days at a time. The desk-sized seafloor lander and the microelectrode attached to it are fragile, and the rough seas offshore Oregon in fall and winter will make it a challenging endeavor. We hope they pack enough seasickness medication and barf bags!

You get right up close and personal with the ocean when you send down these instruments… and this is on a clear day with calm seas!

Since growing up as a child in New Jersey, Peter has always wanted to learn about the ocean. While studying chemistry and marine biology at Monmouth University (in New Jersey) as an undergraduate, he completed a summer REU (Research Experience as an Undergraduate) with his current advisor, Clare Reimers, here at Oregon State University. He also interned for NOAA (the National Oceanic and Atmospheric Association), analyzing the chemistry of hydrothermal vent fluids with Dr. David Butterfield. Pete revisited a hydrothermal system on a cruise to the East Pacific Rise off of Central America where he got a remarkable opportunity to dive in Alvin, the submersible that discovered the wreckage of the Titanic.

Here’s Pete in the submersible Alvin just before the dive, checking his microelectrodes.

To hear more about Peter’s research on sensor development and his seafaring expeditions, tune in to Inspiration Dissemination on Sunday, October 15th at 7pm on 88.7 KBVR Corvallis. Or stream it online here!

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