Thursday, November 10, 2011

GETTING DOWN TO WORK

We heard the ship’s alarm at 0600 – and were delighted to be waked up this way! The weather had cleared enough to finish off-loading the cargo, including a large aluminum landing craft blocking the operation of the winch, and we were ready to go! The lines were dropped at 6:45 am (Fig. 1), and we got underway, steaming through the channel leading to Bismark Strait. Several small groups of penguins were on the small island across from the station. We headed east for the Neumayer Channel and then into the Gerlache Strait, heading back again toward our Station #22.

Figure 1. Lines were dropped in the early morning as we depart Palmer Station. Photo Peter Wiebe
The scenary was stunning and uniquely Antarctic (Fig. 2).  Sun was peaking out from behind the clouds giving rise to great highlights on the black rock walls along the channel and the thick sheets of ice and snow that cover most of the mountains. Shear cliffs of the ice several hundred meters tall mark the waters edge along the channel. Winds in the channel are much lower than in the open sea and are now less than 10 kts.

Figure 2. Our return passage through Gerlache Strait: a sparkling blue-and-white morning!  Photo Ann Bucklin
As we approach Stn #22, the MOCNESS was moved out to the stern, positioned for deployment, and given a last check by an Electronics Technician (ET; Fig. 3). All members of the science and RSCP technical teams worked this station. The station location was over a deep trough in the main channel that goes down to 1000 m. Our plan for the station work includes a CTD cast to 1,000 m, an IKMT tow, and finally the MOCNESS tow. Weather conditions looked good for our first station; the seas were very nice and the winds were light.

Figure 3. George Aukon (LMG ET) checks out the sensors and instruments on the MOCNESS. Photo Peter Wiebe
The station work proceeded according to plan and – as expected for a first station – everything takes an extra bit of time. The CTD cast was deployed from the Baltic Room through a huge door that opens in the side of the ship (Fig. 4).  The CTD rosette carries Niskin water bottles that can be “tripped” or opened at specified depths.  We tripped two bottles at each of seven depths from the surface to 1,000 m. The water samples were collected by the science teams (Fig. 5), and the water was filtered immediately for analysis at the UConn and SBU laboratories for chlorophyll, nutrients, particulates, and C:H:N ratios. Such biological characterization of the water column is critical to understand the “ecological niche” of our target species, the Southern Ocean salp, Salpa thompsoni.

Left, Figure 4. The CTD rosette with Niskin bottles deployed through the Baltic Room door of the ship. Photo Peter Wiebe. Right, Figure 5. Paola Batta-Lona (left) and Chelsea Stanley collect water samples for analysis from the Niskin bottles. Photo Ann Bucklin.
Immediately after the CTD cast, an Isaacs Kidd Midwater Trawl (IKMT) net was deployed from the stern and recovered after a tow to 175 m (Fig. 6).  This net is particularly useful for collection of living zooplankton, especially the fragile gelatinous salps that is the focus of our study. The catch in the IKMT was pretty light, with juvenile krill, amphipods, and several ctenophores and jellyfish, but no salps.

Figure 6. Deployment and recovery of the IKMT off the stern of the ship.  Left: A winch is used to lift the net over the stern gate of the ship, guided by the Marine Technicians (MTs) and scientists. Right: The recovery was made in calm seas; you can see the pentagonal mouth opening of the IKMT as it reaches the surface.  Photos Peter Wiebe.
After a break so everyone could eat dinner (quickly), we finished the setup and checkout of the MOCNESS and started the tow about 7:30 pm.  The MOCNESS can be controlled from computer on the ship, with commands sent down the conducting wire to the net. During the descent or downhaul, the first net, Net 0, was opened. At the bottom of the tow (at 822 m), a computer command was given to close Net 0 and open the next one, Net 1. During the uphaul, a total of eight nets was opened in succession to sample discrete depth strata through the entire water column: 822-600, 600-400, 400-200, 200-100, 100-75, 75-50, 50-25, and 25-0. The tow was carried out without difficulty and the MOCNESS was recovered about 10:30 pm (Fig. 7). No salps were caught and most of the zooplankton – juvenile krill – was in the upper 25 meters.

Figure 7. Left: Peter Wiebe (left), Joe Warren (center) and LMG Marine Technicians (MTs) ready for the MOCNESS for deployment at our first station. One cod end (in green racks) is attached to each of the nine nets. Right: The MOCNESS is recovered over the stern gate, requiring coordination by the Mate driving the ship, winch operator, and MTs. Photos Ann Bucklin.
Our work at Stn #22 – including clearing our gear off the deck, filtering the water samples, splitting and preserving the zooplankton samples, updating our data records and event logs, and cleaning up the shipboard laboratories – continued for several hours. We finished up just in time for “mid-rats” or Midnight rations, served for the ship’s crew, technicians, and scientists, who work as teams 24 hrs a day. After a quick debriefing in the mess, we headed for bed, while the Gould set course back to Cape Shirreff, a 9-hr steam. We hoped for good weather to allow the scientists to disembark via Zodiac and set up their summer camp.

-- Ann Bucklin (University of Connecticut)

1 comment:

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