Text and photos: Mauro Pau
A fun moment during the working on the just acquired core.
Here are some personal impressions from cruise CAGE21-4 to the central Barents Sea. Let’s start with the negatives. Unless this cruise was sponsored by a known milk brand, there is no excuse UiT cannot provide decent quality drinking water to its employees. A few of those big water jugs can only be beneficial for future cruises on R/V Helmer Hanssen.
Sediment for headspace gas analysis is sampled from the freshly exposed base of a core section.
Apart from that, what a valuable experience it has been. I enjoyed the hands-on working, for instance when collecting sediment samples for headspace gas analysis, which I had never done before. I am also glad for the practice gained at multibeam water column image interpretation while picking gas flares (altogether we identified over ten thousand flares).
Henry brings a core section into the lab.
Preparation of the core for storage.
This cruise has been filled with many moments of awe. On one occasion, I was drawing porewater into vials containing mercury chloride (the most toxic chemical I have ever used), and saw them turning each a different shade of yellow, reflecting increasing sulphide concentration downcore. Sulphide is a product of the aerobic oxidation of methane in the sediments, so just by looking at the colour of the vials one can infer that there is a strong methane flux in that environment.
Porewater is collected from cores using rhizon samplers, polymer tubes inserted into the sediment and fitted to low-pressurised syringes.
Mercury chloride is an extremely toxic chemical, and we add it to stop microbial activity in porewater samples. Incidentally, it reacts with sulphide ions forming mercury sulphide, a solid precipitation of yellow colour. The darker the yellow, the higher concentration of sulphide.
We spotted several whales and dolphins along our way. One memorable scene was when an oil sampling trip on the dinghy boat turned into a whale safari. A finback whale at least three times the size of the boat materialised out of the blue. We were struck by her sound; the photo does not do justice to how amazing it was to be there.
A finback whale pays us a visit and inquires about our research.
Fishcakes and porridge for breakfast has been yet another experience, most likely a unique one, though I’m glad I can now brag about it.