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

September 17, 2007

Mike Vardaro writes:
After a late departure due to some technical difficulties, we are on our way to Station M, our deployment site. This abyssal site was chosen for a long-term deep-sea study because of the strong seasonal pulses of surface productivity in this area that can then be tracked as they fall to the seafloor and into the food chain of the animals that live there. Station M lies in 4100m (~13,000 feet) of water, roughly 200km off the coast of Point Conception, CA, so it takes most of a day to steam there from Moss Landing.

Deployment of Free-Vehicle Grab Respirometer (FVGR)The weather so far has been sunny and relatively calm, but given the unpredictable weather in this part of the Pacific we're not betting on it staying that way. The only excitement today has been preparing the FVGR (Free-Vehicle Grab Respirometer) for deployment and seeing some Pacific White-Sided dolphins.

The FVGR is a piece of equipment that drops down to the seafloor, sinks 4 metal grabs into the sediment and measures the oxygen levels inside. Then, after a two-day incubation, a timer triggers a current to pass through burn wires connected to the grabs. The current causes the wires to corrode rapidly, releasing the spring-loaded doors that close and trap the mud that the grabs are holding. We then send a signal from the surface that activates acoustic releases which drop the weights attached to the legs of the FVGR and allow the buoyancy of the 7 racks of syntactic foam flotation to pull it back to the surface. Once the FVGR has been found, caught with a grappling hook and hauled back on deck (assuming everything worked correctly... not always a safe assumption with complicated deep-sea machinery), the mud is cored and sieved to enable counting and species identifications of the tiny animals that live in the sediment. Several chemical tests are also performed on the retrieved mud. These measurements allow us to collect data on the respiration rates of the animals in the deep sea, and hopefully correlate it with the amount of food that settles to the seafloor from the surface waters.

We will also be doing an ROV (remote operated vehicle) dive with the Tiburon tomorrow to deploy some enrichment experiments from the microbiology lab of Dr. Ursula Witte in Aberdeen, Scotland. In order to get the FVGR deployed and get a full dive day in, we need to start attaching weights to and programming the computer of the FVGR at 5am tomorrow morning, and I'm very much looking forward to being on deck that early on my birthday. Hopefully I can stay awake long enough to celebrate later!

More news from other cruise participants tomorrow, ideally after a successful deployment and ROV dive!

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