Deep-sea chemistry
Day 6: New tools prove their worth
August 15, 2011

Location: Spinnaker Gas Vent site
Latitude: 48º 42.86 N
Longitude: 126º 54.1463 W

The changing chemical composition of the deep ocean has historically been hard to measure, but with new tools, scientists are making breakthroughs. Ocean chemist Peter Brewer has led the development of a series of instruments to tease out the ocean’s chemical secrets, and today he put one of the most effective such tools to work on both a solid and a liquid.

The laser Raman spectroscopy system, which can determine the chemical composition of a substance by the light bounced back from a special laser beam, was used on a solid structure just below the top layer of sediment, and on the water within the mud. For each test, the laser system was configured slightly differently.

We were working in an area marked by a number of pits and mounds, at a depth of about 1,300 meters. A saw-toothed tool was used to cut out a core of the solid ice-like methane hydrate. Then the Raman laser was pointed directly at the hydrate in the tube.

Clockwise, from top left: A coring tool is pushed into an outcrop of white methane hydrate, sticking out of the mud. This core had some mud at the end, but once the mud was pushed out, the ice-like hydrate remained. The laser tool is pointed at the hydrate at the end of the core. The laser is pushed deep into the sample to be sure it is covered by hydrate rather than the surrounding seawater.

The members of the science crew, gathered in the shipboard control room, were excited when the first core results appeared up on a large monitor—it showed the largest methane signal we’ve seen all week.

spectra reading
Part of the spectra reading from the laser Raman system. The very large peak at the left is of the greatest significance, showing the presence of a substantial amount of methane in the hydrate sample.

“That is a nice spectrum,” Brewer said. “Look at that peak. It’s like the Empire State Building. That was a success of the finest kind.” This was music to the ears of research technician Peter Walz who worked long and hard to make sure the entire laser Raman system would be in good working order for this cruise.

Earlier in the day, the laser system was used to measure gases in the pore water (the water within the mud on the seafloor). To reach this water, the 30-centimeter-long (one foot) probe tip was on the laser system. Using a robotic arm on the remotely operated vehicle (ROV), the pilot inserted the full length of the probe into the seafloor.

laser probe
The laser probe is inserted into the seafloor in search of methane gas.

The laser is operated remotely from aboard the ship. A little bit of water from within the mud is sucked into the probe, then passes in front of a laser beam. The light bounced back from the laser indicates what chemical compounds were in the water. Methane gas was obvious in the first hit. So was sulfate, but the best part was that as the probe was inserted further into the mud and more readings were taken from the instrument, the methane signal got stronger and the sulfate signal got weaker—exactly as Brewer expected. Also obvious in the reading was that the byproducts of the combination of these two gases were also present: sulfide and bisulfide. Chalk up another success for the day!

peter walz setting up tripod
Peter Walz sets up the tripod that will be used tomorrow to assure controlled insertion of the laser probe into seafloor mud, which sometimes is very soft and spongy.
tubeworm nest
A chandelier on the seafloor? Actually it’s a conglomeration of tanner crabs, tubeworms, and Neptunea snails sitting on their egg towers that look like corn cobs.
Benthoctopus and Neptunea snails on the seafloor.

— Nancy Barr

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Leg 1

R/V Western Flyer

The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.

ROV Doc Ricketts

ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.

Laser Raman spectrometer DORISS2

By bouncing a specially tuned laser beam off of almost any object or substance—solid, liquid, or gas—a laser Raman spectrometer can provide information about that object's chemical composition and molecular structure.

Push cores

A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.


Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.

CO2 accumulator

Carbon dioxide is a liquid at the temperatures and pressures on the seafloor where hydrates are known to occur. Because of this, one cannot simply take down a tank of gas and expect to be able to release it at depth. Instead, the CO2 piston accumulator is used to deliver precise volumes of liquid CO,2 to experiments on the seafloor. The valves are operated hydraulically by remote control and hydraulic pressure is used to expel the liquid CO2 and deliver it to the experiments.

Heat-flow probe

MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path.  The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean.


R/V Western Flyer

Ian Young


George Gunther
First Mate


Matt Noyes
Chief Engineer


Andrew McKee
Second Mate


Lance Wardle
First Engineer


Olin Jordan


Paul Tucker
Second Engineer


Vincent Nunes


Dan Chamberlain
Electronics Officer


Patrick Mitts


ROV Doc Ricketts

Knute Brekke
Chief ROV Pilot


Mark Talkovic
Senior ROV Pilot


Randy Prickett
Senior ROV Pilot


Bryan Schaefer
ROV Pilot/Technician


Eric Martin
ROV Pilot/Technician


 Research Team

Peter Brewer
Chief Scientist

Peter has taken part in more than 30 deep-sea cruises, and has served as chief scientist on major expeditions and on more than 90 ROV dives with MBARI ships and vehicles. His research interests include the ocean geochemistry of the greenhouse gases. He has devised novel techniques both for measurement and for extracting the oceanic signatures of global change. At MBARI his current interests include the geochemistry of gas hydrates, and the evolution of the oceanic fossil fuel CO2 signal. He has developed novel techniques for deep ocean laser Raman spectroscopy, and for testing the principles and impacts of deep ocean CO2 injection.

Ed Peltzer
Senior Research Specialist

Ed is an ocean chemist who has been with MBARI since 1997. He has been involved in developing in situ laser Raman spectrometry instruments and lab based analytical techniques to study the composition of gases in gas hydrates and deep-sea vents. He has collaborated on the development of new instrumentation for the measurement of temperature and pH from ROVs and deep-sea observatories. As the group's project manager, Ed is also responsible for expedition planning and logistics.

Peter Walz
Senior Research Technician

Peter has worked as a research technician for a variety of scientists at MBARI. Most recently he has supported the research efforts of Dr. Peter Brewer and his interests in the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter assists with the design, testing and deployment of the ocean going science hardware and works closely with the marine operations group to integrate new equipment to work with MBARI's ROV's.

Andreas Hofmann
Postdoctoral Fellow

Andreas is a MBARI Postdoctoral Fellow in the Brewer lab. He obtained a PhD in marine biogeochemistry in the Netherlands after his biology undergraduate and bioinformatics graduate studies in Germany. Andreas' specialty is pelagic and benthic biogeochemical modeling with a focus on pH and proton cycling. At MBARI, Andreas is working amongst others on the characterization of marine hypoxic and suboxic zones, focusing on the explicit description of physical limitations to aerobic respiration. On this cruise, Andreas will be involved in obtaining and processing Raman spectra, as well as in various other tasks supporting the objectives of the group.

Nancy Barr
Web/Print Project Manager

Nancy manages the editing, design, and production of the MBARI annual report and participates in a variety of editorial and communication projects. She also oversees the institute website. Nancy has been to sea with several MBARI research groups, helping them to carefully remove worms from whale bones, annotate video, sift seafloor sediment, and collect and process water samples. For this expedition she will be in charge of the daily reports that will be posted to this website and will assist with other science crew tasks.

Elizabeth Coward
Summer Intern

Elizabeth is an MBARI summer intern in the Brewer lab. She is a senior at Haverford College, PA, where she is obtaining her undergraduate joint degree in biology and chemistry. Elizabeth's prior research has been principally concerned with the bioavailability and geochemical dynamics of oil in marine sediments. Her interest in oceanic fossil fuels and greenhouse gases has brought her to the Brewer lab, where she will be using laser Raman spectroscopy to investigate methane and carbon dioxide signatures, the dynamics of gas hydrates and ocean acidification.

Michael Riedel
Research Scientist
Natural Resources Canada - Geological Survey of Canada

Michael Riedel was part of an international team of scientists supported by the Integrated Ocean Drilling Program (IODP) which completed a unique research expedition in 2005 aimed at recovering samples of gas hydrate, an ice-like substance hidden beneath the seafloor off Canada's western coast. As IODP Expedition 311's co-chief scientist, Michael explored his interest in gas hydrate; he believes such deposits have played an important role in ancient global climate change.

Laura Lapham
Postdoctoral Researcher
National Energy Technology Lab, U.S. Department of Energy

Laura's research is concentrated on studying methane cycling at cold seeps, biogeochemcial cycling of methane and sulfer in deep sea sediments, development of deep sea instrumentation to collect novel samples, stable isotope geochemistry, modeling of biogeochemical processes and temporal variability of dissolved methane concentrations. The focus of her research has been mainly on gas hydrate environments, but she is also interested in other systems that relate to the carbon cycle. Her research seeks to understand how methane is distributed between different pools, e.g. dissolved or hydrate phases, and also to understand how local biogeochemical processes affect this methane, mostly through anaerobic methane oxidation.

Jon Furlong
University of Victoria

Jon is a graduate student at the University of Victoria studying with Michael Riedel. His bachelor's degree was completed in Earth Sciences from Memorial University in Newfoundland before he moved from one coast to the other. Jon's research focuses on neo-tectonic faulting offshore Vancouver Island and its links to gas hydrate formation and fluid migration.