 Leg 3 Logbook - Gas Hydrates
Day 7 — Just the same old stuff (whale bones and underwater gas eruptions)
August 8, 2009 Latitude 48 degrees 40.26 minutes N We had so much fun exploring the slope east of Bullseye Vent yesterday that we decided to try it again today. So it was like déjà vu all over again (to quote Yogi Berra), except that we found even more cool stuff! As I mentioned in Thursday’s blog, despite its name, Bullseye Vent is a long, narrow, rectangular pit in the seafloor, oriented northeast to southwest. Data from our mapping AUV suggests that the hole is elongated because it runs along a fault. Charlie’s goal today was to try and look at an underwater slope east of the Bullseye Vent where we might find evidence of this fault on the seafloor. 
As we searched the seafloor for methane vents, we
found many “gardens” of sea pens, each with its own brittle star.
At first we seemed to have no luck—all we saw were broad expanses of muddy seafloor dotted with sea pens. These relatives of corals look like half-meter-long sticks embedded in the seafloor, with lots of little purple flowers all along the length of the stick (the flowers are polyps—individual animals in a colony). At the top of each sea pen was a brittle star, its snake-like arms waving in the current, like Medusa’s hair. We don’t know for sure, but we think the brittle stars climb up the sea pens so that they can catch tiny animals and bits of debris drifting by on the currents. Anyhow, after meandering among the sea pens for an hour or so, we decided to head back to the whale skeleton that we discovered yesterday. We spent an hour or two at the whalefall today, photographing the bones, and collecting one small piece of bone to take back to Bob Vrijenhoek’s lab at MBARI. We also collected several push cores full of the black, smelly ooze from underneath the whale bones. We also looked for the cool bone-eating worms that Bob first discovered a few years ago, but didn’t see any, at least in the ROV’s video. 
Taking a closer look at the whale skull
we found yesterday, we discovered tubeworms growing up from underneath
its jawbones.
One thing we did see, however, was vestimentiferan tubeworms growing up from underneath one of the whale’s jawbones. In Monterey Bay, these tubeworms are usually found at methane seeps, but not at whalefalls. These worms can live for over 100 years, and may take decades to form a colony. From the size of the worm colony and the decay of the whale bones, it’s possible that this whale skeleton could have been lying on the seafloor for 50 years or more! Bob’s research group gives names to all of the whalefalls that they have studied in Monterey Bay. We decided to name this whalefall “Shannon” after Shannon Johnson, a research technician in Bob’s lab who works on a lot of the whalefalls in the bay. Shannon has not only led a dozen whalefall dives on the research vessel Point Lobos, but has had the unenviable task of cutting up dead whale bones with a chain saw. She's an incredibly dedicated scientist—and it's a bit of a smelly job to work with dead whales. After bidding farewell to “Shannon,” we went looking for more methane seeps and for evidence for the fault that appears to cut through the Bullseye Vent. Not far from the whalefall we found a beautiful little mound in the seafloor, perhaps three meters across. With its star-shaped cracks, it looked just like the active methane vent we found yesterday. This mound wasn’t emitting bubbles, but we thought we’d collect a vibracore to find out what was beneath the surface. I should explain that we collect vibracores in thin-walled aluminum tubes about 6 centimeters in diameter and up to two meters long. To collect a core, we mount one of these tubes on a vertical stand on the ROV. A motor containing a heavy weight is then attached to the aluminum tube. When we run the motor, the tube vibrates. This liquefies the surrounding sediment and (in theory) allows us to push the core into the seafloor. After pushing the tube in as far as possible, we pull the tube out and hope the layers of sediment will stay inside the tube until we bring it back to the surface. In any case, as we were pushing the vibracore tube into the seafloor at this one mound, a few bubbles came trickling out the side of the tube. We were excited to see evidence of methane this close to the seafloor. Then the tube stopped moving, apparently because it had hit a layer of harder sediment. Somewhat disappointed, we started to pull the core out. As we did so, more and more bubbles came out, until they formed a spectacular plume of bubbles that rose up into the water column. In taking the vibracore, we had inadvertently created our own methane vent! 
After collecting one vibracore, we inadvertently
created an underwater “geyser” of methane bubbles.
Even after we removed the vibracore, the geyser of bubbles kept growing. Seeing how pressurized the gas was, we were a little afraid it would cause damage to the ROV, or that the seafloor itself would start buckling underneath us. Charlie exclaimed, “It’s almost as if we had a blow-out on a gas well.” We could only guess that the gas had been trapped underneath a layer of hard sediment, which we had breached or weakened with our vibracore. Fortunately, the stream of bubbles peaked after 10 or 20 minutes, and then began to slow down, which allowed us to collect water samples and additional sediment cores around our newly created vent. The pilots even managed the neat trick of landing the ROV right on top of the vent, so that our heat-flow probe could be directed into the bubbling borehole. After that excitement, we flew around the area looking for other mounds covered with cracks. They were easy to see because the cracks were often filled with white mats of bacteria. We found quite a few mounds, and collected cores at several of them. Although we created one or two new methane vents in the process, none were quite as dramatic as the first one we came to. When we returned to our original site several hours later, it was still burping intermittently. It was a little hard to tell for sure, but most of the mounds seemed to lie right along the fault line Charlie had been looking for. Thus we had apparently managed to both find the fault zone and locate a collection of methane seeps of various ages. And in the process, we’d had a little adventure, as well! We also saw rocks over 10 centimeters across that looked as if they’d been lifted up out of cracks in the seafloor by recent gas eruptions. These could provide circumstantial evidence for some of Charlie’s theories on how Bullseye Vent formed. 
Chief Scientist Charlie Paull inspects an
elaborate array of syringes we used to extract fluids from the sediment
at different levels within a vibracore that we collected today at a
methane seep.
Ironically, we spent the last two or three hours of the dive searching unsuccessfully for additional mounds and seeps. At some point in the afternoon, the ship’s captain came into the control room holding an official-looking piece of paper. He informed us that he had received a fax from the NEPTUNE Canada cable-laying ship. They informed us that they were going to begin operations around the southern Bullesye Vent in about 12 hours, and requested us politely to leave the area. So tonight we’ll be heading a few kilometers north to another area called “Spinnaker Vent”. This site was apparently named after a local brand of beer. After all the excitement of the last couple of days, I can’t wait to see what’s brewing down there. —Kim Fulton-Bennett
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Track the ship
Equipment
 R/V Western FlyerThe 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 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.
R/V Zephyr is the primary support vessel for MBARI's autonomous underwater vehicle (AUV) program. This 26-meter vessel is also used to maintain environmental moorings, collect time-series data along the California Current, and support scuba divers as they study near-shore habitats.
The MBARI Mapping AUV is a torpedo-shaped vehicle equipped with four mapping sonars that operate simultaneously during a mission. The multibeam sonar produces high-resolution bathymetry (analogous to topography on land), the sidescan sonars produce imagery based on the intensity of the sound energy's reflections, and the subbottom profiler penetrates sediments on the seafloor, allowing the detection of layers within the sediments, faults, and depth to the basement rock.
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 ROV Tiburon'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.
The benthic elevator allows us to carry more than the ROV itself can carry. Loaded with sediment enrichers, it is deployed from the ship before the dive and free-falls to the bottom where the ROV pulls the equipment from the elevator for use. After the ROV is recovered, the elevator anchor's acoustic release is triggered from the ship, and the elevator freely ascends to the surface and is recovered.
Niskin bottles are used to collect water samples as well as the tiny bacteria and plankton in the water. The caps at both ends are open until the bottles are tripped, when the caps snap closed.
Held by the ROV's manipulator, the wire on the right is placed into the fluid emitted from a hydrothermal vent to record the temperature. Research Team
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.
During expeditions, Bill Ussler is primarily responsibility for the operation of the custom-built, portable chemistry lab van which contains a complete analytical laboratory for the analysis of the fluids and gases contained in marine sediments. Along with colleague Charlie Paull, Bill studies how methane (natural gas) forms and moves within seafloor sediments.
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.
Ross's research interests are in seismo-acoustic propagation, with specific application to the study of marine gas hydrates, and development and application of acoustic inverse methods for estimation of geophysical properties of the ocean bottom and for source localization. (Note: At the last minute Ross was unable to participate in the cruise, although he did attend the initial science meeting before the ship left the dock.)
As a member of the USGS Coastal and Marine Geology Program, Mary McGann's professional interests include: foraminiferal and pollen biostratigraphy, paleoecology and biogeography; sedimentary paleoenvironment mapping, quaternary paleoclimatology; and AMS C-14 chronostratigraphy.
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.
Kim helps people outside of the institute to understand MBARI's research and development efforts. He does this by writing news releases and articles about MBARI research, as well as by helping members of the press who want to write their own articles or create video stories about MBARI. His academic background is in marine geology, environmental planning, and science writing.
Yirang is an undergraduate at UC Davis in Environmental Studies and Ecological Engineering. She is an exchange student from Korea University who is interested in methane hydrates as an alternative energy source and in the ecological communities around methane seeps. She is very happy to have the opportunity to go on this cruise.
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