Deep-sea chemistry
Day 5: A good day for the Canadians August 14, 2011
Location: Off the coast of Vancouver Since we are spending most of this week in Canadian waters, it was a pleasure today to help our Canadian colleagues both onboard and onshore. When the Western Flyer works in foreign waters, we always invite along at least one scientist from the host nation, not only because it is a permit requirement, but also because the local scientist has much to offer in terms of his or her expertise in the area. This also gives the local scientist access to our remotely operated vehicle, which is not an easy resource to come by. Geophysicist Michael Riedel, of the Geological Survey of Canada, is serving as an observer on behalf of the Canadian government on this leg of MBARI’s expedition, and is also conducting his own research into gas hydrates. Today he collected sonar images of a wide swath of the seafloor looking for plumes of bubbles that would indicate gas vents. He was well-rewarded for the effort, finding numerous such plumes near a site called “Bubbly Gulch”. Riedel then directed the pilots to fly the remotely operated vehicle over the area he had just discovered to get a visual survey. What he saw was a large field of bacterial mats—a sign of the presence of methane gas venting—and gas percolating up from the ocean bottom at a depth of about 1,200 meters. 
This large field of bacterial mat, about 250 meters long and five-to-ten meters wide, closely followed a crack in the seafloor.
It also turned out to be a good day for a group of Canadians onshore who were looking for help out at sea. Managers at the NEPTUNE Canada program, which runs a very large cabled observatory on the seafloor in this area, were concerned about a short in an instrument on the ocean bottom. When they found out we’d be in the area, they asked us to fly by and unplug it. Not a very difficult task for our crew, which has experience working on MBARI’s own cabled observatory, so we gladly helped them out. But it was an enormous help to the NEPTUNE folks, who would otherwise have to get a ship and ROV out here to take care of it. They will still need to come out to make long-term repairs, but at least there is no immediate need, and an important seismometer is back in service thanks to the work of our pilots Knute Brekke and Randy Prickett. 
The instrument platform for the NEPTUNE Canada seafloor observatory seismometer. In the foreground is the robotic arm from the remotely operated vehicle Doc Ricketts, which disconnected an instrument at the request of the Canadians. Look closely and you may notice a hockey puck or two used on the platform. 
Tiburonia granrojo, a jelly that can grow to as much as three meters across, was spotted on today’s dive, so we followed it briefly to get some good video footage. The animal was first described by MBARI scientist George Matsumoto.
A parting shot for the day, just before bringing the ROV up to the surface, we encountered this seafloor still life. Well, probably not so still, since these animals are alive. The sea life in this picture includes a juvenile tanner crab (Chionoecetes), corals (sea fans) in the family Primnoidae, a brittle star perched on one of the sea fans, and a Neptunea snail sitting on an egg mass.
Michael Riedel, Peter Brewer, and Ed Peltzer consider the best place to dive tomorrow.
— Nancy Barr
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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.
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.
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.
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.
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
ROV Doc Ricketts
Research Team
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 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 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 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 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 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 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'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 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. |
