Jul 18, 2011
The first half of NEPTUNE Canada’s maintenance and installation cruise of 2011 has gone really well. We are currently working at Barkley Canyon, the fourth of the five node areas that we plan to visit and are well on our way to accomplishing our cruise objectives.
Here is a summary from each of the node areas:
NEPTUNE Canada (NC) first travelled to the ODP 1027 area to complete the following objectives:
In September 2010, NC installed 2 of 3 trans-ridge cables that connect the node to study areas within the Endeavour Ridge Valley, specifically to the Main Endeavour Vent Field (MEF) and to the northern area of the ridge valley (RCMN location). The third node-valley cable will run south to Mothra Vent Field, and will be installed in September 2011.
Our first stop was at MEF where four instruments were installed in September 2010. They sent real-time data back to shore for a month, at which point we lost communications with the area. Such a problem could result, for example, from the failure of the junction box, cable, or a connector. Testing during this cruise has confirmed that the junction box works fine, which means the problem lies with the cable. Plans are to replace this cable in September 2011, which should then bring this suite of instruments online again (read blog).
While on-site at MEF, we also:
Next we headed to the Regional Circulation Mooring North (RCMN) location where 12 instruments by one mooring and a short period seismometer were installed in September 2010. During that cruise one cable failed and the cable originally intended to connect to Mothra was reallocated to RCMN. That was worthwhile as these instruments continue to provide quality real-time data to the scientific community. During this cruise we performed our first successful cable recovery. ROPOS cut the cable in half, then on separate dives, hooked into each portion of the cable and ascended to the surface. The cable pieces were then rolled onto the deck via the R.V. Thompson’s A-Frame. This difficult and delicate operation had to be done during calm daylight because while the ship was pulling up the cable it was tethered to the seafloor at 2300 metres deep!
Stopping at CORK (which NC will soon connect to, providing real-time access to the data), inspected the instrument platform, and deployed a CTD. We also recovered the Imagenex sonar, which was installed in May 2010 at Bubbly Gulch near the Bullseye Vent.
Our first stop was at the 400-metre upper slope area where we lost communication in February 2011 due to a possible strike by a trawler net. All instruments are present but most have been flipped over and will require advanced testing. There was extensive damage to the extension cable, which led to the loss of communication and will require a considerable repair effort (read blog). The team plans to retrieve all the instruments within a week so they can be tested and refurbished before an eventual redeployment next year.
We then visited the home of Wally the crawler, among the gas hydrate mounds on the wall of Barkley Canyon (870m). Wally was retrieved for cleaning and refurbishing, temperature probes were deployed, samples and experiments were collected, and a survey of the hydrate mound was carried out to document changes over recent months.
Finally, we recovered, maintained and redeployed Pods 1, 3 and 4 at the mid-canyon wall (900m), and canyon axis (1000m). Scientists are studying benthic (seafloor) ecology using suites of instruments on these and the Upper Slope Pod 2. Long-term monitoring will allow scientists to follow the seafloor response to pulses of food from the phytoplankton blooms of the surface waters, and observe changes in seafloor communities related to seasonal patterns of sediment transport and nutrient upwelling.
Sampling is needed to calibrate and to extend the footprint of our network. We have collected 51 out of the planned 75 push cores samples, along with water samples (suction and Niskin bottles) for researchers during the cruise. At MEF, samples of tubeworms were taken for comparison of the symbiotic bacteria with other symbionts of tubeworms found elsewhere (read blog).
We will remain at Barkley Canyon for the next while to focus on the recovery, inspection, maintenance and redeployment of instruments at all study areas there, including the upper slope at 400 meters, mid-canyon wall at 870-900 meters, and the canyon axis at about 1000 metres. The final stop will be maintenance at Folger Passage where we expect biofouling (things growing on our instruments) to be significant since it has been more than a year since our last visit to this one location in our network that receives sunlight. If time allows we will go back to Endeavour to do some surveying in preparation of the September cruise, and plan to dock in Esquimalt on July 26th.
All ROPOS dives are recorded and can be found on SeaTube.