Gulf of California 2012

Faults, Vents, and Seeps I

March 26-April 17, 2012

Most of the Gulf of California’s long, narrow seafloor basins are associated with transform faults, where segments of the Earth’s crust slide past one another. Throughout the gulf, transform faults alternate with volcanic spreading centers (see map here). Researchers will use the ROV Doc Ricketts to search along the transform faults for evidence of recent geologic activity on the seafloor, especially active faulting, underwater landslides, gas vents, or fluid seeps.

During these legs, researchers will first conduct a series of exploratory dives, looking at potentially active seafloor areas that have been identified using maps created by the MBARI seafloor-mapping AUV. They will be ground truthing the recently collected AUV maps and collecting physical evidence of recent geologic activity. They will return to specific sites to collect samples of seafloor fluids and seafloor animals for biological and geochemical studies to further investigate sites of seafloor fluid seepage.

Some of the specific objectives of these cruises will be:

  1. To identify individual transform faults and determine how active they are.
  2. To determine whether fluid and gas venting occurs uniformly along these transform faults, or if it is focused near volcanic spreading centers (ridge crests)
  3. To collect deep-sea tubeworms (a typical inhabitant of seafloor seeps) so that biologists can study the unique microbes that live inside these tubeworms. The microbes allow tubeworms to live off of chemicals in the seep fluids that would be toxic to most other animals. Biologists on the cruise hope to use DNA and RNA from the microbes to determine how they vary from one part of the gulf to another, and if they are related to the chemistry of fluids or sediments at individual seeps.
  4. To use an instrument called an In Situ Ultraviolet Spectrometer (ISUS) to automatically measure concentrations of sulfides in seawater and in seafloor sediments. Sulfides are one of the main food sources for microbes, tubeworms, and other animals that live around seafloor seeps. Researchers will compare the sulfide measurements at different seeps with the types of animals and microbes found at these locations. Also, by measuring sulfide concentrations at different locations and different depths in the sediment, the researchers hope to better understand the factors that influence how much and what types of fluids are seeping out of the seafloor at a particular spot.
Dive sites for the Faults. Vents, and Seeps research program.

Dive sites for the Faults. Vents, and Seeps research program.

Logbook

Close-up of cold seep clams with their siphons extended, clustered together on the seafloor.

GOC 2012: Apr 16

Our goal today was to search for patches with clams of varying sizes.
The ISUS instrument, held by the manipulator arm, measures sulfide coming out of this deep cave, newly named Jackson Hole. Tubeworms can be seen on the left inside the cave with bacterial mats all over the walls. The white edge at the top is carbonate rock outcrop and old clam shells.

GOC 2012: Apr 15

The ROV traversed up the side of this mound and we discovered an extensive chemosynthetic community surrounding a large fissure, or cave.
This huge sponge colony was perched on a carbonate outcrop. Many old clam shells were embedded in the surface of the rock.

GOC 2012: Apr 14

We spent the day studying dramatic seafloor rocks, intriguing animals, and seafloor chemistry around an area called Pinkie's Vent.
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.

GOC 2012: Apr 13

We traveled back to the northern part of the Guaymas Basin.
Ventral (under-side) view of a brooding polychaete worm called a syllid, about one centimeter (0.4 inches) long.

GOC 2012: Apr 12

Today we collected an interesting worm on the wall of the canyon amongst the tubes of a lot of other worms and hydroids.
The biologists collected this beautiful Acesta clam on our first dive today. It had a sea star and encrusting sponge on its shell.

GOC 2012: Apr 11

The biologists collected this beautiful Acesta clam on our first dive today. It had a sea star and encrusting sponge on its shell.
A bird's eye view of the gas sampler (held by manipulator arm) as it catches bubbles to measure gas composition at this site. The high-definition camera caught gas-hydrate coated bubbles on its housing.

GOC 2012: Apr 10

This dive was a great illustration of the combined impact of geological, chemical, and biological processes on the seafloor. All the scientists were excited!
We saw a number of these large sea spiders, or pycnogonids, lumbering across the seafloor. In 2010, MBARI researchers published their novel observations on sea spiders.

GOC 2012: Apr 09

When we reached the seafloor at 2,700 meters (8,860 feet), the first thing we noticed was how abundant and diverse the organisms were at this site..
A number of dolphins swimming in our bow wave provided the in-transit entertainment this morning.

GOC 2012: Apr 08

This low-oxygen seafloor in the Gulf of California might give us a glimpse into the future of our coastal oceans.
The science team, ROV pilots, and many members of the ship’s crew gathered around the ROV for a final group photo as the ship was steaming to port.

GOC 2012: Apr 04

The science team, ROV pilots, and many members of the ship’s crew gathered around the ROV for a final group photo as the ship was steaming to port.
A microscope picture of one of the snails we collected today.

GOC 2012: Apr 03

On this leg of the expedition, we have biologists who can take advantage of some of the geology samples to look for by-catch. Today, Shannon Johnson found some animals on rocks that were very interesting to her!
Longtime collaborators Charlie Paull and Juan Carlos Herguera process a push core for foraminiferans.

GOC 2012: Apr 02

Today we dove the ROV Doc Ricketts into a long linear trough only 15 meters (50 feet) wide at its base. This was barely wide enough for the ROV to turn around without banging into the sides of the trough.
One of the Western Flyer's engines that the engineers keep running smoothly day in and day out.

GOC 2012: Apr 01

It takes a well-oiled team to keep all systems working on the Western Flyer during this 97-day expedition.
One of the clams that we brought to the surface.

GOC 2012: Mar 31

Today was a very interesting day geologically and biologically. One of the most exciting moments was when we finally collected some clams!
Pinky the Easter bunny watches over the ROV shop while Knute fixes a part for the ROV.

GOC 2012: Mar 30

Science is an adventure. It is never the same and you can never count on anything, expect the unexpected and then the even more unexpected will happen!
We saw quite a few tripodfish on the dives today, which is a rare treat for us because we don't see them in the Monterey Bay region. They have long extensions of their fin rays that allow them to stand on the seafloor and wait for prey to swim by.

GOC 2012: Mar 29

What can you learn from a dead, single-celled organism buried in deep-sea mud? Almost everything!
Shannon Johnson picks animals off the sampled rocks.

GOC 2012: Mar 28

We collected a green volcanic rock covered in sponges and nereid and serpulid worms. Shannon Johnson picks animals off the sampled rocks.
Three species of foraminiferans from 2,200 meters (7,218 feet) depth in the Gulf of California.

GOC 2012: Mar 27

You might think looking at mud all day could be kind of boring. But, today was an exciting day of sampling.
R/V Western Flyer departing Bahia de La Paz.

GOC 2012: Mar 26

The expedition is now more than halfway completed and the R/V Western Flyer is once again transiting north through the Gulf of California from La Paz... this leg will primarily focus on the faults and seeps along the transform fault line where the North American and Pacific Plates meet.