Report 8: Return to the ice

Jade iceberg
The open sea is not all dull clouds and waves (Photo: Steve Nicol)
Krill from marine science trawlNewly-shaved yogis

Steve Nicol, Voyage Leader

After a few days exiled out in the grey open ocean we are once again back in the sunlit sea-ice zone. The advantage of this sort of survey is that you are guaranteed a dramatic change of scenery at least once a week. At this point in the voyage we are into a nice easy rhythm and mark the passing of the days by the regular lowering and raising of the CTDs and the other instruments. Days pass and the stations on the route map slowly get ticked off and suddenly you realise that you have been at sea for 4 weeks – and we must be enjoying ourselves because time is flying. The question now is not so much how much more must we do, but rather have we enough time to do all the things we need to?

We are now approaching the coast at 40°E in an area close to the Japanese base of Syowa and we have been informed that the icebreaker Shirase is there and is likely to leave shortly. Because of time constraints, however, we will merely be able to wave as we go past and move on to the next transect at 45°E.

Much of the work that we are doing out here is to try to build up a composite picture of the ecosystem in this vast area of ocean. This is a remarkably difficult undertaking given that we are only able to sample in a very restricted number of places. We need to be able to get information on the abundance on organisms and be able to relate this to the oceanographic conditions, but perhaps the more difficult task is determining the productivity of the plants and animals because it is this which determines how much energy can be passed on to the next level of the food chain.

For the algae, the grass of the sea, we have a couple of techniques that give quick indication of what state they are in and how much carbon they are taking up. But this is only part of the microbial puzzle because some of the unicellular life forms are actually predatory on others and even more confusing still, some of them can act like either plants or animals depending on the ambient nutrients and light. What becomes available to the herbivores is a mix of what is left once the microbes have finished with the plants, and of course the microscopic animals themselves are a food source in their own right. Determining what is being produced by which element of the microbial community requires a combination of complex instruments, experimental manipulations and a highly focussed if somewhat explosive group of scientists. We have a series of large, slightly flammable vats in which a brew of the local microbial community is grown and manipulated so that their production and dynamics can be better understood. In some, herbivores such as krill are added to see what effect grazing has on the community structure. As krill is a major focus of this voyage there are also convoluted efforts to understand their productivity.

Some of this information can come from preserved animals, which provide insights into the previous growth and development through the distribution of size classes present in the population. But to find out more about the growth of the krill under local environmental conditions we need to conduct experiments and this is where the krill Hilton comes in.

Krill grow by moulting, and every month or so they throw off their old shells and grow into a new one so it is possible to determine how fast they are growing by measuring the size difference between the old shell and the new one. It sounds easy but because moulting occurs only once every month, and Natalie has ingeniously calculated that only one in 30 krill will moult every day so, to get a good handle on how fast the population is growing, we need dozens of measurements, all taken within a few days of capture so that the exhibited growth reflects local conditions. This means keeping hundreds, and often thousands, of healthy krill in individual jars in our container laboratory on the trawl deck and checking them daily for moults. So, when a trawl bulging with krill comes aboard the krill crew are to be seen heading for the container with buckets of experimental animals and they spend the next few hours bottling krill and placing them in the elaborate facility designed by Rob King who, realising the labour intensive nature of the apparatus he designed, wisely stayed behind in Kingston. The hard work will pay off though with the best ever description of the condition of krill over such a wide area of ocean and a better understanding of how the production of these key herbivores is related to the overall productivity of the ecosystem.

On board the Aurora, Australia Day was well-celebrated with a traditional BBQ, several entertaining krill trawls and some inventive fun and games. Chief amongst these games was the charity head-shaving which resulted in the raising of some $4,000 for Camp Quality, and some rather unsettling changes to the appearance of quite a few of the local detainees. To the horror of many Bolsheviks aboard, Simon metamorphosed from an ersatz Rasputin into a passable imitation of a trainee bank manager. In contrast, Jason is taking so seriously his transformation from California flower child to goatee-sporting thug that he is to be found lurking belligerently in dark corners of the mess muttering sinister threats to the health of whoever designed the numbering system for the sampling stations. The local deforestation has also added a new, shiny and somewhat spiritual perspective to the morning's stretching classes led by Sensei Warwick "The Rack" Noble. The baldies will hopefully be donning headgear for both thermal and aesthetic purposes tomorrow as we ply the tourist route along the coast – no one wants their iceberg photos ruined by unpalatable foreground glare.