Beginning the return voyage

Polarstern arrived at Punta Arenas on 8 April from its previous expedition (PS97). Since another ship occupied the intended pier, Polarstern could not berth there. For that reason, the bunkering of fuel was done at Cabo Negro. For one more day, the vessel remained anchored in front of Punta Arenas. Finally, in the morning of 10 April Polarstern berthed at Mardones pier. All cargo handling as well as the embarking of the scientists was finished quite rapidly, so that we could leave Punta Arenas according to the plan (18:00 local time).

After the quick passage of the Magellan Strait (with strong currents from the back) Polarstern made extremely good progress and we are now sailing on the South Atlantic with a northeasterly course. The first days were still influenced by the cold waters of the Falkland current. In this region we also experienced the influence of the southern frontal zone with corresponding winds up to 8 Beaufort and waves of 3 meters height. These conditions were a first successful test for equipment and scientists. Now we already reached the warm waters of the Brazil current with temperatures of around 23°C. We passed also through some thunderstorms caused by a low-pressure trough over the South American continent. Our route will bring us directly to the Canary Islands where our arrival is planned for 3 May.

Thanks to the very helpful crew, life on board is very comfortable. Already in the first week we could enjoy the delicious and abundant food, as well as leisure activities such as gym, indoor pool or table tennis. Thanks to the higher temperatures, we had a barbeque on the working deck yesterday evening.

The scientific work of our cruise has started according the plans. The different research topics will be presented in detail in this and the following weekly reports. The report of the biology group (Corina Peter, Marcel Machnik, Rodrigo Lorenzo):

On Saturday before sailing out of Punta Arenas, Polarstern received special passengers on board. Big Aquaria are already built up on the F Deck in Biolab Containers, cooled down at 5°C. They are filled with seawater of the right temperature and ready to host the crabs. They should feel comfortable on the transport: The unusual passengers are Stone-crabs, commonly also called King Crabs. Two different species of Stone-crabs, Lithodes santolla and Paralomis granulosa, which are common in the area around Punta Arenas, were moved in their aquaria on board. The crabs were caught in the Magellan strait, where water´s temperature is about 5°C and the salinity is around 28 ppm. We boarded in total over 60 Stone-crabs of both species. Once the ovigerous females and the males were separately sorted in their tanks, they were measured, tagged and checked the vital parameters noting everything down. Crabs husbandry includes daily exchange of seawater with fresh seawater, this is done in order to keep its optimal quality and avoid the toxic accumulation of metabolites. As we travel north and approach warmer surface water, the seawater must be cooled down with a cooler tank. In addition, an important parameter to control is salinity, since crabs can tolerate salinities up to 33 ppm but in tropical areas, it can reach up to 39 ppm. The male king crabs are currently encountering their annual molting phase (between March and April) and the females are ovigerous, which is why both are sensible towards too high variability in temperature and salinity.

When arriving in Bremerhaven the animals will be used in different projects; in order to investigate how the animals react in climate change to warmer temperatures and decreasing oxygen availability in the water and furthermore to ocean acidification. Females and their eggs are believed to react especially sensible towards changes. The goal is, amongst others, to examine the brooding behavior of females as well as the development and oxygen consumption of eggs under changing environmental conditions.

On behalf of all cruise participants, best regards

Bernhard Pospichal

17.04.2016, 31°S, 42°W