PULSE 53: Pelagic-Benthic Coupling and the Carbon Cycle
September 17 - September 23 , 2007
September 18, 2007
Mike Vardaro and Jim Birch write:
Constant creaking, clicking, and the 24hrs/day rumble of diesel engines were the sounds that accompanied all of us on our first evening of sleep on the R/V Western Flyer. Having never been on this ship before, all sights, sounds and smells were new and unusual.
Today I awoke at 5:30am to observe Ken Smith's science team attending to the FVGR (Free-Vehicle Grab Respirometer) for a pre-breakfast deployment. The crew has told me that the weather for station M is 'normal', meaning 10 foot swells, increasing winds in the afternoon, and the predicted deterioration as the week progresses. We are closely watching the weather, as it determines when and if we can deploy the Remotely Operated Vehicle (ROV), but for now the weather is breezy but sunny and balmy.
The FVGR described yesterday by Mike falls by its own weight to a depth of over 4000meters. The (relatively) lighter flotation racks are streamed out behind the ship by hand, and then the heavy instrument is lifted over the water by a crane and released to sink to the seafloor. Once the FVGR was off the ship, space on the launch deck became available for an 'elevator'.
An elevator is a large basket-like container that drops to the ocean bottom with no connection to the surface. We can load any variety of instruments into this elevator and then send the ROV down to retrieve the instruments and perform experiments. Despite a large swell, the Western Flyer crew deployed the elevator with aplomb. In it were 'spreaders' from the lab of Dr. Ursula Witte to test microbial and microfaunal growth in sediment enriched with algae. The algae are radioactively labeled, allowing it to be traced later in the laboratory. The attempt to send the ROV down was postponed until after lunch, hoping the seas would be calmer. The weather did eventually cooperate, and the ROV was launched without event (aside from some sloshing of waves through the moon pool).
Unfortunately, there were some problems locating the elevator once the ROV had reached the bottom. This is always a possibility because traveling from the surface to 4000 meters, ocean currents can carry an instrument a long way from where it was launched on the surface and once on the seafloor it can be hard for the ROV to pick up the signal of the acoustic pinger attached to the instrument. The elevator was finally found just as the dive had to end; in order to get the ROV back on deck before dark, it had to be recalled before the spreaders could be deployed. Unpredictable weather and long hunts for equipment are all part of working in the deep ocean, and with luck we'll be able to get the samples tomorrow after we recall the long-term time-lapse camera mooring.
The 6 meter swells that we're currently experiencing may make that difficult, however...