A tugboat maneuvering the RV Sonne into the harbor of Cape Town after four weeks of transit from Emden. Due to COVID-19, we were not allowed to leave the ship, not even for a jog in the harbor.

Germany’s largest research vessel – the RV Sonne – recently returned to harbor in the port town of Emden after 73 days, the longest-ever research cruise in the history of the ship. I was lucky enough to participate in the journey, which took us to through Cape Town, Walvis Bay and Las Palmas. As part of a team of 30 scientists, 22 women and 8 men, we set out to study one of the most productive ecosystems in the world: the Benguela Upwelling System off the coast of South Africa and Namibia.

Spending this long at sea is a truly special experience and here’s my personal account of what it’s like day-to-day on one of the largest research ships in the world.

The motivation for the trip was the study of Eastern Boundary Upwelling systems – a marine phenomenon that occurs in both the Atlantic and Pacific Oceans, where trade winds push the surface layer of the ocean towards the West. This causes the colder water from the deep sea to replace the surface water.

With the cold water comes the nutrients and oxygen that are dissolved in it, and this leads to algal blooms and the basis for a rich, diverse ecosystem. We encountered lots of charismatic megafauna such as breaching humpback whales, seals, and dolphins, but what really enticed us was the smaller animals we caught in our nets. 

My research group – four women, two master’s and two PhD students – was focused on mesopelagic fishes, fishes that live between 200 and 1000 m (650 and 3300 feet) in the world oceans, most of which undergo a daily migration into the shallower waters at night to feed. 

While I had seen dead deep-sea fishes in museum collections before, catching them in real-time on a ship (floating above a 5000 meter deep abyss, no less) was a completely new experience. Some, for example viperfishes, have a slimy gelatinous layer surrounding their body – likely a way to stay buoyant – that makes them difficult to pick up. Others have deciduous scales that fall off when they feel threatened, so they are effectively scaleless when they reach the surface. Every fish is something special; we even caught some tiny anglerfishes that had swallowed so much food in the net, you could see their bellies extending to the max.

The Research

While in the working area, the ship is constantly on the move from station to station along a predetermined latitudinal transect. The first piece of equipment that goes in the water at a new site is usually a CTD, a device that can take water samples, but also measures conductivity (which can tell us what the salinity is), temperature, depth, and some other oceanographic parameters. This is important baseline information for all the other research that goes on at a specific station. 

After the CTD, the different working groups are able to deploy their equipment – from handheld nets and fishing rods, to large nets, and, on this particular cruise, even a catamaran, a device to catch organisms that live in association with the ocean surface.

The net used to catch mesopelagic fishes on this cruise is an RMT, a rectangular midwater trawl, with a large opening leading to a small cod end where the catch can be removed quickly. While it seems very simple to lower a net to 500 meters, I was surprised how difficult and complicated it really is – from putting the net together, to figuring out how fast to tow it, to then having to change plans when a huge jelly fish bloom clogs your nets for a whole night! Scientists and crew have to work closely together to ensure a smooth and safe deployment and recovery of the net, and new challenges with the net arise almost every night.

However, it’s not just on the technical side that things are constantly changing and evolving, it also happens on the scientific side is as well. At every station, there was something special in the net – from a vampire squid, to hundreds of fishes, to no fish but thousands of jellyfishes – we saw a multitude of different environmental conditions and the changing fauna with it. 

Especially interesting is the echogram, which is constantly being produced while the ship is running the transects. At night, the echogram makes it possible to see the huge masses of migrating animals up into the shallower waters – the largest regular migration on earth. This so-called deep scattering layer shows us in real time how millions of crustaceans, fishes and cephalopods swim up to feed – we can even target individual swarms of fishes with our nets.

During this cruise, we were also lucky to have wildlife photographer Solvin Zankl on board. Solvin’s experience with deep-sea animals made the trip even more worthwhile. His enthusiasm for even the smallest of organisms is infectious and his dedication to spend hours with each animal to capture its beauty as naturally as possible is awe-inspiring.

Life on Board

Life on a research vessel is a lot more normal than you’d expect – with many perks and some downsides. For instance, the convenience of never having to cook or do the dishes for ten weeks is extremely nice. Also, there is seemingly unlimited Nutella on board, a convenience that usually leads to an excess of late-night Nutella bread meetups. There is also a store with chocolate, chips, toiletries, soda, beer, and t-shirts. However, even given such supplies, the stewards did not anticipate the appetite of 22 women for chocolate, and the best kind was sold out after only a few weeks.

Incredibly, the refrigeration on the ship is so well thought-out and efficient that we had fresh salad every day except for the three days prior to arrival in Cape Town – at every other harbor stop, we got fresh tomatoes, cucumbers, and lettuce. Breakfast was usually the highlight of our days at 7am after working the night shift. We even got fresh guavas from Cape Town, a fruit few of us had had before. In general, the food was delicious and very German: lots of Schnitzel, potatoes, and even some Bavarian Weißwurst und Brezen!

One downside is that if you get seasick – and I do – the waves and weather forecast can mean the difference between a relaxing day and a day spent in bed trying not to throw up. Thankfully, we had a meteorologist on board who brought good luck with her; the waves never exceeded four meters in height throughout the whole cruise.

Cruising during COVID-19

Normally, the scientists on board are very international and fly in from all over the world for the unique opportunity to sample the oceans on such a high-tech vessel. The FS Sonne has been to harbors all over the globe in the last 7 years since its inauguration. However, due to Covid-19, all cruises start and end in Germany. Unfortunately, with travel restrictions, this meant that only few international scientists could join this cruise. In addition, scientists who were not fully vaccinated yet had to endure a ten-day quarantine in a hotel room. Upon arrival on the ship, we tested ourselves every day, concluding in a PCR test by the ship’s doctor, after which we were able to go mask-free for the remainder of the cruise.

While it is certainly not all rainbows and butterflies every day on a ship, it is an amazing, life-changing opportunity to see and experience things few humans have ever seen or experienced before. I’m happy I was able to participate in this cruise, and also to have met 29 other researchers crazy enough to leave solid ground for 73 days for their love of science.

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Eva Paulus has been on five research cruises so far, but this was the first time she got to be part of the field research sampling deep-sea fishes. Follow her on Twitter @Deep_Sea_Dirndl. You can also check out Solvin Zankl’s wildlife photography on his website or on Instagram.