Monterey Bay Aquarium Research Institute

Faults, Vents, and Seeps Logbook
Leg 6, Day 6: Clam dig in the deep sea
April 13, 2012

We traveled back to the northern part of the Guaymas Basin today and did two remotely operated vehicle (ROV) dives on the transform fault scarp that runs through the Gulf of California. Our first dive took us down to 1,800 meters (5,900 feet) where the ROV traversed over to the bottom of a 150-meter (490-foot) wall and ascended along this feature looking for cold seep clams and tubeworms. The wall was very steep, muddy, and had few organisms living on it. It looked like a dynamic environment—there were areas where rocks had slid down, forming scree slopes (inclines of broken rock fragments) similar to those on the sides of mountains. Along the way, we sampled tubeworms and clams for comparison to others we have sampled in the Gulf of California. We also found brachiopods, scaleworms, and a number of small limpets and snails that live amongst the clams and tubeworms.

—Kris Walz

manipulator arm with clams

The ROV pilots use this metal scoop (a retrofitted prospector's bucket) to scoop up clams from the muddy seep areas. One manipulator arm is holding the box open while the other manipulator arm pours these large cold seep clams into the sampling box.

The ROV was recovered mid-day after a very successful morning collecting biological specimens. After the samples were removed, the core tubes and sampling boxes were replaced with empty ones and the ROV was re-launched about a kilometer (0.6 miles) to the northwest. This dive was also located so that the ROV would land near the base of the same northwest-southeast oriented scarp—approximately 100 meters (320 feet) tall at this site—with the goal of again transecting up this feature. However on this dive, there were geomorphic features of interest at both the base and top of the scarp that we could identify from the recently collected autonomous underwater vehcile (AUV) surveys.

On the floor of the basin almost immediately below the main scarp, a distinctive northwest-southeast oriented lineation (linear structure) seen in the bathymetry is believed to be the trace of the transform fault. In places this lineation is manifested as a narrow trough that is around 10 meters (33 feet) deep and less than 20 meters (66 feet) wide. The ROV went directly to the bottom of the trough and took both sediment cores and thermal measurements before flying through this narrow trough for 100 meters (320 feet). The floor of this trough was generally covered with a mud drape that made it difficult to see the expression of the fault. However, the trace of the fault also was observed as a one-meter-high (3.3-feet) step further along where a relatively sharp contact was seen between firm, hard, clearly older material exposed on one side and a young sediment-draped material on the other side.

After inspecting the fault, the ROV turned and flew up the major slope. The face of the scarp was again studded with blocks of talus and scattered with clam shells. Some of the talus blocks were heavily encrusted by serpulid worms. One patch of clams was sampled.

Another objective of this dive was to ground truth the nature of a distinctive rough texture that the AUV survey shows occurring on the crest of this ridge at the end of this transect.  The ROV observations show that this rough area is associated with huge blocks of carbonate-cemented sediments.  Many of these blocks were larger than automobiles, and had open cracks or fissures that separated blocks of carbonate more than two meters deep. This type of carbonate is known to form at methane venting sites. Before we had the one-meter bathymetric grids, we would spend whole dives searching for such features. We are now increasingly confident that we can use this texture to identify the occurrence of these carbonates in the AUV data, which allows the location and extent of such methane-venting sites to be identified remotely.

—Charlie Paull

Large carbonate outcrop at the top of the fault scarp wall.

During this cruise we are also hunting for a particular scaleworm named Bathykurila guaymasensis. They are tiny worms, measuring up to one centimeter (0.4 inches), and bacterial mats are their favorite food. The species was originally described from vents here in the Guaymas Basin in 1989 by Marian Pettibone, but no molecular information was collected back then. Later these worms were found on whale falls in Southern California. Recent molecular data from the specimens from Southern California points to two different species. Now the question we want to solve is: which of the two species is the real Bathykurila guaymasensis? We already found a few individuals, but we are still looking for more so we can compare different populations from here to those in Southern California.

—Sigrid Katz

This tiny, one-centimeter-long (0.4-inch) scaleworm, Bathykurila guaymasensis, was originally described from the Guaymas Basin and feeds on bacterial mats. Photo by Greg Rouse.
ROV Pilot Randy Prickett watches as the ROV Doc Ricketts is recovered from today's dive. There are two cranes in the moon pool: one for handling the tether management system during the dive (back crane operated by Dan Chamberlain) and another for launch and recovery of the vehicle (front crane operated by George Gunther). Jason Jordan and Matt Noyes are recovering the tether behind the vehicle.
ROV Doc Ricketts
We were rewarded with beautiful weather during the sunset this evening.  Everyone came out on deck to see if they could catch a glimpse of the green flash (no luck!). Sigrid Katz, Krystle Anderson, Josh Plant, and Charlie Paull on deck.
Sunset from the R/V Western Flyer
Another beautiful sunset off Baja California.


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 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.

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.

In situ gas sampler

These are devices that are used to collect and sample gaseous gases bubbling out of seafloor vents. The way they work is by having small pressure vials (like tiny scuba tanks) from which the air is pumped out with a vacuum pump on the surface and sealed with the valve. On the bottom gases are captured underneath an overturned funnel so that a large gas headspace is developed. Then the value on the pressure vial is opened, gas is sucked into the vial, and the vial's value is re-closed. This way a sample of the gas at the high seafloor pressures is recovered.

In situ ultraviolet spectrophotometer (ISUS)

The ISUS is a sensor used to measure concentrations of dissolved chemicals directly from their Ultraviolet Absorption Spectrum. A variety of chemicals absorb light in the UV and each of these chemicals has a unique absorption spectrum. We can determine the concentration of these chemicals directly, with no chemical manipulation, by measuring the absorption spectrum of seawater in the UV and then deconvolving the spectra to yield the concentration of each component. ISUS has been used to determine nitrate concentrations while deployed on CTD/Rosette profilers, undulating towed vehicles such as a SeaSoar or SeaSciences Acrobat, and on deep-sea moorings. It has also been used to measure sulfide flux from cold seeps in Monterey Bay while deployed on the ROV Ventana.

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.

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.

Gravity corer

Device lowered off the ship to the seafloor on a wire which consists of a long tube that extends below a moderately heavy weight. When the device encounters the bottom, the weight forces the tube into the sediments. When it is pulled out of the bottom the tube will contain a sediment sample (i.e., core) of the upper layers of the ocean floor.


 Crew

R/V Western Flyer

Ian Young
Master


 

George Gunther
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


 

Eric Fitzgerald
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


 

 Leg 6 Research Team

Charlie Paull
Chief Scientist
MBARI

Charlie Paull has been a marine geologist and geochemical stratigrapher at MBARI since January 1999. The central theme of Charlie's work involves investigating the fluxes of fluids and gases through continental margins. Over the past decade his primary focus has been gas hydrate research on the Blake Ridge gas hydrate field on the continental rise off of southeastern North America. Assessing the global distribution of gas hydrate and interstitial gas is a continuing interest as well as the development of new techniques to detect the presence of gas hydrate in marine sediments. Charlie's other ongoing work is focused on the geology associated with seafloor seepage sites, including investigating the deposits associated with chemosynthetic communities, determining the processes that occur at the methane-sulfate boundary, and understanding the origin of pockmarks and other potential seafloor fluid venting sites.

Bob Vrijenhoek
Chief Scientist
MBARI

Bob Vrijenhoek leads MBARI's molecular ecology group, which focuses on using molecular tools to examine population structure and evolutionary relationships. His group is working on a number of projects studying gene flow and barriers to dispersal of deep-sea invertebrates associated with cold seeps in the Monterey Bay and hydrothermal vents at ridge sites throughout the world. The group also studies DNA sequence information from bacterial symbionts to examine their evolutionary relationships with their hosts and infer possible modes of transmission.

Krystle Anderson
Research Technician
MBARI

Krystle Anderson is a research technician working for Charlie Paull in the Continental Margins Lab. Krystle's background is primarily in the acquisition and processing of seafloor mapping data. She came from the California State University, Monterey Bay Seafloor Mapping Lab where she obtained her data processing and Geographic Information System (GIS) skills. Krystle spends a majority of her time processing and creating high-resolution maps of multibeam data collected from the mapping AUV. The high-resolution maps Krystle helps create will then be used to aid navigation for the ROV to explore particular areas of interest. On this expedition Krystle will assist with running the GIS system, and processing and cataloguing sediment samples and vibracores. This is Krystle's second research expedition with MBARI and she is very excited to be involved in this expedition.

Roberto Gwiazda
Research Specialist
MBARI

Roberto is a geochemist by training. His interests lie at the intersection of marine geology and sediment and water chemistry. During cruises Roberto operates a custom-built, portable chemistry lab that includes a complete set of analytical platforms for measurements of fluids and gases. On this expedition, Roberto will be responsible for analytical measurements of pore water chemistry on samples taken from sediment cores. He will also be in charge of collecting gas samples emanating from fluid vents and performing hydrocarbon analyses on dissolved gases collected from pore waters, from gas vents and from seawater.

Josh Plant
Research Technician
MBARI

As a member of Ken Johnson's Chemical Sensor team, Josh spends much of his time analyzing chemical data collected from instruments developed by the group. One of the main goals of these measurements is to decipher how biology affects the cycling of the measured chemicals. In the Gulf of California Josh will be measuring the distribution of sulfide in waters overlying cold seep communities as well as helping to process biological samples for the molecular ecology group. Sulfide is one of the energy sources which fuels seep ecosystems. When not at work Josh spends much of his time on or near the ocean, fishing and hiking, or working in his garden.

Kris Walz
Research Assistant
MBARI

Kris Walz works with the Midwater Ecology team at MBARI where she studies pelagic animals and their distributions using horizontal video transects collected from midwater time-series dives (1993 to present) in Monterey Bay. She joins the science teams on this leg of the Gulf of California expedition to assist with their research by recording and annotating video during the ROV dives, and processing biological samples collected from the ROV.

Brian Edwards
U.S. Geological Survey
Pacific Coastal and Marine Science Center

Brian specializes in sedimentary processes and stratigraphy, integrating insights gleaned from seafloor rock and sediment samples with information from remote-mapping products, such as close-up photographs of the seafloor, high-resolution bathymetric maps, and seismic-reflection profiles. His recent studies have focused on how sediment moves from the land to the deep sea, processes controlling submarine landslides, saltwater intrusion into coastal aquifer systems, marine pollution, seafloor habitats, and the Cenozoic history of the Arctic Ocean.

Juan Carlos Herguera
Collaborator
CICESE

Juan Carlos is interested in the history of past oceans, how changes in climate and ocean circulation contribute to the ecology and biogeochemical cycling sustained by coastal environments in the California Current and the Gulf of California regions. During this cruise he will be involved in sampling benthic foraminifera to help characterize their genomic information, and, through their stable isotopic and metal compositions, to understand how these geochemical markers reflect their ambient conditions. He will further use planktonic foraminifera for dating the deep-sea cores with radiocarbon techniques, which hold important clues on the tectonic rupturing rhythm along the boundary between the North American and Pacific plates. He is fascinated by these new observation windows opened up by the ROV deployed from the Western Flyer, making possible the discovery of new vent environments along these fractured boundaries and the chemosynthetic oasis sustained by these leaky enclaves that connect the deep ocean with the lower crust and mantle dynamics.

Mary McGann
Research Geologist (Micropaleontology/Biology)
U.S. Geological Survey
Pacific Coastal and Marine Science Center

Mary's interests focus on using microbiota (primarily foraminifera but also pollen) to investigate marine sediment transport, geohazards (faulting, landslides and paleotsunamis), climate change, and the pathways and impact of invasive species introductions using sediment records and molecular analysis techniques. She also uses foraminifera in biomonitoring marine pollution sites and carbon-14 chronostratigraphy—the study of the age of rock layers in relation to time.

Greg Rouse
Professor
Scripps Institution of Oceanography

Greg uses morphological and molecular data to assess relationships among animals. His morphological studies range across various adult and larval anatomies using transmission and scanning electron microscopy as well as confocal laser scanning microscopy. This is combined with molecular (DNA sequence) data to infer phylogenetic relationships and hence evolutionary patterns. His research interests include the biodiversity and distribution of hydrothermal vent animals from the eastern and western Pacific, as well as those from methane seeps in the eastern Pacific. This often involves the discovery and naming of new species of animals.

Sigrid Katz
Postdoctoral Fellow
Scripps Institution of Oceanography

Sigrid is a postdoc at Scripps in Greg Rouse's lab. Sigrid received her Ph.D. in Austria working on Osedax from whale falls and has continued this work during her postdoc. She is interested in symbioses, vent organisms, and their relationships.



Last updated: Apr. 17, 2012