During this first leg of the Southern California Expedition, we will be
conducting a series of remotely operated vehicle (ROV) dives on sites previously surveyed by MBARI's
mapping autonomous underwater vehicle (AUV) in March of this year. These sites within the Santa Monica
Basin and south within the California borderland towards San Diego were
selected because of the similarity of their gross topography to other
sites where methane mounds and active venting of methane gas and methane
rich fluids have been found. Our plan is to visit targets of interest
where the high-resolution maps have suggested we will find more active
We will be conducting laser Raman studies of pore-water
chemistry in the sediments around the active methane gas venting sites and
seafloor mounds. Our laser Raman spectrometer bounces a laser beam off of
the target of interest—be it a solid, liquid, or gas—providing
information about that object's chemical composition and molecular
structure. The laser Raman spectrometer has recently been modified to look
at pore-water fluids withdrawn the upper 0.5 meters of sediment. This is a much
better method for studying the chemistry of the pore-water fluids in the
sediments than collecting a push core, which requires bringing the
sediments to the surface, squeezing out the pore-water and then analyzing
the chemistry. By processing the samples on-site in real-time we avoid
alterations to the pore fluids due to changes in temperature and pressure
or contamination of the reducing fluids with oxygen while processing the
samples on deck or in the lab.
Also on this leg, Victoria Orphan and her team (postdoctoral fellow Kat Dawson and graduate student Alexis Pasulka) are collaborating with Peter Brewer and Ed Peltzer to characterize active sulfur and methane cycling microorganisms and their isotopic biosignatures within methane seeps along the Southern California Borderland. During the cruise they will collect samples for stable isotope labeling experiments and microbial community characterization in parallel with the laser Raman geochemical analyses and test new ROV-deployable methods for in situ high resolution capture of pore-water sulfides for d34S analysis using secondary ion mass spectrometry. These compatible isotopic and microbial datasets offer valuable context for the laser Raman collected pore-water profiles and, applied in combination, have the potential to advance understanding of the microorganisms and metabolic processes underlying carbon and sulfur cycling at sub-millimeter resolution within deep-sea methane seeps.
Leg 1, Day 10: Our last foray to the seafloor
May 14, 2013
We did a morning dive at the San Diego Seep site, which is 42 kilometers (26 miles) due west of La Jolla. The potent fluids and gases seeping there create bacterial mats and chemosynthetic communities, and it made for a convenient last dive for this expedition. Read more...
Leg 1, Day 9: Good things come to those who wait
May 13, 2013
Today we went back to the alternate Santa Monica Canyon Mound site. This site had a large clam field with bacterial mats. Read more...
Leg 1, Day 8: Sampling pore water
May 12, 2013
The sites south towards San Diego left much to be desired in the chemistry department, therefore, Peter Brewer decided that we should head back to Santa Monica Basin. There was still one site there that had never been visited, and this area would give us the opportunity to revisit sites where we had previously confirmed fluid flow. Read more...
Leg 1, Day 7: You can't always get what you want
May 11, 2013
Today we conducted two half-day dives. Despite Chief Scientist Peter Brewer’s hopes, we found only carbonate rock, basaltic rock, and sediment. There were no signs of fluid flow, chemosynthetic communities, or gas venting. Read more...
Leg 1, Day 6: Decision making
May 10, 2013
Every evening, Chief Scientist Peter Brewer is faced with a decision—what will our mission be for tomorrow? Of course, a cruise plan was made many weeks ago, but when it comes to research expeditions, plans often change. Read more...
Leg 1, Day 5: There and back again
May 9, 2013
Much of this expedition has entailed exploring new areas of the seafloor. The high-resolution maps made by the mapping autonomous underwater vehicle (AUV) give the scientists a good idea of sites that may be of interest to chemists, geologist, and biologists—but we never really know what we’re going to find until we get there. Read more...
Leg 1, Day 4: Santa Monica Slope
May 8, 2013
Today we explored another new site based on the maps generated from the autonomous underwater vehicle (AUV) expedition on the Rachel Carson in March. This site was an elongated elevation with two distinctive peaks on the map, but we didn’t know if there would be any active venting here. Read more...
Leg 1, Day 3: Santa Monica Mounds
May 7, 2013
This site truly is a dream come true for deep-sea chemists and microbiologists. The large mound is covered in acres of ghostly undisturbed bacterial mat. The huge swaths of white bacterial mat and occasional patches of bright yellow/orange make the seafloor look otherworldly. Read more...
Leg 1, Day 2: Santa Cruz Basin
May 6, 2013
The weather improved immensely and we were greeted by sight of the Channel Islands this morning. Read more...
Leg 1, Day 1: Transit to Southern California
May 5, 2013
Today, we left the dock at 0700 to make our transit to southern California. Although the weather was beautiful in Monterey Bay, as we turned south, we steamed head-on into high winds (well over 30 knots) that are expected to persist all day. Read more...