December 22, 2016
As part of the international GEOTRACES program Gila Merschel (PhD, Geosciences), Korinna Kunde (BSc, ESS) and Rebecca Zitoun (Guest scientist from Neuseeland) are cruising the Southern Atlantic at the moment. This is how they experience the voyage.
„After 24h of travelling from Germany and round about 50h from New Zealand, a 6h drive through the Namibian desert was waiting for us. A short tour through Windhoek was followed by an endlessly straight road passing by Uranium mines, farms and monkeys. Upon arrival in Walvis Bay on the coast, we spent the first night in a hotel close to the harbour. The next morning we were picked up and brought to our temporary home, the lovely RV Meteor. 17m in width and 98m in length, the ship gives enough space to 28 scientists and 30 crew members.
The first transect led us from 22°S northwards along the coast through the Benguela upwelling, where nutrient rich waters from below replace the surface waters and make enhanced bioproductivity possible. No wonder, we saw seals, whales, sharks, loads and loads of squids and fish of all shapes and colours along the way. The flying fish probably gained the greatest attention. Further north, we entered the input region of the Congo River. Within a few hours only, the colour of the sea changed from a clear dark blue, to a dirty brown caused by terrestrial substances, the so called humic and fulvic acids, which are transported offshore.
The Congo region provides enormous amounts of nutrients to the ocean. Along with them, there are also trace metals intruding the ocean, which we are especially interested in. The GEOTRACES project attempts to assess the distributions and cycles of mainly Iron (Fe), Aluminum (Al), Cadmium (Cd), Lead (Pb), Copper (Cu), while our working group specializes additionally on the redox speciation of Molybdenum (Mo), Vanadium (V), Chromium (Cr) and Manganese (Mn) as well as the distributions of Hafnium (Hf), Tungsten, also known as Wolfram (W), Nobium (Nb), Ta (tantalum), Titanium (Ti) and Zirconium (Zr).
Since these metals are present in seawater at very low concentrations, we use a special sampling system, the so-called trace metal-clean CTD. Once the trace metal-clean CTD with water sampling rosette comes back on deck, the bottles are brought inside a clean lab container to protect the samples from contamination. Inside, we have to wear white overalls, hair nets and special shoes. Only then we are allowed to start the filtration and fill the seawater into many 100ml-bottles for the different working groups. Back in our lab, we filter the seawater once more through an even smaller filter of only 0.015 µm. This is necessary to separate the truly dissolved trace metals from those that are attached to very small particles, only a few nanometers in size.
As an example, for Vanadium, we process the samples under a nitrogen atmosphere in a glove bag to keep oxygen out. Inside, we conduct a solid phase extraction to separate different redox species from each other, which reflect the varying oxygen concentrations in the water. After each run the equipment has to undergo intense cleaning procedures to avoid any interference between the samples. Therefore, more than one station per day, with up to 24 individual samples from different water depths, is pretty tough in regard to workload and time, so during this part of the cruise we were barely able to sleep and it happened regularly that we spent all night in the lab.
In order to bring the different aspects of the research onboard together, we hold regular seminars in the conference room where the various groups give short talks about their research. Yesterday, for example, a group from Bremen’s Max Planck Institute for Marine Microbiology gave us insight into the secrets of the marine nitrogen cycle.
We continued our transect close to the shore until we reached 3°S where we left the coastal area and followed an east-west transect until reaching the 0°-meridian. The stations here were further apart, so that apart from working in the lab we also got to spend some free time on the ship. We organized movie nights in the conference rooms, read books in the comfy chairs of the ship library and went to the beach.
To the beach? Well, the top deck is equipped with sun chairs and hammocks, and when you lie at 25°C in the equator sun and hear the waves breaking at the ship hull, you just have to close your eyes and you are at the beach. This is probably the most popular place onboard. Second place goes to the bar on one of the lower decks, where red leather chairs, a large TV, games and drinks attract the scientists in the evenings.
By now, we have turned south and we are steaming along the 0°-meridian towards 30°S. Along this transect we are sampling the seawater background for trace metals to be able to compare the different regions with each other. We also have a better time schedule by now because the stations always fall into the daytime and we do not have to work at night anymore. This was also in favor of our Bergfest, a halfway-party some nights ago. We put tables and chairs outside on the main deck, the cook and the stewards prepared a wonderful BBQ with self-caught fish, the captain and the chief electrician performed songs from the 70s and 80s and after sunset, crew and scientists danced into the night.
The party gave new energy to all of us and now we are eager to continue working. While writing this, we are sitting in the lab waiting for the CTD to come back up on deck. We are at around 6km water depth so that deploying the instrument all the way to the seafloor and bringing it back up takes three to four hours every time – enough time to think about Christmas preparations. The crew is practicing Rudolph the Red-nosed Reindeer, Lab No.6 is inviting everyone for the “Christmas Movie of the Day” and Santa’s workshop has opened on the main deck. With the limited material onboard, it needs some creative minds to decorate the ship, but the crew’s ship paint, the electrician’s red tape and some green nail polish saved it.
We are meeting so many inspiring people here, hearing funny and scary “Seemannsgarn” and next to all the work we are simply having a great time here!
Merry Christmas to you all from onboard the RV Meteor!
Gila, Bex and Koko.