Day 25: July 15 2020
We leave the beautiful vent site behind us and head further south, riding on the storm and through heavy waves again. Time to take a look at what is going on in our onboard laboratories!
When samples are taken – geology or fauna from the ROV dives, EBS, plankton net, MUC, and box corer – they have to be observed and documented. Depending on the sample type, there are various methods to investigate the ‘prey’: sediment is being washed and sieved, water is being filtered to remove ‘pollution’ – larger bits that may misrepresent the actual sample – whereas bigger samples from the ROV or plankton net go directly into the labs to be examined under the microscope. Then comes the sorting. If you have ever wondered why biologists (maybe humans in general) have the tendency to create never-ending lists of various categories: groups, families, sub-families, genus, species and sub species … (to be continued) – here is why: things have to be put somewhere! Following ‘if you have a problem, give it a name’, taxonomy and generating categories are key to communicating about biodiversity and our understanding of how species distribute, behave and function together. This is why biologists sort all samples (in laborious, time-consuming fashion) under the binocular microscopes into groups: to find common features, similarities and differences across the collected species. The most frequent animals they find in the micro- to megafauna are: corals (anthrozoa), sponges (porifera), crustaceans (including decapods, amphipods and isopods), shells, molluscs (bivalvia and gastropoda), and the vast array of worms – the polychaetes. Each of them tells their own story about its habitat and the ecosystem it has been living in, as well as tales about its eating habits and travel patterns. For example, worms prefer soft sediment where they can dig a hole and either filter the water to feed or, in some cases, catch passing smaller animals. A rocky mid-ocean ridge is not a suitable environment for a soft sediment worm – hence it acts like a natural barrier and keeps the worm in place. All of those elements – fauna or ‘dead’ material like sand and stones – are interwoven in highly complex patterns, all interacting and forming unique and vulnerable habitats that react to even the smallest changes. We still have a long way to go and are far away from understanding this multifarious structure, but in very small steps we are getting there.
Depending on the field of interest, the next steps in the sample processing journal are fixing (preserving) the animal in either formol or ethanol, to allow us to investigate its morphology or genetics, respectively. The removal of animals from the seafloor is a very sensitive subject, and we strive to not take more specimens than we need to understand and describe the ecosystem efficiently.
But now for something completely different. It’s …. dark again at night time! After three weeks of 24h sun, which is stunning and beautiful but completely messes up the daily rhythm, a few dark hours are a gratefully-received gift for a much-needed sound sleep!