Monterey Bay Aquarium Research Institute

Deep-Sea Chemistry Logbook
Day 8: Sometimes you come up dry

March 21, 2012

After two dives in two different locations yesterday, today was our last chance to search for unusual chemical signals indicative of fluids being forced through the seafloor in the Gulf of California. This past week we had already worked at the gas venting sites that our scientists found during their 2003 expedition here, and located new sites atop volcanic mounds and along fault lines. However, just poking around randomly in the seafloor was likely to be a waste of time. So we dove the vehicle to explore the sites that our MBARI colleagues on the mapping team working concurrently here in Mexico had identified as targets.

Despite heavy winds and a rocking ship, we were able to get the remotely operated vehicle (ROV) in the water early this morning for a dive on a transform fault at the base of a big slump. For this spot, we had one of the new high-resolution maps produced with data from the D. Allan B. autonomous underwater vehicle (AUV) last week. The base of the slump was 2,240 meters (7,350 feet) deep. From there, it climbed 50 meters (164 feet) up a steep slope. At the top, the ROV flew along the ridge, and we stopped to take a couple of Raman profiles to determine if there was geochemical activity below the surface of the seafloor. The results were disappointing as there was just seawater within the sediment, and no gases of interest. The massive slump field far above had smothered the site with fine clay. The area was so dull that to make the most of our day, the ROV was recovered so we could steam to one last site just 22 kilometers (13.7 miles) away.

image of two monitors
The two key monitors to watch in the control room while running the laser Raman spectrometer. The lower monitor shows the probe on the seafloor in its stabilizing tripod. The upper monitor shows the spectra returned from the laser system; each peak indicates a different chemical signal.

Early in the afternoon the vehicle was back in the water at the next site. It was also along the transform fault, although in this location we were operating off older, low-resolution maps which only gave a general sense of the area. This site had even less to offer the eager crowd watching the video monitors. Just mud as far as the ROV could see. Boring, dull, and a definite letdown. But we were there and may never be there again, so we stopped again and took some pore water profiles. These profiles, combined with the video images of this never-seen-before seafloor and the new maps will help paint a clearer picture of what lies beneath the Gulf of California waters. And where fluids are pushed up, and where they are not.

The ship has now begun steaming toward port, where this science group will pack up and depart, making way for geologist Charlie Paull and his group who will be briefed on all the findings.

Ed Peltzer
During ROV dives, Ed Peltzer, left, manages the video annotation system and dive-related data and maps, and meticulously logs every detail of the dive. Peter Walz, right, manages the laser Raman spectroscopy system.
Nancy Barr
Your scribe, Nancy Barr, preparing the day’s cruise log in the ship’s lab.
Some of the day’s sights included this pink anemone (left), a long-nose ratfish (left), and a skate (below).

—Nancy Barr and Peter Brewer

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Deep-Sea Chemistry
 Equipment

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.

CTD Rosette

The CTD measures conductivity (which helps determine salinity), temperature, and density (which helps determine depth). This particular CTD runs profiles of the water column (surface to bottom) and along the way, collects discrete water samples (at specific predetermined depths) using the rosette of niskin bottles. Each bottle can collect a water sample. The transmissometer measures the number of particles in the water and the oxygen sensors tell us how much dissolved oxygen is present. Both of these instruments go onto the CTD rosette and give us a profile of the water column.

Vibracores

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.

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.

 Crew

R/V Western Flyer

Ian Young
Master


 

Andrew McKee
First Mate


 

Matt Noyes
Chief Engineer


 

Cole Davis
Second Mate


 

Lance Wardle
First Engineer


 

Shaun Summer
Relief First Engineer


 

Olin Jordan
Oiler


 

Craig Heihn
Relief Deckhand


 

Jason Jordan
Relief Deckhand


 

Dan Chamberlain
Electronics Officer


 

Patrick Mitts
Steward


 

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
MBARI

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
MBARI

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.

Nancy Barr
Web/Print Project Manager
MBARI

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. 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.

Peter Walz
Senior Research Technician
MBARI

Peter has worked as a research technician for several scientists at MBARI. For the past 10 years he has supported the research efforts of Peter Brewer and his interests regarding the ocean chemistry of greenhouse gases such as methane and carbon dioxide. Peter is responsible for the design, testing, maintenance, and deployment of the oceangoing science hardware and works closely with the marine operations group to integrate new equipment and technology with MBARI's ROVs.

Martín Hernández Ayón
Collaborator
Universidad Autónoma de Baja California

Martín Hernández Ayón is a chemical oceanographer. His research is focused on the inorganic carbon system, ocean acidification and biogeochemistry in the coastal regions of Baja California, the Sea of Cortez, the subtropical region where the oxygen minimum zone is located, and, more recently, the Gulf of Mexico.

Gabriela Y. Cervantes
Graduate Student
Universidad Autónoma de Baja California

Gaby is a graduate student in the coastal oceanography program at the University of Baja California in Ensenada, Mexico. She is doing her graduate studies on the dynamics of CO2 in seawater from a coastal monitoring site known as Ensenada Station.

Abbey Chrystal
Graduate Student
University of California, Santa Cruz

Abbey Chrystal is a graduate student in earth and planetary sciences at the University of California, Santa Cruz. Her research focuses on reconstructing long-term records of past ocean carbonate chemistry parameters. On this cruise she will be collecting sediment push cores and bottom water samples to help calibrate the relationship between the shell chemistry of benthic foraminifera and the chemistry of the bottom water and porewater chemistry in which they grow.

Joseph Murray
Graduate Student
University of California, Santa Cruz

Joseph Murray is a first year ocean sciences Ph.D. student in the lab of Dr. Adina Paytan at the University of California, Santa Cruz. He is interested in coastal marine chemistry and the impact of submarine groundwater discharge on marine biogeochemical cycles. His current research is focused on using oxygen and nitrogen isotopes in nitrate to study sources and cycling of nitrogen in the coastal ocean. As part of this cruise, he plans to collect samples in order to study the impact of anthropogenic fertilizer runoff from the Yaqui Valley on the marine nitrogen cycle in the Gulf of California, including assessing the role groundwater discharge plays in this process.



Last updated: Mar. 26, 2012