PULSE 53: Pelagic-Benthic Coupling and the Carbon Cycle
September 17 - September 23 , 2007

The Equipment

Ship & Vehicle : R/V Western Flyer and the ROV Tiburon
(R/V = Research Vessel,   ROV= Remotely Operated Vehicle) 

    High Frequency Suction Samplers on ROV TiburonHigh Frequency Suction Samplers: ROV Tiburon is shown here outfitted with 12 buckets on a rotating carousel that form the collection portion of the High Frequency Suction Sampler (HFSS). This sampler acts like a vacuum cleaner sucking up samples and depositing them into one of the 12 buckets.Tiburon is on top of the moonpool within the R/V Western Flyer. Tiburon is lifted, the moonpool doors open and the ROV is launched and recovered through this area.

 

    Push Cores on Swing Arm Rack Push Cores on Swing Arm Rack: ROV Tiburon also carries two instruments that sample sediments. One is called a push-core, and 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 ROV Tiburon’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.

 

    Benthic ElevatorBenthic Elevator: The benthic elevator allows us to carry more than the ROV itself can carry. Loaded with sediment enrichers, it is deployed from the ship before the dive and free-falls to the bottom where the ROV pulls the equipment from the elevator for use. After the ROV is recovered, the elevator anchor's acoustic release is triggered from the ship, and the elevator freely ascends to the surface and is recovered.

 

    Deployment of Long Term Sediment TrapLong Term Sediment Trap: Sequencing conical sediment traps, each with an effective mouth opening of 0.25 m2, are moored at 600 and 50 m above the bottom at 3,500- and 4,050-m depth, respectively (Baldwin et al. 1998). Trap sequencers are programmed with a sampling resolution of 10 days to collect sinking particulate matter in sampling cups poisoned with 3.0 mmol HgCl2. In the laboratory, the collected particulate matter is analyzed in duplicate for total and inorganic carbon, with organic carbon determined by difference following methods described by Baldwin et al. (1998).

 

    Retrieval of Camera Mooring Camera Mooring: The time-lapse camera system was first deployed at Station M in 1989 (Smith et al., 1993), and has since collected 27 time-lapse image data sets of approximately four months each. The camera takes one still photograph of the seafloor every hour and the film is recovered and the equipment redeployed during maintenance cruises 3 times a year. The time-lapse camera consists of a Benthos 377 camera mounted on a titanium frame at an angle of 31º from horizontal with the lens ~2 m above the sea floor. The camera is equipped with a 28-mm Nikonos lens, providing angular coverage of 50º in the horizontal and 35º in the vertical plane, and holds 400 feet of 35-mm color-negative film (Fuji, Type 8514, 500 ASA). Up to 3500 images can be collected in 4.6 months. Two 400-W-s strobes, one mounted on either side of the camera housing, illuminate approximately 20 m2 of the sea floor beginning at a distance of 1.8 m from the camera frame and extending approximately 6.5 m from the base of the camera frame (see Smith et al. 1993 for a more complete description of the time-lapse camera). In June 2007 a high-resolution digital camera was added to the frame. The camera is housed with a PC104 processor and external memory drive. These components are used to control the camera and store images. Additionally, in the same housing are a low power controller (Persistor CF2) and an electronic interface board to control power to the PC104 stack, camera, and strobes.


    Benthic Respirometer Benthic Respirometer System (BRS):
    Oxygen consumption (a measure of biological activity) of the organisms living in the sediment is measured using a Benthic Respirometer System (BRS). This instrument is used in situ (in place on the seafloor).

 

    Free Vehicle Grab Respirometer (FVGR) Free Vehicle Grab Respirometer (FVGR): Oxygen consumption (a measure of biological activity) of the organisms living in the sediment is measured using a free vehicle grab respirometer (FVGR) with grabs that retrieve the sediments for faunal examination and chemical analyses.

 

    Benthic Rover
    The benthic rover during tests of the drive mechanism at about 3,300 feet depth in 2006. The rover is headed to the left; the bare poles on its front will hold sensitive respirometers when the vehicle is connected to MARS. Image ©2006 MBARI.
    Benthic Rover: The rover is a mobile physiology lab. In a series of experiments, the rover measures how much oxygen seafloor animals are using. Precise motors lower two 30-cm-wide (12-inch) sample chambers into the sediment, where probes record oxygen levels. Two acoustic scanners use ultrasound (in 4-MHz pulses) to look 10 cm (4 inches) deep into the sediment for large animals like worms.
Diagram of the Benthic Rover

To measure metabolic activity in the sediment, twin respirometry chambers isolate samples of seafloor for 3 days at a time. Agitators stir up the sediment while sensors record oxygen levels. Diagram: Ken Smith, MBARI.
Diagram of the Benthic Rover's optical/acoustic scanners
The rover also has two optical/acoustic scanners that detect active chlorophyll and animals like worms buried up to 4 inches in the sediment. These two pieces of information help to fine-tune the respirometry measurements and to determine how quickly sediment arrives. Diagram: Ken Smith, MBARI.