Join the researchers on board R/V Skagerak as they travel to the Gotland Deep from 28 June to 19 July. Here, the researchers share their own experiences and glimpses of life and work on board – from underwater instruments and sampling to everyday life on a high-tech research vessel.
What happens on board?
RECLESS: Baltic 2026 is an expedition investigating how oxygen deficiency affects the nitrogen cycle in the ocean – and what this may mean for the Baltic Sea ecosystem and the ocean’s role in the climate system. During the expedition, the researchers collect water samples and carry out advanced measurements of oxygen, nitrogen and microbial processes in the oxygen-deficient water masses of the Gotland Deep. The blog follows the work behind the science: instruments being lowered into the depths, samples being processed in the laboratories on board, analyses that begin while still at sea – and everyday life for researchers and crew during three intensive weeks on R/V Skagerak.
Facts about the expedition
Expedition: RECLESS: Baltic 2026 Location: Gotland Deep, Baltic Sea Period: 28 June–19 July 2026 Vessel: R/V Skagerak Research focus: Oxygen deficiency, the nitrogen cycle, microorganisms and climate connections
Thirteen researchers from the international team contribute texts to the blog.
The expedition is led by Laura Bristow, a marine biogeochemist at the Department of Marine Sciences, University of Gothenburg.
The RECLESS project is funded by the European Union. The views and opinions expressed in the blog are those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them.
An in situ incubator is one of the instruments used during the expedition to study what happens in oxygen-deficient areas of the ocean.
Photo: Alex Ingle, Schmidt Ocean Institute
Day 1: A floating laboratory takes shape
29 June 2026 – By Laura Bristow
"After months of planning and preparation, yesterday we joined R/V Skagerak in Oskarshamn for the first RECLESS expedition of the year.
Scientific equipment, gas cylinders and boxes of sampling gear were loaded onboard as we began transforming the ship into a floating laboratory. There was plenty of excitement as researchers, students and technicians from partner institutions in Europe and the United States came together and prepared for the weeks ahead.
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R/V Skagerak in Oskarshamn, ready for departure.
Photo: Laura Bristow
Today we left port and began our transit towards the Gotland Deep in the central Baltic Sea. This low-oxygen environment provides a natural laboratory for understanding how microbial communities respond to changing oxygen conditions and how they influence the cycling of carbon and nitrogen.
Over the coming weeks we will collect water samples, deploy a range of oceanographic instruments — including a novel in situ incubation system — and make measurements that will help us better understand how these ecosystems function and how they may respond to future environmental change.
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A lot of action in the main laboratory on board R/V Skagerak.
Photo: Laura Bristow
...we began transforming the ship into a floating laboratory
The calm weather has given us a perfect start. As R/V Skagerak heads east, we are unpacking the last boxes, setting up the laboratories and making the final preparations before sampling begins. Tomorrow we arrive at our first station, where the scientific work begins. Stay tuned as we share life aboard R/V Skagerak and take you behind the scenes of the RECLESS expedition."
Towards the horizon!
Photo: Laura Bristow
On board R/V Skagerak.
Photo: Laura Bristow
Laura Bristow, a marine biogeochemist at the University of Gothenburg, leads the expedition on board R/V Skagerak.
Photo: Agnes Faxén
Day 3: An underwater laboratory
1 July 2026 – By Morten Larsen
"Today we deployed one of the most exciting pieces of equipment on board R/V Skagerak.
Once lowered beneath the surface, our two incubators become small autonomous laboratories, carrying out experiments under the natural environmental conditions experienced by the microbes.
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Lowering the main flotation sphere, that keeps the incubators floating in the waters beneath the R/V Skagerak. Chris Basque (WHOI), Morten Larsen (SDU), Törner Hansson (R/V Skagerak)
Photo: Oskar Wandgell
Many studies of microbial activity begin by bringing water from depth back to the ship. But for microbes living in the Baltic Sea’s low-oxygen waters, this journey can change their environment. As the water is brought to the surface, pressure decreases, temperature increases and oxygen can enter the sample, potentially changing microbial activity before measurements even begin.
Our solution is to carry out the experiments where the microbes are.
The instruments, called in situ incubators, collect seawater directly at depth and keep it under its natural temperature, pressure and oxygen conditions. They then add stable-isotope tracers – harmless labels that allow us to measure how microbes process carbon and nitrogen.
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Installing the acoustic releaser on the main flotation sphere. Chris Basque (WHOI), Morten Larsen (SDU).
Photo: Oskar Wangdell
Our solution is to carry out the experiments where the microbes are.
Over the next 32 hours, the incubators will automatically collect and preserve a series of samples, creating a timeline of microbial activity without ever exposing the water to oxygen.
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Final inspection of the incubators before they go into the water. Chris Basque (WHOI), Morten Larsen (SDU), Laura Bristow (GU).
Photo: Oskar Wangdell
While we continue working in the laboratories on board R/V Skagerak, our underwater laboratories are quietly carrying out their own experiments many metres below us.
We are looking forward to recovering the incubators and discovering what the microbes have been doing beneath the surface."
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Incubators are ready and prepared for deployment.
Photo: Oskar Wangell
Lowering the incubators over the side of R/V Skagerak. Chris Basque (WHOI), Morten Larsen (SDU), Tørner Hansson (R/V Skagerak)
Photo: Oskar Wangdell
Day 5: Catching microbes
5 July 2026 – By Maria Pachiadaki
"The Baltic Sea can look calm from the deck. Today the sea shifted between grey and silver, with clouds stretching across the horizon. But beneath R/V Skagerak, the water column is anything but simple. Oxygen, chemical compounds, and microbes change dramatically with depth.
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View from R/V Skagerak,
Photo: Maria Pachiadaki
The Gotland Deep has layers of water with very little oxygen. The microbes living there are adapted to this environment. If we bring water all the way back to the ship before preserving it, their world changes quickly. Temperature, pressure and oxygen can all shift during recovery.
The Microbial Sampler helps us avoid this problem. At first glance, it looks like a metal frame with small containers, tubes and cables. But for us, it is another key instrument on board.
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The Microbial Sampler is deployed from R/V Skagerak
Photo: Maria Pachiadaki
We lower it from R/V Skagerak to the depth we want to sample. Once there, it pumps seawater through small filters that trap microbial cells. The samples are then preserved close to where the microbes were living, capturing them before their environment has a chance to change.
Chris Basque (WHOI) and Peter Barthelsson (R/V Skagerak, at the winch, not shown in the photo) deploy the Microbial Sampler. It will spend several hours at depth collecting and preserving microbes.
Photo: Maria Pachiadaki
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Close-up of the Microbial Sampler after recovery. The blue containers contain the filters that have captured the microbes from the Baltic Sea.
Photo: Oskar Wangdell
Each filter may contain thousands or even millions of cells from a single layer of the Baltic Sea. These samples will later help us identify which microbes are present, which genes they carry, and which processes they are actively using in low-oxygen water.
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Once the Microbial Sampler is back aboard R/V Skagerak, the filters (inside the blue containers) are transferred to small tubes and frozen until processing back in the home laboratory.
Photo: Maria Pachiadaki
Each filter may contain thousands or even millions of cells from a single layer of the Baltic Sea.
While other instruments measure the chemistry or carry out incubations, this Microbial Sampler captures the biological story. Together, the measurements and samples collected aboard R/V Skagerak will help us connect the changing conditions in the Baltic Sea to the microbes that live there and the processes they perform."
