to the Benguela Current

Expedition

SONNE, sea blog of the 285th cruise

The research vessel SONNE at the port in Emden, Germany (© Solvin Zankl)

Duration: August 20th to approx. November 2nd, 2021

Area: Benguela Current in the South Atlantic

Purpose: Investigations within the project TRAFFIC

Scientist in charge: PD Dr. Tim Rixen, Leibniz Centre for Tropical Marine Research (ZMT)

Objectives

Planned route. Red dots: Stations on the way to the destination area. Black dots: Stations in the northern and southern Benguela upwelling area. (© ZMT)

Off the coasts of Namibia and South Africa lies the Benguela Upwelling System, one of the most productive and fish-rich regions of the Atlantic Ocean. In the 1970s, however, fishing yields of sardines, which had been caught predominantly until then, declined. With climate change, other fish species and also jellyfish moved into the region.

The research expedition aims to find answers to the question of how climate change affects the marine ecosystem off South Africa and Namibia and its services with regards to fisheries and ocean CO2 storage. As climate change is gaining momentum and the ocean is relatively slow to respond to it, the research on the RV SONNE is integrated into various long-term observation strategies. These are primarily initiatives of the partner institutions in Namibia and South Africa, but also international programmes.

The task of the researchers on board is to decipher processes that help to clarify how the circulation of the ocean under the influence of regional coastal morphology affects the productivity of the marine ecosystem as well as its capacity to store CO2. Understanding such processes is essential to improve predictions and adapt guidelines for the use of marine ecosystems to global change and thus contribute to food security and climate protection.

The cruise is part of the research project TRAFFIC („Trophic Transfer Efficiency in the Benguela Current“), joined by five German and five Namibian and South African research institutes. It is coordinated by the Leibniz Centre for Tropical Marine Research (ZMT) and funded by the Federal Ministry of Education and Research (BMBF). On this cruise, a scientist of the Thünen Institute of Sea Fisheries, Sabrina Duncan, is on board.

Project flyer

Barbara Springer reports:

After 27 days at sea, we reached the port of Cape Town on the morning of September 16th. The city is located in the southwest of the Republic of South Africa and is known for its landmark, the Table Mountain. Entering a port is always something special, especially when you've spent weeks at sea without seeing land.

Usually there is a lot of activity on a day in port because the port call must be planned intensively by the captain in cooperation with the chief scientist, the ship's agent in the port, the shipping company and other agencies: When will the provisions be delivered? How much rubbish is to be disposed? And when to bunker the fuel?

Due to the strict Corona regulations in South Africa, everything was a little different this time: The ship waited in the early morning in the roadstead for a boat with medical staff, who tested both the crew and the scientists with a rapid test for the Corona virus. Only after it was clear that all tests were negative and the pilot boat arrived. With his help and two tug boats, the SONNE was brought to the pier in Cape Town and moored.

Then the agent and the authorities came on board to finish many formalities. We scientists stayed away for safety reasons and watched what was happening from the higher decks. Due to Covid regulations, we were not allowed to leave the ship, but we certainly enjoyed the view of Table Mountain!

The supplies for the galley were also replenished: fresh vegetables, lettuce and fruit. In addition, 14 canisters (5l each) with dishwashing detergent were delivered.

The food and the quality of the catering contribute significantly to the good mood on board. At the moment, two cooks cater to the 62 people at the SONNE every day. The meals are always rich, varied and very tasty. Maybe a few figures: 60 rolls and 2 baguettes or breads are baked every day, around 130 eggs and almost 2 kg of butter are used, 1 kg of coffee is consumed, as well as 12 liters of milk. There is also mineral water and juices. The storage rooms and storerooms have to be filled accordingly.

Kudos to the chefs for the delicious meals and to the stewards for the excellent service around the clock! We have to be very careful not to come home with too many added pounds, with all the great meals!

After 14 hours in port we headed to our first sampling stations! More about that later in our next blog entry.

5th Weekly Report (PDF) of chief scientist PD Dr. Tim Rixen (Sep. 13 - 19, 2021)

Luisa Meiritz reports:

PIRATA buoys in the ocean – no, we don’t talk about pirates, but about a data collecting project. PIRATA stands for ‘Prediction and Research Moored Array in the Tropical Atlantic’ which is an anchored measurement system for forecasting and research in the tropical Atlantic. These buoys are weather buoys that are firmly anchored to the seabed and transmit information about the weather and surface water masses via satellite to land around the clock. Parameters such as solar radiation, wind speed, water temperature and water currents are measured with different sensors above and below water.

The PIRATA project has been around since the 1990s and has been expanded and developed since the 2000s in order to collect weather data, especially in the tropical Atlantic. Several tropical Atlantic bordering countries are involved in this project under the direction of NOAA (National Oceanic and Atmospheric Administration).

For a previously unknown reason, two PIRATA buoys broke loose at the beginning of 2021 and are now drifting freely in the ocean. And this is where we come in. The vessel SONNE is currently the only research vessel that is in the vicinity of the free-floating buoys. Therefore we try to salvage the buoys and bring them back home safely!

4th Weekly Report (PDF) of chief scientist PD Dr. Tim Rixen (Sep. 6 - 12, 2021)

3rd Weekly Report (PDF) of chief scientist PD Dr. Tim Rixen (Aug. 30 - Sep. 5, 2021)

Report of the Biogeochemistry team:

One of the aims of the TRAFFIC research project is to get to the bottom of the effects of climate change on the ocean's CO2 storage in the Benguela upwelling region. Onboard the RV Sonne, the biogeochemistry working group is now particularly concerned with understanding and quantifying the circulation and turnover of carbon in the water column, as well as the gas exchange of CO2 at the ocean surface with the atmosphere. Following up on our previous research cruise on RV Meteor, we will address the influence of the different source water masses feeding the northern and southern upwelling systems to different extents, and investigate seasonal characteristics, e.g., with respect to oxygen and nutrient concentrations.

Our research methods include sampling the water surface using measuring systems that are continuously supplied with seawater pumped from the ship's moon pool from a depth of about 5 meters. Together with the atmospheric concentration, we can thus determine the parameters relevant to us. These include pH, surface temperature and salinity, partial pressure of CO2, as well as alkalinity and dissolved inorganic carbon concentration.

To study the water column, water samples are collected from the CTD rosette's crown water sampler to analyze the supply and turnover of nutrients, which contribute essentially to the productivity of the marine ecosystem. Furthermore, mooring systems are used to collect short- and long-term particle transport from the ocean surface to the deep water layers via so-called sediment traps. This can then be evaluated biologically and geochemically.

The team of our working group Biogeochemistry consists of the students and the research assistant from the University of Hamburg, Natalie Reule, Sina Pinter and Luisa Meiritz, our technician Fabian Hüge from the ZMT, as well as the two PhD students Sina Wallschuss and Claire Siddiqui from the University of Cape Town and University of Hamburg/ZMT.

So far, we have been able to test many of our instruments. We are very much looking forward to the upcoming work and are eager to see the results we will gain on our second TRAFFIC cruise.

Many greetings from aboard the RV Sonne,
the Biogeochemistry Team

2nd Weekly Report (PDF) of chief scientist PD Dr. Tim Rixen (Aug. 23 - 29, 2021)

On August 20th the scientists of the TRAFFIC project set sail on the R/V Sonne 285 expedition. Due to Covid regulations in international ports, this trip is a little longer than the last. Instead of flying to Walvis Bay, Namibia, as on the first expedition in 2019 (Meteor 153 cruise), this cruise begins in Emden, Germany and will sail to the Benguela Current, and then return back to Emden in November for a total of 74 days at sea.

On the cruise there are thirty-two crew members and thirty scientists. Many students are looking forward to their first experience on a research vessel. All, scientists and crew must wear masks, take a daily rapid self-test, and on the 7th day will have a PCR test before the sense of normalcy can begin.

The aim of the TRAFFIC project is to investigate carbon uptake and the efficiency of the food chain from phytoplankton to mesopelagic fishes in the northern and southern subsystems of the Benguela (for details, see link to TRAFFIC project above).

After leaving Emden, the unloading of gear from containers began. This was followed by the set-up of laboratories and equipment such as the CTD, zooplankton multinets, and fishing nets. To take advantage of the long journey, the team will not only be sampling in the Benguela region, but they will also have stations along a transect, starting with a station located in the open ocean, off the Bay of Biscay. At the first station, the CTD Rosette will be deployed to collect the first water samples and a multinet will be used to collect phytoplankton and microzooplankton at various depths in the water column. During the next days, new and old gear will be tested, such as a fishing net which is a combination of a Rectangular midwater trawl (RMT 8), and a connected multisampling net.

On the morning of August 22, the group witnessed their first of hopefully many dolphins to come and is eager for what’s next!

Cheers,
The TRAFFIC Team

1st Weekly Report (PDF) of chief scientist PD Dr. Tim Rixen (Aug. 20 - 22, 2021)