Umitaka Maru – CEAMARC voyageWeek 3 — 6-12 February 2008Dr. Graham Hosie is onboard Umitaka Maru, the last of three Census of East Antarctic MARine Cruises (CEAMARC) voyages for Season 2007/08. These situation reports (sitreps) are by Graham Hosie (CEAMARC Leader), Takashi Ishimaru (Voyage Leader)
6 February 2008We made several attempts to find good anchorage stable enough to allow calibration of the echo-sounders. Most of the ground around Dumont d'Urville is hard rock and the anchor drags.
One attempt at calibration was unsuccessful with the calibration line (fishing line) going under the hull being cut by ice floating past. This at least happened before the calibration ball, a small metal sphere of known acoustic properties, was lowered down the line.
Five gentlemen for the French Antarctic institute IPEV visited the ship. These included the captain Stanislas Zamora and bosun Alain Pottier from l'Astrolabe who were on the previous l'Astrolabe CEAMARC voyage, as well as the postmaster from Dumont d'Urville. Later met with Yves Frenot, Deputy-Director IPEV and discussed progress with CEAMARC.
Currently, we are making one more attempt to anchor securely. If unsuccessful, we will return to our offshore sampling sites and hope for good weather. Latest satellite pictures show high chlorophyll concentrations between DDU and the Mertz Glacier.
8 February 2008Completed 2 stations in the last 24 hours and half way through another at present. Both the RMT and IYGPT nets returned high abundances of larvae and juveniles of Pleuragramma fish. Typically, the new larvae and the one year old group are found in surface waters and older specimens going deeper with age. The third and fourth year groups are common in the 200 m trawls and we need to go to 500m to catch the adults.
The fish look somewhat like a sardine or pilchard although they are commonly called Antarctic herring. These fish are an important food item for the higher predators such as Adélie and emperor penguins.
The high definition video camera on the VPR captured excellent images of the young Pleuragramma larvae darting about feeding.
The wind continues to blow off the continent, bringing very cold air. People new to the Antarctic quickly understood the meaning of wind chill. In the afternoon, it was sunny with a temperature of -4 °C and almost no wind. It was quite pleasant on deck. By late evening, the temperature dropped a few degrees and the wind increased to over 20 knots giving a -25 °C wind chill, and making work on deck difficult. Nets are freezing and need thawing before deployment. Samples are starting to freeze before processing.
9 February 2008Completed all the stations along the west-east 66 20S transect and now heading SE towards the base of the Mertz Glacier in Buchanan Bay to start the northern run along the 143E longitude transect. The weather has remained very good, although somewhat cold on deck, allowing us to make good time.
Some of the electronic gear are having difficulty working in the sub-zero temperatures. The VPR has to be de-iced before deployment, the RMT net release needs to be warmed up so we can set the net trigger to open the nets, the deep sensor is not working properly and we need to be careful that some of the sensors on the CTD do not freeze.
The net catches continue to produce plenty of Pleurgramma larvae and juveniles and the occasional ice fish larvae.
The next station will be interesting. Super-chilled seawater at about -2.1 °C comes out from the base of the glacier near our sampling station. When the Aurora Australis sampled here in winter 1999 we got full of flat ice crystal about the size and shape of 15mm diameter coin produced by this super-chilled water.
10 February 2008We reached our southern most station in Buchanan Bay at the base of the Mertz Glacier. We arrived in clear blue skies with the glacier stretching from the south to the north-eastern horizon. We also arrived during a period of strong katabatic winds coming off the continent bringing cold air of -10 °C with a wind chill of -30 °C.
Work on deck was fairly cold at first but the katabatic soon eased to a pleasant day. New sea ice was forming around us, initially grease ice, which then consolidated into a pancake ice of 10-30 cm diameter.
Unfortunately, much of the electronic equipment refused to operate in the cold conditions. We still managed to sample the full range of the water column in the Adélie Basin at a depth of 800m but returned very few biological specimens compared with other sites. There was less phytoplankton, some crystal krill and some Pleuragramma and icefish larvae.
We completed one more station last night before bad weather caught up with us. We are now experiencing winds in excess of 40 knots and a very high wind chill factor outside. There is no work on deck today. We wait at the third station on the south-north transect for the wind to abate.
11 February 2008Good weather returned late yesterday afternoon and we are now making the best of the conditions to get as much sampling done before we depart the region tomorrow night.
We completed sampling of the Adélie Basin last night which showed a large concentration of phytoplankton and high abundances of ice krill and Pleuragramma fish. Several species of ice fish larvae were also caught.
The zooplankton team continue to capture good images on the VPR. It is much more interesting to see some of the big jellyfish in their natural state, rather than in the bottom of a bucket.
We are currently sampling the middle of the trough that connects the Adelie basin to the continental shelf slope.
12 February 2008The good weather yesterday allowed us to complete two stations, one in the trough between the Adelie Basin and the continental shelf slope, and another on the shelf slope 16 nautical miles further north. The latter station was close to a thin band of pack ice that extends west from the region east of Mertz Glacier. The continental slope is moderately steep here and in just a few nautical miles the sea floor had dropped to 2000m.
Antarctic krill was very abundant here along with a number of ice fish and myctophid (lantern fish). We also caught an excellent specimen of the fish Anotopterus vorax, about 60 cm long and looking like a long slender barracuda. The community on the slope is quite a different to the shelf community a few miles south.
The trough station produced very large numbers of Pleuragramma fish whereas they were more-or-less absent in the slope station.
We are now at our last sampling station 15 nautical miles north of the slope station. We will be sampling this site with all sampling gear on board. We expect to finish late tonight.
We'll then head for Hobart with the continuous plankton recorder streamed behind and this will be our last piece of sampling.
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