Our cruise is coming to an end and it’s time to reflect on our work – what we have explored and discovered during our journey from the far, cold and stormy North of Iceland, Greenland and the Labrador Sea, to the sunny, warm Southern waters of the sub – tropics!
As on our last cruises, the station work followed the same procedure: Each station starts with a CTD and a multibeam mapping survey, followed by benthic, pelagic, and water surface gear. Keeping a similar schedule is especially important, as the overarching goal is to make assumptions about a potential longitudinal connection (or disconnection) of Atlantic deep-sea species and life. This is a challenging task, as each instrument only samples an extremely small part of the ocean but is expensive – hence stations have to be picked carefully and with good reason for they function as representatives for other, non-sampled regions. I would like to take a look back about our findings – because they were quite a few!
CTD – the fundamentals of research
CTDs measure salinity, temperature, and pressure of the surrounding water. This is an important measure as little changes in one or more of these parameters can heavily alter living conditions and hence local ecosystems. In the CTD profile we took of the Labrador Sea, we found a particular deep-water layer, indicating low salinity, high oxygen, and very cold temperatures. This can be directly related to the fresh water formation that is known to prevail in this spot, just off the coast of Newfoundland. Knowing this in theory is good, but seeing it live is very impressive!
MBES – Welcome Mt. Doom
Fortunately, we were given a lot of time for mapping, revealing so far undiscovered fantastic underwater formations. The clear highlight was an extinct ancient caldera with its two little younger sister volcanoes just off Newfoundland. It is estimated to be 49.5 million years old, but its harsh edges, encircling a perfect half-moon shaped steep crater and a sharp pointy tip might tell different stories to the untrained eye – yet this accounts for the very slow pace of erosion and decay in the deep sea. In honour of the most epic fantasy tales of one of the greatest novelists, we called the grand caldera ‘Mt. Doom’.
During transits between the stations, we crossed over other various unique features. The gentle shape of sandy dykes, formed by the powerful meanders of deep bottom currents, showed up on the abyssal plains between the Canadian continental shelf and the Azores. Towards the Mid Atlantic Ridge, rocky and solid fissures, faults, ridges and trenches, having emerged from the crimping and twitching forces of plate tectonics, became visible on the screens in our multibeam observatory.
Collecting human legacy
The Neuston Catamaran, a gear dragged behind the ship on the water surface, collects anything floating. Our scientist in charge here is Denisse Galarza from GEOMAR (right), she is a biologist and specialist of plastics in the sea. The catamaran is mainly deployed to sample pieces of plastic, and unfortunately, this is exactly what we found in masses – especially much when crossing the garbage patch just south of the Azores. Impossible to spot in the ocean with the bare eye, hardly visible even when collected, plastics has entered the entire life cycle. One of the catamaran samples contained Sargassum – a special type of floating seaweed – which had already been covered with the synthetic material. Small animals populating the Sargassum have already integrated the plastic pieces into their daily habits: Shrimps for example use it as a solid platform to sit on – a phenomenon that can also be observed on the sea floor of the abyssal plains, where hard substrate is rare. Denisse further found microplastics clinging to the sticky tentacles of a medusa. This is a very sad and irretrievable fact and cannot be undone, as plastics eventually decomposes into very small pieces that are unfeasible to collect on a big scale. Although it is an old and meanwhile well-known story, it can’t be said often enough that minimising plastic consumption is an absolute must – whether it is industry, politics, or the private consumer in the supermarket – anyone can contribute here! At this stage, it might be worth mentioning our trash map, where we track litter found during our OFOS dives as well as from the Neuston catamaran. Check it out here: https://experience.arcgis.com/experience/8260b2c831de448ea905fb021cacb313.
Biology – the seen and the unseen
As on our past cruises, the biologists on board found a whole range of species – some of which have even been undiscovered until now. To make them accessible and comparable, each individual needs to be described as detailed as possible before being added to a constantly growing database. Responsible for this on board is Karen Jeskulke (left), she is a technical assistant, at DZMB Senckenberg am Meer. Eventually, for those small species that play such an important role in the ocean life cycle, the more is known about them, the better humans can understand the world and occurrences like climate change and its impacts. Whether we will be fast enough with this knowledge gathering though to make actual changes before it is too late, is questionable. Yet what we have learnt, is that those amazing animals basically can get used to anything. And that there are many ways of how creatures can adapt to, sometimes really hostile, surrounding environment. One of the most obvious phenomena is their outer appearance – figure, size, colour – that changes with respect to their nature.
Whether being hunter or prey, opportunistic feeder, mobile or sessile – there are many reasons to vary the look! Far less visible and known is that deep sea inhabitants may adjust their sex and genders depending on their situation. A vast diversity – and for once, I am not talking about bio-diversity, takes on the most creative and astonishing forms. A large number of deep benthic species consider themselves non-binary – meaning they can be male or female at the same time or switch between the two. More opportunistic souls may decide what they are according to their needs, for example when it is mating time – until then staying rather gender neutral, or agender as for instance deep sea bivalves. Others, like sea horses, laugh at the classic roles by letting the males settle down to carry out the brood. Barnacles on the other hand are gender fluids – male and female simultaneously – having grown extraordinary reproductive organs of considerable size which enables them to procreate across distances. Some individuals can vary in body size depending on local conditions and their significance to others – like that, the frogfish female diva is about 20 times larger than the male, who is nothing more than a sperm carrying sack. He would, if larger, only scavenge even more of the already rare and valuable food. Of course, there are also species of binary sexes, but they are a minority. Hence and again, we can learn from the ocean – embrace diversity, for it is a valuable and very much inspiring!
Captures of the true artists
OFOS!! We love OFOS, the towed underwater camera system. Our person in charge here is Dr. James Taylor (right), a marine biologist from DZMB Senckenberg am Meer. This sort of gear is especially beautiful as it hardly disturbs the deep-sea life, except for a short period of light pollution. Through the camera lens, we have again been offered the most stunning and peculiar captures of submarine habitats in its original state, and I cannot say often enough how exceptional and fascinating this world is. Far away from human impact, it has developed over millions of years and the flora and fauna have adapted to the rough conditions of cold ever darkness. Only rest light of ambient bioluminescence is utilised by the local inhabitants to communicate, hunt, lure, or mate. But, talking about this is obsolete – let the images speak!
