Logbook SO306

During the transit to our first working area, all the different teams use the time to set up their equipment and gears. We are doing the same, preparing our aquaria for feeding experiments with cold-water corals, which hopefully arrive on deck in the bio box of the Remotely Operated Vehicle (ROV) SQUID. The crew have already set the room temperature for our cold lab, we mounted the aquaria and the chillers to keep the water inside cool for our corals… almost ready to go!

However, even after many years of participating in research expeditions, there is always a piece of equipment that gets forgotten in a drawer in the home lab… brrr… the good news is that on board there is ALWAYS a solution for everything!

This happened to us yesterday! When we were ready to screw the inlets and outlets of the chillers we realized the needed connectors were missing… arghhh… how could this happen??!!

Most people would expect to see scientists on a research cruise, but a scientific expedition would be absolutely impossible without the crew and the technical staff! They are just as important as the scientists. And the good thing with this expedition is that we have the perfect combination of skills and expertise on board! So… in search of a solution, we visited Tom, one of the technicians from the ROV team, as we thought the team may have spare parts that we could use to fix our problem. But, even better, Tom was able to make exactly the parts we needed using a 3D printer!

It is great to have such fantastic teams on board, always ready to work together!

Now we are ready for the first live coral samples!

Many greetings from the Indian Ocean!

Andrea & Cova

For the days we are working around the island of Mayotte, we were asked to monitor marine mammals and sea turtles in the region. So, we set up a shift plan with always having two persons in the observation room looking around in two-hour shifts from sunrise to sunset. This observation room is high up at the vessel, even above the bridge. But the long way up through several staircases is worth all the effort: the view from this place is simply magnificent!

Well, the MARUM box corer is not really new, but what is new is the video camera that is installed on it. When we investigated cold-water corals during earlier cruises, we always missed the possibility to make a targeted sampling with the box corer at the seabed. Often, we missed the good sample just 2 m away from the point the box corer reached the seabed – but when sampling with the box corer we were literally blind.

Now, these days, it seems pretty straightforward to install camera systems on all kinds of devices. So, the idea of having a camera on the box corer was obvious – from a scientist’s point of view. However, a box corer is a tricky thing and putting a camera system on it, developed to a real challenge for our technicians.

Once in the calm waters around Mayotte, R/V SONNE sailed counter-clockwise around the island’s extensive barrier reef, stopping in the south-west of the island for the first dive with the Remotely Operated Vehicle (ROV). MARUM-SQUID, our ROV, is an unmanned diving robot that is controlled by the ROV pilots from a laboratory onboard. It is equipped with a variety of cameras and sampling tools and can dive down to depths of 2,000 meters!

At breakfast shortly before the first dive, you could really feel the excitement and anticipation of all participants. The plan was to first dive down to a canyon-like seascape at around 950 meters, which had probably been created by a submarine landslide, and then dive up a steep cliff to a flat plateau.

After a few days on board, we start to familiarise ourselves with each other and learn a lot about what the different groups are doing. This expedition is not only multidisciplinary in character combining the disciplines of geology, biology and oceanography, but also very international as our research team includes scientists and technicians from various African and European countries: (in alphabetical order) France, Germany, Italy, Mozambique, the Netherlands, Russia, South Africa, Spain, Switzerland, and Tanzania.

It began with a full beard, which was trimmed into a moustache. A second one followed... And then the social dynamics so typical of a research vessel with many different groups on board set in. Suddenly, more and more people wanted to join in: full beards were trimmed, new moustaches grew...

The 69 members of the nautical and scientific crew included a considerable number of motivated ‘sea bears’ for this special ritual. One of the reasons for this willingness is that there is a good chance that (almost) all traces of this ritual will have disappeared by the end of the expedition - if desired. For now, the more or less successful moustaches are a source of smiles when people meet in the ship's narrow corridors.

Obviously, the CoWIO expedition offers not only scientific challenges, but also a very special social environment that characterises life on board the research vessel SONNE. In the midst of ROV operations, water column measurements and seabed sampling, socialising is an important part for the success of such a research mission. And the urge to grow a moustache, which can be observed in all groups, is a good indication that cooperation on the R/V SONNE works extremely well.

Greetings from aboard the SONNE,

the sea bears (Malte, Finn, Tom, Guillem, Leo, André, Nico, Luis, Vincent, Fabian)

The waters off Tanzania were to be our first working area with cold-water coral mounds. Such mounds consist of a mixture of sediments and coral fragments and allow us to trace the history of cold-water coral ecosystems back in time. We knew there were mounds here that looked like possible coral mounds, and there were corals. But then our initial data showed that the Tanzanian mounds we had detected in old survey data were landslide masses formed during a submarine landslide. Corals do grow on them, but unfortunately, we cannot use them to reconstruct the history of coral colonisation.

So, we kept looking ... And indeed, a night-time survey with the multibeam echosounder revealed a completely different kind of mound structure: 600 meters in diameter, 80 meters (!) high and at a water depth of app. 900 meters, which fits in well with the corals. What is this structure? There has been much speculation: is it also a slide mass? Or a ‘real’ coral mound? It could also be a mixture ... The excitement grew and everyone could hardly wait for the ROV MARUM-SQUID to show the first images from the seabed...

The minds of the ocean science experts onboard the SONNE are true walking encyclopaedias of knowledge, yet, there still is a living child brimming with curiosity in these minds. But let's keep that between us!

From the kids who once played with sand and mud on the playground to those scientists, who keep snails and worms as pets in carefully constructed glass tanks, these senior researchers, who have dedicated most of their lives to uncovering the secrets of deep-sea corals, are simply reliving their childhood passions. From where I stand, there's no better place to see this come to life than in the western Indian Ocean.

What started as a rough sketch for a research project has now come to life in vivid detail on this expedition, revealing the untold story of this lesser-explored part of the ocean. With multibeam maps capturing the seabed in unprecedented resolution and intriguing anomalies that beg for closer inspection with an ROV dive, the narrative of this ocean region is unfolding in thrilling ways.

Today's discovery dive brought both the teachers and students to the same level of excitement and curiosity. What began as a simple exploration of a boulder-strewn seafloor quickly transitioned to the discovery of large beds of bivalves, dotted with patches of colourful corals that were occasionally visited by deep-sea fish. Safely seated in the conference room onboard the SONNE, we virtually accompanied the ROV on its "hike" up steep rocky outcrops, uncovering more bivalves and even microbial mats along the way. During this multi-hour dive, it was impossible to miss the unique exchange of knowledge and the shared astonishment on everyone’s face as we collectively uncovered the secrets of the deep.

So far, no one has written about our hydroacoustic laboratory. Now that the SONNE is on a two-days transit to our next working area on the continental margin of Mozambique, we can rest a little and plan our investigations in this new area. I thought it would be a good time to tell you about our work.

Do you know what ‘hydroacoustics’ actually means? In Greek language ‘hydro’ means water, and ‘acoustic’ is ‘for hearing’. This means, that in our lab we study how the sound waves propagate through the water column. We use a multibeam echosounder system (MBES) that gives us information about the distance (travel time of a sound wave) between the sea surface and the seabed (water depth) and thus about the seafloor morphology. Working with another frequency allowing sound waves even to penetrate into the seabed, the Parasound sub-bottom profiling system provides also data about the structure of the sediments beneath the seafloor.

Seafloor mapping is the first thing we do when a ship comes to a new working area, because without a good high-resolution seafloor map we cannot find coral mounds and other interesting seabed features like submarine channels and mud volcanoes. Soon after mapping, the mapping team consisting of Evgenia, Alissa and Gregor discusses the features they have found during the survey. Based on this information, the chief scientist Dierk plans the locations for subsequent ROV dives, lander deployments and sediment sampling.

Hydroacoustics can also be used to measure the velocity and direction of currents in the water column by using an ADCP (a device for measuring currents based on the Doppler effect), which is my task here on board. The water column is usually not homogeneous, there are different water masses with different current velocities and directions. This is important information for science, but also for the planning of the work during our expedition. For example, the ROV dive can only take place if current velocities are below 2 knots, otherwise the deployment of the ROV becomes too risky.

The people, who do the mapping, often have to work night shifts, because that’s the usual time for mapping as many of the other devices can only be deployed and handled during day time. And for this reason, the members of the hydroacoustic team often have less chance to exchange with the other people onboard and a more irregular sleep rhythm.

Nadezhda

Although this is an expedition that mainly focusses on sessile animals like corals and sponges, we have encountered so many more creatures during our ROV dives, just by coincidence. While the sessile species depend on food being delivered to them through ocean currents, this blogpost is about creatures that swim, float, crawl or walk – some more graceful than others:

In some shared apartments, you can immediately tell who the subtenant is. With corals, however, it is often not so easy. Many of their roommates are tiny and hide well. To discover them, we have to look very closely - and that starts with collecting the corals, which is a particular challenge in the deep sea.

How do we collect deep-sea corals?

As we are in the deep sea, we need special equipment to collect corals. The most important tool is the "Remotely Operated Vehicle" (ROV) - a remote-controlled underwater robot. This robot not only provides us with live images from the depths, but can also "pick" corals with a manipulator.

Before a coral is collected, we first document the entire colony and the individual polyps in detail with photos. The coral is then placed in a waterproof and lockable box to prevent the small tenants from being washed out during the ascent of the ROV to the sea surface. Ideally, we collect several corals during one dive so that later we can compare them.

Congratulations! On 2 September, the remotely operated vehicle ROV MARUM-SQUID completed its 100th dive. The target was the summit area of a seamount at a water depth of 360 metres off the coast of Mozambique (26°S). And just as we had ordered for this special occasion, a beautiful and colourful scene awaited us when we reached the seabed. The summit area was densely populated with the bright yellow cold-water coral Eguchipsammia sp., red and orange soft corals, white sponges and a large dark red sea urchin. A real coral garden, the likes of which we have rarely seen. At the end of the dive, a marker was placed on the seabed with the SQUID to mark that this as the 100th dive with the SQUID during the SONNE expedition SO306 CoWIO.

“Safely secure and tie down all equipment in labs,” were the words that caught everyone’s attention as the announcement echoed throughout the ship. This marked the beginning of our journey to our final operational area—South Africa. A storm was forecasted, but there was another exciting element at play, something well-known to those familiar with these waters: the famous Agulhas Current!

The Agulhas Current is one of the fastest ocean currents in the world, traveling at an average speed of 4 to 5 knots (or 7 to 9 kilometres per hour). To help you picture it, imagine being on the fastest roller coaster ever built, hurtling down a steep drop with the wind screaming past your ears. That’s what the Agulhas Current feels like—but for those living in the ocean!

Our operational area lies adjacent to a narrow continental shelf, which actually causes the Agulhas Current to accelerate. When water flows into a tight space, it’s forced to accelerate, just like how a river rushes faster through a narrow canyon. The underwater topography—complete with submarine canyons and steep cliffs dropping off beyond the continental shelf—acts like nature’s turbo booster, further increasing the current's speed. In contrast, when the current flows over broader, open areas, the water can spread out, slowing down.

This acceleration plays a key role in driving the global thermochaline circulation, which regulates the Earth’s climate by transporting warm, salty water from the equator to the poles. These seawater movements, including other major ocean currents, such as e.g., the Gulf Stream, are crucial for distributing heat and nutrients around the planet. So in essence, the Agulhas Current acts as a powerful force in the global ocean circulation system.

But the Agulhas isn’t alone. Nearby eddies and smaller currents, coupled with the unpredictable weather, add layers of complexity to navigating this region. These currents can create swirling vortices, sometimes trapping marine life or alter the paths of ships.

As we approach the next phase of our mission, the excitement builds. We’re not just venturing into an operational zone—we’re about to experience one of nature’s fastest, most powerful oceanic forces, the Agulhas Current, where even the sea itself seems to race ahead.

Zoleka, Jacek, Nadezhda

If you have never been on a research vessel before, you may be wondering how we dine on the RV Sonne. After all, without our two chefs and the stewards, this expedition would not be possible. Therefore, this blog post is dedicated to them and how everything works around the kitchen.

The same routine day after day, sometimes interrupted by a transit day without station work. So, the days flew by - and suddenly the expedition is over. Arriving in Durban proved to be somewhat difficult, as the weather conditions meant that the helicopter flights taking the pilot to the vessel had to be aborted again and again. At some point, we finally reached the harbour, the first group of scientists was taken to the airport and those who remained on board for the final clean-up work went ashore in the evening. However, we were not greeted very warmly by Durban with a temperature of 14°C and rain.

On Tuesday, 10 September, the last embarked scientists left the SONNE and went to the airport – not without first passing through the immigration office. From there, they travelled in a variety of directions, to northern Germany of course, but also to Tanzania, Mozambique, Spain, the Netherlands and the USA. The many contacts that already existed between the expedition participants before the expedition have now been joined by many new ones, which will be of great importance in the coming years for analysing all the data and samples that we have collected. We are all already looking forward to that!