Weekly Report ANT XVII/3-3 (01-07/04/2000)

Whilst I'm writing this report, we are once again in the firm grip of the next low at Austasen. "Polarstern" has turned her head a safe distance from the icebergs and is drifting slowly in these force 10 winds and snow flurries, from time to time steaming forward. We have to stop work for another night because the visibility is sorely pitiful. Apart from this we have no other problems because we are in the middle of an ice field and in the lee of the icebergs, and the waves are only reaching a moderate height of nearly 1 metre - pretty much the same as we have experienced all week. The effect of the sea ice (admittedly to the sorrow of our pancake scientists - because the ocean is acting as a heat source and the ice is tending not to thicken) is dramatic: the fragile ice fields were torn up, wide areas of free water developed, and ice needles are starting to grow along the windrows. The ice needles (frazil) develop into grey fields that have a surface like sharkskin and, through continuous cooling, become "grease-ice". In this layer small pancakes can form, which subsequently grow into bigger floes as the seawater loses even more heat. In calm weather a closed layer of sheet ice with its snow blanket develops without pancake formation and this was the situation in the area in which we worked prior to the storm. This layer is disturbed by wind and waves again and again, disintegrating into small floes, distributed over a large area, and contributes (according to Max) to the loss of the heat of the ocean. At present, the ice boundary of these thin floes is already far to the north as the satellite pictures show. Meanwhile, near to the continent, the ice cover is considerably thinner.

We were quite shocked by the enormous activity of the icebergs around us. At this time of year there are series of areas of intense low pressure. They come from the Antarctic Peninsula, at best one week apart, and wind forces of 10 to 12 commonly accompany them. They bring, probably in connection with the tides, the stranded icebergs back into circulation again and again. Meanwhile the navigator of "Polarstern" has accepted this problem and has produced drift maps that make our hair stand on end. A supposed stranded berg of 250 m length has begun to move single-mindedly in the direction of Dieter's mooring, which we can't retrieve because of the storm. Admittedly, the perpetual scratches have a rather positive biological effect: here, in contrast to Kapp Norvegia, the big old sponges and the dense bryozoan thickets are missing, but the faunas in both areas are diverse. Boris and Igor counted over 200 macrofauna species from each trawl just with their eyes and the species richness of Lucy's sea stars (classical disturbance indicators) is amazing - about thirty per haul. Only one species inhabits the north German Wadden Sea and the mid-Baltic. Between both the lows in the last week we've had balmy weather. Although it's been bitterly cold with temperatures below minus 20, we've had bright sunshine and unforgettable dawns and sunsets in the grandiose iceberg cemeteries off Kapp Norvegia, in Four Season's Inlet (where the glacier has been calving), and even yesterday evening when we arrived at the iceberg cemetery at Austasen where we will spend the next few days. Innumerable metres of film were shot so as to catch the changing light on the icebergs and the shelf ice edge: from snow white, through rosy pink to a deep red in the evening until the disc of the sun finally sinks below the horizon - and in the morning the exact reverse.... And last night, before the weather changed, one last gift - Southern lights in green, red and white in the heavens. How can we digest all this? Naturally, we have been amazed in this third week of our EASIZ cruise - not only by the wonderful Antarctic landscape but also by the rapidly changing weather. We have worked on our topics "not very heavily disturbed bottom faunal communities off Kapp Norvegia" and "shallow water communities in the Four Seasons Inlet" with all gears as systematically as is possible with these weather conditions and we've started with the project "heavily disturbed communities in Austasen". We are also attempting some other topics of our chore programme (benthopelagic coupling, the effect of iceberg disturbance on benthic and fish communities, biodiversity, autumn aspects of population dynamics, physiology and reproductive biology, identification of marine natural products) at the same time. Over the day we deploy the heavy gears like the trawl, multibox corer, giant box core and TV grab for which we need an extensive deck crew. In the night, we deploy lighter and less personnel intensive gears like the CTD/Biorosi, Bongo, multinet, Rauschert-Dredge, ROV and photosledge, or we steam over the ground we're going to trawl the next day to check it out, so as not to waste our precious daylight hours. As long as the temperatures are only a few degrees below zero, like they were on some occasions at the beginning of the week, we shouldn't experience too many problems with the gear, but at minus 15 to 20 degrees, especially when these are accompanied by strong winds, things can become critical. An armour plating of ice forms on anything metal: the mechanism of the giant box core fails and the ROV freezes, although sometimes a warm water hose or a fan heater under a tarpaulin can help. Trawls freeze solid, faster than you can see, and living material can only be rescued if it's rapidly immersed in buckets of sea water. The thick sediment from the TV grab freezes overnight to an ice block, which has to be cracked into small pieces with a pick axe the following morning. The deck crew and the scientists wrap up well and clench their teeth against the biting wind and fingertips that hurt even through gloves. Daffodils in Europe? May be, but down here there is material for PhDs, lots of interesting papers, and good collaboration. Let's do it!

We are already beginning to crystallise new ideas. Stefano noticed that an amazingly large number of benthic organisms are releasing larvae or brooding young at this time of year; for example, the soft coral 'Ainigmaptilon', several Actiniids, two sea stars, and Cova's lollipop sponges. Perhaps the release of larvae and juveniles in spring is related to the plankton bloom in the water column only for those species with pelagic larvae? Josep-Maria suggests that the budding shown by a lot of the suspension feeders may be an alternative to sexual reproduction and larval recruitment and may hasten the process of recolonisation after iceberg impacts; "cloning" of young animals must be investigated. The shallow water fauna at Hilltop, where Martin has found another new spectacular amphipod with red and white tiger stripes, has striking similarities with the isolated fauna of the Lazarev Sea. Is this relict fauna from a former time when the littoral zone around Antarctica was both larger and ice free?

We have to solve these and many other questions. Please, cross your fingers that the weather will improve quickly so that we can get back to work again.

Best wishes,

Wolf Arntz