Gulf of California 2012

Deep-Sea Chemistry

March 14-22, 2012

The primary mission for this expedition is to investigate the chemistry of the pore water—water that occupies the space between seafloor sediment particles—that surrounds various geologic features and active natural gas vents in the Gulf of California.

Peter Brewer’s research group will use as their primary tool a laser Raman spectrometer, which can bounce a specially-tuned laser beam off of almost any object or substance, and receive back a signal that provides information about that object’s chemical composition and molecular structure. This tool will allow the group to get chemical data back from the seafloor in real time.

In addition, the research team plans to take a series of push cores for pore-water sampling for comparison with the Raman and long-term studies. Gas and water samples will also be collected near the vents to study their impact on the local water chemistry, and for comparison with local gas hydrate compositions.

If natural oil seeps are found, the group plans to study oil droplets, measuring how quickly they rise to the surface. They will also measure the release of natural gas from the droplets as they transit up to the surface. This provides in microcosm a natural analogy of processes occurring at human-induced oil releases.

In addition, water samples will be collected using CTD casts for collaborators J. Martín Hernández Ayón and Gabriela Y. Cervantes from the Universidad Autónoma de Baja California in Ensenada, and for Joseph Murray and Abbey Chrystal—graduate students from University of California, Santa Cruz.

Dr. Hernández Ayón is studying the inorganic carbon system, ocean acidification, and biogeochemistry in coastal regions near Baja California and the Sea of Cortez with a special interest in the oxygen minimum zone. Joseph Murray is interested in the effects of coastal runoff and its impact on nitrogen-based nutrients. Abbey Chrystal is a paleo-oceanographer looking at the record of long-term changes in seawater pH recorded in the sediments.

Deep-sea chemistry research sites.

Deep-sea chemistry research sites.

Logbook

Jason Jordan, left, and Andrew McKee lower a fender into place in preparation for docking in Pichilingue.

GOC 2012: Mar 22

The Western Flyer arrived back at the dock before 9:00 a.m. today... it was a beautiful morning to be at sea.
ray

GOC 2012: Mar 21

Today was our last chance to search for unusual chemical signals indicative of fluids being forced through the seafloor in the Gulf of California.
Gabriela Cervantes and Martín Hernández Ayón with one of the push-core sediment samplers they took off the remotely operated vehicle. The two have had a few such mud samples to process every night; they carefully separate out sections of the core for later testing for trace metals.

GOC 2012: Mar 20

One seamount and one slump at the edge of the continental margin attracted our attention today. Like yesterday, some of the terrain kept us riveted to the video monitors.
benthic_1

GOC 2012: Mar 19

Today, the science team covered a lot of fascinating territory at a fracture zone. Large boulders, rubble, cliffs, a variety of animals; if the same territory was on dry land, it would be as beautiful as a national park.
This view from the main camera on the remotely operated vehicle gives an idea of the various sampling tools carried to the seafloor to conduct chemistry studies. The laser Raman probe in a specially designed tripod with a hydraulic actuator sits above a fissure lined with white and orange bacteria. In the foreground, from left are the thermistor at the end of the orange cable, used to measure the temperature of venting fluids; push core tubes used to collect mud from the seafloor; and the pump and gauges used for the precise operation of the Raman spectrometer.

GOC 2012: Mar 18

Different territory, different chemical activity. Today we moved to a transform fault—a spot where tectonic activity created cracks in the sea floor at right angles to the spreading center—and found methane and cold seeps, in addition to sulfur.
A thermistor is inserted into one of the fissures to measure the temperature of the venting fluids. They were clearly warmer than surrounding seawater, but not very hot.

GOC 2012: Mar 17

Persistence paid off today from searching an unexplored area of the sea floor with a beautiful outcrop covered with large patches of yellow bacteria-an indication of sulfur-laden water rising up from below.
We also saw this odd enteropneust. MBARI researchers recently published a paper on these unusual animals that are genetically more like humans than the worms they resemble.

GOC 2012: Mar 16

The best of explorers set out for points unknown making an educated guess about what they might find, but being open to serendipitous discoveries.
This soft blob of bacteria was pulsing with the flow of the fluid from below. The color indicates these microbes are feeding on sulfur, and the fact that no giant clams or tubeworms were seen in the area suggests that this is a fairly new fluid flow, as older vent sites are usually teeming with such life.

GOC 2012: Mar 15

At a depth of 2,700 meters (8,858 feet) we came across a pulsing yellow blob surrounding a hole in the mud. A creature straight out of a 1950s science fiction movie?
Research technician Peter Walz inspects the coil of tubing on the liquid-core waveguide prior to sending it down to 2,000 meters (6,500 feet) for testing. It looked perfect on deck, but when it got to depth, it wasn’t quite as good as hoped for.

GOC 2012: Mar 14

After three days in port to refuel, switch out some crew members, and mobilize the next group of scientists and their equipment, the Western Flyer set sail from La Paz early this morning.