7 March - 13 March 2011 (CAMBIO)

In the Antarctic the time flies by.  With astonishment we state that at this time, after the fifth week, half our expedition time is over.  The weather has been less kind to us, however, as we have had problems with bad visibility rather than with the sea-state.  Miserable sight condition due to fog or heavy snow impedes reconnaissance and slows down our steaming through the ice-fields, making it impossible to find lagoons in the ice where we can work.  Thick ice-fields and drifting growlers endanger wires, cables and instruments.  High swell brings water on deck and lets gear, such as the multicorer (MUC) or Dieter’s magic gear (MG), swing dangerously on the winch cable.  The bongo or light plankton nets can fly like kites in the high winds.  Heavy pitching of the aft deck impedes work with the MUC and ROV as the ship’s movement causes their position to vary in relation to the seafloor.  Although the weather impedes regular work on “Polarstern” less than on other ships it has to be taken into account as it is still a serious factor under Antarctic conditions. 

At the beginning of the week we continue our catches and ROV video transects in the Larsen B area.  We find a conspicuous contrast between the miserable catches of the AGTs, which are largely full of mud and stones with the only noticeable animals being brittlestars and shells of small scaphopods, and the ROV pictures from 160 m.  The ROV moves along the coralline and ground shell substrate with many larger stones that have obviously been there quite some time.  They are colonised over and over with pink and white hydrocorals, bryozoans, gorgonians resembling bottle-brushes, worm tubes and grey encrusting sponges.  Upon these organisms, and even on ascidians, sit isopods keeping their legs with the filter combs into the current to catch particles.  In the lights of the ROV we see quince yellow and vivid green sponges amongst the shell and debris between the stones, and once the lights of the ROV pick up an octopus coloured the same pink as many of the hydrocorals.  The motile crinoids here have extended their arms and tube dwelling worms have extended their tentacle crowns to filter food from the current.  Different sea urchins, of the short and long-spined type, and ophiuroids are sitting in large numbers between the stones.  A large sea star is spotted eating an adult sea urchin.

On Thursday morning we are back in Larsen A.  It is even darker than on the previous days.  It is snowing heavily but the storm that was announced to us seems to have changed its mind.  We lie close to the shore between islands, whose steep slopes resemble those of Norwegian fjords.  Because of the snow cover it is not always clear what is land and what is iceberg; also on the icebergs there is often sediment or stones.

The large AGT gets stuck on the seafloor and pulls wire from the winch, but comes free and the net remains intact, although with only 10 animals, mostly brown echiurids.  The yield of organisms is once again extremely low.  The small AGT is deployed immediately afterwards and brings up from 300 m a tonne of mud and stones which cost us 2 hr of washing and sieving, but which also yield a more representative catch of organisms.  The young researchers are sieving the material with great enthusiasm, interrupted with occasional snowball fights. Echiurids, small bivalves and tube-dwelling polychaetes dominate the catch.  Organismic density this close to glaciers is extraordinarily low.  We see that also on the video of the MG from 200 m, which shows fine, grey sediment from the glaciers’ abrasive action on the bedrock, and many stones.  The holes in the sediment with an earth-wall around are likely to be the dwellings of echiurids, which throw out the digested sediments.  The storm remains absent.  The explanation of the meteorologists is that we are in the eye of the low-pressure system.  The snow ceases, the sea around us is covered with a thin layer of new ice with snow cover on top.

On Friday there is more light and it remains quiet.  We conduct a ROV at 140 m at the station Larsen A south, close to the shore, which replaces the ROV that was cancelled due to weather the week before.  Close to the seafloor a lot of krill is observed swimming around the lights.  The community is similar to the previous station at Larsen B, but medium sized glass sponges are more common, with some younger ones seen less frequently.  However the stalked ascidians, which Julian found here a couple of years ago as an almost mono-specific community have practically disappeared.  In general this community has reached 1.5 decades after the collapse of the ice shelf a fairly high state of development, showing considerable biodiversity.  Special attention finds a demersal yellow ctenophore which is fishing plankton with long tentacles.  Its relatives all have a pelagic lifestyle.