Logbuch RV Pelagia Dust-2023

Expedition with the R.V. Pelagia to Cap Blanc

The R.V. Pelagia is a Dutch research ship deployed by the Royal Dutch Institute of Sea Research (NIOZ). A Team from the German Science Foundation funded Excellence Cluster “The Ocean Floor – Earth’s Uncharted Interface” RECEIVER and RECORDER Units will join this cruise to the subtropical region southwest of the Cape Verde Islands and the upwelling area off Cape Blanc (NW Africa). The eastern subtropical Atlantic upwelling area off Cap Blanc (NW Africa) is one of the most productive regions in the world. This is due to the high input of nutrients in the upper water column that are upwelled from deeper waters and enter the region in the form of Saharan Dust Input.

The region plays a key role in the global carbon cycle and as such influences the global climate. Particles that have trapped atmospheric CO₂, sink from the upper water column towards the ocean floor and as such form a sink for atmospheric CO₂. These sinking particles are the focus of a long-term monitoring program of the MARUM. In this program the particle production in relationship to climate change are followed since 1988 by collecting the flux of particles sinking through the water column by moored sediment traps.

cruise track of cruise Dust-2023 — Cruise track of cruise "Dust-2023"

At the same position of one of the MARUM sediment trap moorings, the NIOZ deploys a so called "dust-buoy" that collects dust from the atmosphere. This allows us to directly correlate variability in particle export flux with the input of Saharan dust.

Throughout the years a close cooperation exists between the MARUM and the NIOZ and a Dutch team frequently joined MARUM expeditions to the region. This time, a MARUM team is welcome at the R.V. Pelagia to service the MARUM sediment trap moorings and perform investigations in the scope of current activities in the excellence clusters units RECEIVER and RECORDER.

Apart from servicing the sediment trap moorings they will study the particle production in the upper water column, the sinking behavior (transport) through the water column and preservation/degradation at the ocean floor. For this, the particle flux from the upper water column will be sampled with free drifting traps. These traps float with the upper water currents and collect the particle at different water depths. At the same time, temperature, salinity, chlorophyll-a content and turbidity of the water column will be recorded throughout the surveys. Apart from this the particle content of deeper water layers will be collected by so called "in-situ" pumps. Furthermore, ocean floor sediments will be collected to study the long-term changes in the region and investigate to what extent anthropogenic pollution has influenced the ecosystem.

The team of expedition R.V. Pelagia - Dust 2023 will report on the cruise and everyday life on board in an expedition log.

More information:

About the Expedition

Expedition blog from NIOZ

Current position of the research vessel R.V. Pelagia

Contact:
Prof. Dr. Karin Zonneveld
Micropaleontology – Paleoceanography
MARUM – Center for Marine Environmental Sciences, University of Bremen
Phone: +49 421 218 65797
Email: [Bitte aktivieren Sie Javascript]

Friday 03.03.2023; “We’re on our way”

Lissabon.

Today we started our trip a little bit different as initially planned (by car in stead of train/bus) because of the big demonstrations in Hamburg and Bremen today that severely hampered the use of local train/bus and metro connections.

We safely made it on time for our flight to Lisbon where we have to stay for one night to travel further to the Cape Verden where the ship Pelagia is expected to be waiting for us tomorrow.

Before the cruise we needed quite some preparations, not only by sending our research equipment by container to Mindelo already early February, but also in preparing ourselves by absolving a marine life-safety training. There we practiced in the swimming pool of the Dutch town Emmeloord how to behave in case of emergency for instance, how to put on a safety suit as fast as possible and climb in a floating life raft.

Training of a “helicopter saving”. You have to keep your arms stiff alongside to prevent slipping out of the orange sling. Photo: MARUM — Training of a “helicopter saving”. You have to keep your arms stiff alongside to prevent slipping out of the orange sling. Photo: Jan-Berend Stuut

Saturday 04.03.2023; "Arrival in Spring"

Mindelo/Cape Verde.

Today we arrived safely in a nice warm sunny Mindelo (Cape Verde).

The Pelagia had some delay so that made it possible for us to see the ship entering the Port of Mindelo in the late afternoon. It gave us some time to get used to the transfer from cold-gray Germany to the subtropical spring on the Cape Verde. Tomorrow we will go to the ship to get ourself settled and start to unload the equipment from the container and set up our working places.

Arrival at Sao Vicente airport. Photo: Karin Zonneveld

Pelagia sails into the Port of Mindelo. Photo: K.Zonneveld

Monday 06.03.2023; “Parking Jam”

Mindelo/Cape Verde.

Under a beautiful blue sky with a refreshing breeze a busy day started. Today the containers with our equipment arrived and we have to prepare the laboratories for the upcoming cruise. Although this sounds easy, in practice this requires quite some logistic puzzling. This since the arriving containers with equipment of the upcoming “Dust-2023” cruise have to contain all the equipment of the previous cruise on their return way to Europe. So... first the containers have to be emptied with our equipment stored somewhere where it is out of the way, then the equipment of the previous cruise has to be stored in previously emptied container and care has to be taken that every container exactly contains that equipment what is written on its custom papers……. Happily, the MARUM Logistic team members Marco and Götz handle this reality version of the “Parking Jam” game excellently.

Equipment “Parking Jam” on Deck of the R.V. Pelagia. Photo: K. Zonneveld

Group photo in front of the Pelagia. Photo: MARUM

Tuesday 07.03.2023; “On our way”

Leaving the Port of Mindelo. Photo: K. Zonneveld

Between Cape Verde Islands.

Finally in the early evening the Pelagia was ready to sail off. This meant, the fuel had been refilled, new food and water taken in and all the scientific equipment was stored and sealed safely in the laboratories and storage containers. We waved goodbye to the friendly and colorful city of Mindelo and sailed the sunset painted horizon in between the Cape Verde Isles south for our first research station where we hope to arrive at Thursday morning.

Wednesday 08.03.2023; “Testing”

Southern Cape Verde Islands 14.5423 N, 23.8863 W.

Fortunately, the nice weather has followed us from Mindelo and today not only the sky is blue but also the Ocean shows its best side.

Today is a day of testing. We started the day with a safety drill to get ourselves familiar with the fastest way out of the Ship to the assembly point and life rafts to be well prepared in case of emergency. Here we tested if the survival suits everybody got at the start of the cruise were of the right size.

After this we started to test all our scientific equipment to see if nothing got damaged during transport to Mindelo. We successively adapted our equipment to the ships specific characteristics such as the thickness of the wires which are used to deploy devices in the deep ocean.

Not all tests can be done on deck. For instance, the so called “CTD” a device that measures the temperature and conductivity of see water from the surface to just above the ocean floor (on our location 4038 m), only functions when it is in contact with Seawater.

Katell Alaime and Runa Reuter testing the sediment oxygen sensor. Photo: K. Zonneveld

As a result, we stopped near the most southern Cape Verde Islands to run a test CTD and tested if not only the CTD itself but also the additional sensors that measure the oxygen concentration as well as the amount of particles in the water column (turbidity), functioned.

Fortunately, so far all tests were positive providing the best prerequisite for successful deployment of the devices on our first station tomorrow.

The first CTD arrives on Deck. Photo: K. Zonneveld

Thursday 09.03.2023; “Laura” collecting dust

Southeast of the Cape Verde Islands. 11.3592 N, 22.9803 W.

Just after lunch we saw “Laura” as a yellow spot at the horizon of a bright blue ocean. “Laura” is the name of one of the two dust collecting buoys of the Royal Netherlands Institute of Sea research. For part of the MARUM team it was “a welcome back” as she was put to sea at the MARUM Receiver cruise MSM104 in November 2021.

Since then, she has been collecting Sahara Desert dust from the atmosphere. This dust contains a lot of nutrients that fertilizes the ocean stimulating phytoplankton growth. This plankton also takes up CO₂ that has been diffused from the atmosphere into the ocean water. When the plankton dies, it sinks to the ocean floor carrying this CO₂. As such, it is a natural process that removes CO₂ out of the atmosphere to be stored at the ocean floor.

To date, it is however not exactly known how much CO₂ is extracted from the atmosphere when dust is blown into the ocean. To enable the study of this process “Laura” did not only collected dust but was also equipped with many sensors that registered the ocean water temperature, salinity, amount of rainfall and wind speed.

Recovery of the dust Buoy Laure. Photo: K. Zonneveld

After a safe recovery of Laura, the NIOZ research team of Prof. Jan-Berend Stuut immediately started to extract the data from the sensors and servicing the buoy as we plan to put her to sea again tomorrow for another two years of dust and data collecting.

Bob Koster (NIOZ) explains MARUM PhD Runa how to retrieve weather and oceanographic data from the sensors on “Laura”. Photo: K. Zonneveld

Friday 10.03.2023; “Sediment traps”

Southeast of the Cape Verde Islands 11.3592 N, 22.9803 W,

In contrast to the water near the MARUM where winter gives “goodbye snow greetings”, our day started again with a blue ocean and subtropical temperatures. The morning of this Friday was filled with preparing “Laura” for another sampling interval. She got completely new devices that were prepared already at the NIOZ in the Netherlands. Just after Lunch she could be released to the ocean again.

After waving her goodbye we immediately sailed to the position of the nearby sediment trap mooring. Sediment traps are big funnels that collect particles that sink from the ocean surface down to the ocean floor. They are connected on a wire to an anchor at the ocean floor and are kept upright with floating bowls. The whole construction of anchor, wire, traps and drifting bowls are called a mooring.

Under the sediment trap funnel, little sample cups are connected that collect the material that falls down through the funnels. A computer system takes care that the cups are being replaced after a defined amount of days. At the position of “Laura” the traps were positioned at 1150 m and 1250 m water. During the last one and half years, the cups were replaced every 4 days.

Recovered sediment traps on the Backdeck of the R.V. Pelagia. Photo: K.Zonneveld

Large part of the particles that are being collected are formed by remains of plankton that was formed in the upper ocean and has taken up CO₂. By combining the information collected by the dust buoy “Laura” with the content of the buckets, information is received how dust input relates to the amount and composition of the sinking particles and the retrieval of CO₂ from the atmosphere.

Saturday 11.03.2023; “Mud and Cake”

Our Saturday morning started with the collection of ocean floor sediments with a multicore. This device is connected with a wire to the ship and is placed on the ocean floor (at our position 5200 m deep). Due to weights on top of the device, cores are “pushed” into the sediments after which lids close the top and bottom of the cores.

Katell and Runa “slicing” the first sediment core. Photo: K.Zonneveld

Oxygen sensor (the small needle sticking into the top of the sediment core) measuring sediment. Photo: K.Zonneveld

Measured oxygen profiles (x-axis = oxygen concentration (μmol/l), y-axis = depth in core (mm). Photo: K.Zonneveld

On deck part of the collected cores are sliced in parts, part of the cores are stored at -20°C to be further sampled and studied in Bremen. There we will study the amount and (molecular) composition of the organic particles that have been settled on the ocean floor. Some organic particles are prone to degradation when oxygen is present and as such release again CO₂into the ocean water. To obtain insight into this process, we measure the oxygen concentration in the upper part of the collected sediment cores immediately after recovery.

After recovering of the cores there was coffee with a surprise. One of the Pelagia crew members celebrated his birthday and the Alex the chef has treated us to a super delicious self made cake.

Monday 13.03.2023; “Transit”

We are sailing North, on “transit” to the region north east of the Cape Verden Islands where we hope to arrive on Wednesday morning.

During the transit we stop every day at eight o’clock in the morning to measure the properties of the water column and collect water samples. These water samples will be investigated on their plankton content by Catharina. She filters the collected water directly after collection but stores the filters for further investigations at her home University in Lissabon (Portugal).

Microscopic image of a tropical dinoflagellate (phytoplankton) recovered from the drifting trap (magnification 1000x). Photo: K. Zonneveld

The transit time is used by the MARUM team to investigate the particles collected by the drifting trap in the vicinity of the dust buoy “Laura”. These small traps are connected on a wire that in turn is connected to floating devices. The drifting traps are released in the water to drift freely with the currents. The traps were placed such that they collected particles at 100m, 200m and 400m water depth. During the transit we investigate what particles the trap collected. For this the collected material has been concentrated and put on microscopic slides to allow their investigation by light microscopy.

Tuesday 14.03.2023; “Hunting upwelling filaments”

By heading north, we are slowly leaving the nice warm tropical waters and arrive the first signs of colder waters prevailing off the Cape Blanc. This causes that for the first time this cruise we need to wear pullovers instead of t-shirts when we work on deck.

Satellite image of sea surface temperatures in the research area. Star represents the planned sample location (image with courtesy of the NASA state of the Ocean: https://soto.podaac.earthdatacloud.nasa.gov)

These colder waters have their origin near the coast of Cape Blanc. The prevailing winds from the northeast push the surface waters of the ocean away from the coast into the open ocean. These “pushed away waters” are being replaced with waters coming from the deeper parts of the ocean. This process is called upwelling. The upwelled waters are, apart of being colder than the surrounding waters, rich in nutrients that fertilize the upper ocean increasing the plankton production and as such the CO₂ storage in marine organic matter. The upwelled waters that are being “blown away” form large offshore drifting filaments of colder water. At the moment they can be observed at a distance of about 640 km from the coast (ca 340 nautical miles). Tomorrow we plan to investigate and sample waters of the distal part of one of these filament. This to obtain insight into the amount and composition of organic matter particles that sink to the ocean floor as well as their final fate in the deep ocean floor sediments.

For finding the location where to study these processes, we need information of the exact position of these highly dynamic filaments. We do this by studying satellite images of sea surface temperatures provided by the NASA “state of the ocean” project: https://soto.podaac.earthdatacloud.nasa.gov

Wednesday 15.03.2023; “sampling, sampling, sampling”

West off Cape Blanc 20.2407 N, 20.7812 W.

After a beautiful sunrise we arrived at the distal part of the Cape Blanc upwelling filament. Because of the Sahara dust in the air the rising sun was colored more orange as normal and the air looks as if a slight orange filter has been placed in front of our eyes.

Deployment of the drifting trap in the early morning. Photo: K. Zonneveld

We started the day with the release of the drifting trap that will drift with the filament waters to collect for 24 hours sinking particles from the upper waters. Then we sampled the particles in the deeper waters just above the sea floor at 3988 m and 3983 m depth with in-situ pumps.

Recovery of the multicore in the late evening. The blue colors are the result of the blue lights that illuminate the working deck during the night. This light is less disturbing for ocean birds than normal white lights. Photo: K. Zonneveld

These are a sort of underwater vacuum cleaners that pump waters through a filter, in our case about 800 liters. The sampling ended for us with the sampling of surface sediment samples with the multicore. All devices worked perfectly and after a very long day of sampling we feel extremely tired but very satisfied.

Thursday 16.03.2023; “Dolphins and “Carmen” on the loose”

Off Cape Blanc 21.22 N, 21.0348 W.

Today we arrived at the location of the second dust buoy “Carmen” … at least, where “Carmen” should have been. “Carmen” is equipped with a sensor that gives every two hours a signal about her exact position. This is received in the control room at the Royal Netherlands Institute of Sea Research. Earlier this year it was visible that the position of Carmen suddenly moved towards the more central Atlantic Ocean … for some reason the cable that connected her to the anchor had broken and she started to drift with the currents.

Fortunately, another research vessel could pick her up and bring her safely to Mindelo. There we collected her and she is now waiting on the back deck to be released into the ocean again.

However, before we can do that, we first have to recover the rest of the cable that is still in the water and connected to the anchor. This cable has a length of 4 km and since it was loose in the water for several months there is a large change that it has become knotted. We therefore need some luck during the recovery that the “knotting” has not been too severe.

Luck we might have as on the transit between the last station and the position of Carmen we were accompanied for almost half an hour by a group of about 40 dolphins. The Dolphins “played” in front wave of the ship and we were treated to a real dolphin show. In many “Sea -tales” dolphins are “luck bringers” to the ship they accompanied and its crew and we hope this might come true. At least it brought a big smile on all of our faces to see these beautiful animals in their element.

Dolphins in front of the ship. Video: K. Zonneveld