By Jasmin Heiden, Florian Koch et al.
On March 2nd it was our (the biologists) big sampling day. We sampled seawater from 25 m depth at a site in the Drake Passage. During this cruise we will sample three stations where we pump water on board in order to conduct incubation experiments with the in situ phytoplankton community. Yet, our sampling is not as easy as it sounds.
On the morning of March 1st ,one day earlier than expected, we were informed that after lunch we would be arriving at our biology station 1.. Every one of us was excited and we finalizized our preparations and were eagerly standing on deck ready to lower our sampling tube. Our rather simplistic sampling array consists of several plastic weights and PE (polyethylene, a specific kind of plastic) tubing, attached to a rope which we lower to 25 m depth using a dyneema winch. Under optimal conditions the tubing hangs vertically. However on this day the wind was blowing strongly and the waves were appox. 4.5 m high with strong surface currents and as a result our tubing ended up at a very obtuse angle with the end most likely not at 25 m depth, but instead at the surface. This is problematic, because we require the low iron and other trace metal seawater for our experiments and since the Polarstern, like most ships is made out of metal and draws 11 m sampling water at insufficient depths would likely result in metal-contaminated seawater. After a lot of discussion we had to accept that it was necessary to stop the sampling, bring the sampling line back onboard and wait for better conditions.
As the geologists onboard had a sampling station nearby which they could prepone this gave us several hours during which the wind would die off and the waves got smaller. The plan was to try again 10 h later, as the weather forecaster expected good conditions by then. Finally at 12:30 a.m. our dear friends from the bathymetry group woke us up, because we were already close to our biological station. As we, however, checked the wind and wave conditions, our mood dropped realizing that both hadn’t changed much since our first sampling try a few hour before. After dissing we finally decided that Polarstern will continue travelling south. Everyone of our sampling team went back to bed. To catch some more hours of sleep hoping that meanwhile the winds would calm down. At 5 a.m., our reliable colleagues from the bathymetry woke us up (again) as we were about to arrive at the sampling location further south.
Anxiously we stepped outside to check on the wind state and wave height here, but this time we were lucky. The wheather conditions were finally good and everyone was relieved. We then attached our tubing to the rope and lowered it to 25 m. Then we turned on the pump and with a monotonous klonk-klonk it started its 24 h marathon of pumping seawater up onto the boat and through the tubing into a clean laboratory. In this special super trace metal clean laboratory three of us started to fill plastic bottles with the water including the microalgae pumped onboard while three more persons were waiting outside the lab container in order to locate those bottles inside of cold room containers exposed to various experimental conditions. This transfer to the cold room containers has to happen fast as we do not want the microalgae to get warm as this would stress them. The containers in which we conduct the experiments are cooled to the ocean water temperature (~1 °C). Once all experiment bottles were filled we also took samples from the sampled seawater to characterize its microalgal. Around 4 p.m. and after 11 h hours of continuous work the first shift was finished while the second shift just started their sampling for the next 12 h.
best wishes, the ProIron group