Pelagic-Benthic Coupling 2014 Expedition

Chief Scientist Ken Smith
October 12-15, 2014

MBARI’s Benthic-Pelagic Coupling Group, led by Chief Scientist Ken Smith, is currently working on the R/V Western Flyer at Station M, located 200 kilometers off the coast of Santa Barbara, California. This week marks the 64th research expedition dedicated to an abyssal time series study at Station M. Since 1989, studies at this site 4,000 meters deep have produced insights into changing conditions in the deep sea. The research group is studying carbon supply to deep-sea ecosystems, and benthic community responses to food supply.


Finishing up at Station M
October 15, 2014

Today Ken Smith’s group completed their work at Station M. They conducted ROV transects and recovered two grab respirometers, which measure respiration rates of animals in the sediment, and then scoop the sediment into the grab so the animals within the sediment can be identified and enumerated. The grabs are put on the benthic elevator to be recovered because carrying them with the ROV is impractical. The elevator is then acoustically released and recovered by the ship’s crew two hours later once it travels the 4,000 meters up to the surface. Tonight, the Western Flyer is steaming 140 miles home to Moss Landing, California.

back of Western Flyer

—Susan von Thun

Sea pigs at Station M
October 14, 2014

The Benthic-Pelagic Coupling group uses ROV video transects as one method to study the community living on the seafloor at Station M. The Scotoplanes globosa, also known as the sea pig, is one of the most abundant animals in this area.

sea pig

The red dots are lasers set at 29 centimeters apart, allowing scientists to measure the size of animals on the seafloor.

Kathy Dunlop and sea pig

Kathy Dunlop, a postdoctoral fellow working with this group, is using ROV transects, as well as images from a stereo camera system and measurements of the animals from collections to calibrate size estimates among all of the methods.

—Susan von Thun

Camera tripod recovery
October 13, 2014

This morning the camera tripod and sediment trap mooring surfaced at 7:35 a.m., with an ascent speed ranging from 30-40 meters per minute. We can check the ascent speed by sending a specific acoustic signal through the water every minute. The acoustic instruments on the camera tripod receive this signal, and transmit its depth back to us, which registers on an acoustic receiver called a “deck box” on the ship. Even before we saw the mooring floating on the surface, the crew on the bridge of the ship could hear it ascend. The mooring has a float at the top (called a spar buoy) with a radio beacon attached. The crew tunes the ship’s radio to the special frequency emitted by the beacon—a frequency that we can only hear once the beacon is above water. When the crew hears a specific pulsing sound at that frequency, they know the mooring has made it to the surface, and we scan the horizon for it. The lab has several instruments with radio beacons. Would it be better for us to set up each beacon with its own unique frequency, or standardize them so that they all use the same frequency?

Camera Tripod recovery

Recovering the entire mooring requires patience, as each float pack (the orange blocks) and instrument is brought onboard one by one. Left, the crew recover one of the syntactic foam blocks, which are very heavy in air, but provide buoyancy in water. Center, the crew recover one of the two sediment traps. Once on board, the sample jars are carefully capped and put in the refrigerator for later analysis. Right, the crew recover the camera tripod, which is a large frame with the camera mounted on top and two strobe lights on either side.

—Crissy Huffard and Susan von Thun

Pelagic-Benthic Coupling Group at Station M
October 12, 2014

Today the remotely operated vehicle (ROV) Doc Ricketts dove to nearly 3,960 meters, where water pressure is extreme. On this dive, the team had the opportunity to fly by the Benthic Rover, which was deployed yesterday. On the ROV dive, we were able to confirm that the Rover was fully functional and had begun its mission. The Benthic Rover measures how much oxygen is being consumed by microbes and animals living in the sediments. In a series of experiments, the Rover measures how much oxygen seafloor animals are using. Precise motors lower two 30-centimeter-wide (12-inch) sample chambers into the sediment, where probes record oxygen levels.

Deploying the Benthic Rover

The Western Flyer crew gets ready to deploy the Benthic Rover. This panorama of the back deck shows all of the instruments which will be deployed throughout the expedition.

Just after sunrise this morning, the team deployed the benthic elevator, which can carry a heavier load than the ROV. Loaded with grab respirometers, it was deployed from the ship before the dive and left to free-fall to the bottom where the ROV would pull the equipment from the benthic elevator for use.

Electrical Engineer Paul McGill controls the science camera as ROV Doc Ricketts flies near the Benthic Rover. The research team was happy to see that the Rover was properly functioning.

Electrical Engineer Paul McGill controls the science camera as ROV Doc Ricketts flies near the Benthic Rover. The research team was happy to see that the Rover was properly functioning.

Tomorrow our first task is to bring up the camera tripod, which takes one picture of the seafloor every hour, for months at a time. (Watch a time-lapse video taken with the camera tripod.) To retrieve the camera tripod from a depth of 4,000 meters to the surface, we send an acoustic (sound) signal from the ship through the water, at a very specific frequency. This signal travels all the way to the seafloor, over two miles below. When it reaches these instruments on the camera tripod called acoustic releases, the signal triggers the release of a chain attached to a weight. This drops the weight and the camera tripod floats to the surface. Last time we recalled the system to the surface it ascended at a rate of 40 meters per minute. How long did it take to come to the surface from 4,000 meters? If I send the release signal at 6:00 a.m., what time should we start looking for the camera tripod on the surface?

—Crissy Huffard and Susan von Thun