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While the JOIDES Resolution makes its way back to Reykjavík through some rocking seas, the ship’s scientists have a bit more time to reflect on their work. We chatted with Expedition 400 paleoecologist Dr. Heike Zimmermann of the Geological Survey of Denmark and Greenland. She discusses her research and how it ties in with the expedition science objectives. 

What can we learn from ancient life in seafloor sediments?

A closeup of a shell cross-section and tiny planktonic organisms
Most of our knowledge about past ecosystems comes from tiny algae that lived in the ocean and left biomineral remains such as (A) siliceous diatoms, (B) calcareous foraminifera or (C) shells from Molluscs or Brachiopods. (D) Fossilized burrows (darker areas) are proof of ancient life in the seafloor and abundant food supply from the sea surface. But who left these traces? And what has lived in the waters above that did not leave any remains? The only traces of soft, squishy organisms without hard parts may be ancient DNA! Credits: IODP

Seafloor sediments are natural archives that can tell us how ecosystems have changed in the past. Our planet has experienced many cycles of warmer and colder phases and species have evolved, adapted, shifted where they live, or even died out as a consequence. Normally with lab experiments, we can only see a fraction of the complexity of species interactions and feedback mechanisms. But, with seafloor sediments, we can look at the past and use them like a big experiment!

Which tool do you use to get information about past ecosystems?

Many lifeforms with important roles in marine ecosystems are not typically preserved as fossils. Among those are important species of phyto- and zooplankton, jellyfish, worms, or fish. However, we can find molecular traces of these organisms, such as DNA. DNA can bind to sediment particles and get preserved over thousands to millions of years. We call this “sedimentary ancient DNA”.

What methods and tools do you use to collect and analyze DNA from seafloor sediment?

Once the DNA is extracted from the sediments, my colleagues and I will apply a variety of methods, one being metagenomic shotgun sequencing. From just a few grams of sediment, shotgun sequencing allows us to reconstruct marine communities from bacteria and the tiniest alga to marine mammals in a single reaction!

What is the most exciting part of your work on this expedition?

It’s like a treasure hunt!

We get the chance to unfold the environmental history of Northwest Greenland over the last few millions of years. These sediments are the oldest I have ever worked with! It’s spectacular to see sediments that have been buried so deep and that are usually beyond our reach with standard coring equipment. I am feeling very fortunate to work on such precious and unique material.

A person in a white body suit with a mask and goggles an blue plastic gloves is digging into sediment.
Sedimentary ancient DNA is very susceptible to contamination. I therefore suit up to protect the ancient samples from my own DNA. Credits: Erick Bravo, IODP

How do you “dress for the job” of collecting samples?

I “suit up” into a plastic coverall, I wear a face mask, a hairnet and gloves. Ancient DNA is very sensitive to contamination by modern DNA either from myself or from the surrounding environment. Normally, when DNA is contained within a living cell, any damage to it is instantly repaired. But after an organism dies, its DNA degrades into small fragments and gets increasingly damaged over time. The older the sample, the fewer and shorter DNA molecules we expect to find, and if I am not careful enough, my DNA could override the ancient signals we are looking for.

How does your research connect with the Expedition 400 science objectives?

I hope to improve our understanding of the interactions between climate, the ocean, and the biosphere in the Arctic. The samples I have taken contain valuable information about climate-ecosystem interactions and how marine ecosystems respond to the deglaciation of the Greenland Ice Sheet. My research addresses questions like: What might happen to primary productivity and the biological carbon pump if the ice sheet melts and releases its freshwater into the ocean? How might food webs change and what might be the effect on economically relevant fish stocks? Could Greenland be more susceptible to harmful algae blooms in the future?

Marine ecosystems are important resources to us humans and

I hope ancient DNA can improve our understanding of past, current, and future ocean conditions.

Heike Zimmermann: Expedition 400 Paleoecologist

Ocean Acidification

Between Storms and Science: Easter in the Labrador Sea (04.04.26–13.04.26)

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Between all the scientific work, we celebrated Easter on board, although the weather had other plans for us. Due to rough conditions, we weren’t able to carry out any CTD casts.

Photo: Sarah Tomae

Easter itself was spent in a mix of rest and small celebrations. Some of us enjoyed a long Easter breakfast with traditional Easter bread, while others took the opportunity to sleep in. In the evening, we gathered with both crew and scientists for a small celebration. The ship’s cook even organized a quiz, and those who answered correctly were rewarded with Easter chocolate.

The next day, the weather improved, and we began early with the recovery of K1, a 3,495-meter-long mooring in the middle of the Labrador Sea.

We joined the nautical officers on the bridge before sunrise to search for it. Fortunately, K1 has a floating buoy with a light, so we were able to spot it even in the dark. The actual recovery started at first light, and it began to snow while we were working.

Photo: Sarah Tomae, GEOMAR

Amid all the CTDs and mooring operations, there was also a personal highlight: my (Sarah’s) birthday. Although I’ve spent birthdays away from home before, this one felt especially unique, being so far out at sea, with only limited internet contact.

Normally, I work the 4-8 shift, but my incredibly kind shift team gave me the morning off. That meant I could sleep in and even find time to call family and friends back home. In the afternoon, I was surprised with my favourite cake, baked by Julia.

Our work continued with the mooring array at 53°N, which consists of seven moorings. So far, we have recovered five (K7, K8, K9, DSOW1 and DSOW2), and three of them have already been redeployed (K7, K8 and DSOW1,).

Deploying K7 turned out to be particularly tricky. On our first attempt, sea ice drifted toward us faster than expected, forcing us to recover nearly half of the mooring again. While the ship itself can handle drifting ice, deploying a mooring is much more delicate: a long cable with instruments and floats is released behind the ship before the anchor is dropped, allowing the system to sink into place.

Two days later, we tried again and this time, the deployment was successful.

Photo: Sarah Tomae

Afterwards, we moved closer to the sea ice, which was a highlight for many of us. Seeing the ice up close and even spotting a seal swimming nearby, made the experience unforgettable.

Photo: Sarah Tomae
Photo: Sascha Gniosdorz

Due to the continuing harsh weather, the decision was made to return to K1 and make use of an upcoming weather window for deployment the following day.

German:

Zwischen Stürmen und Wissenschaft: Ostern in der Labradorsee (04.04.26 – 13.04.26)

Zwischen all der wissenschaftlichen Arbeit haben wir Ostern an Bord gefeiert, auch wenn das Wetter andere Pläne für uns hatte. Aufgrund der rauen Bedingungen konnten wir keine CTD-Messungen durchführen (Messungen von Leitfähigkeit, Temperatur und Tiefe im Ozean).

Foto: Sarah Tomae

Ostern selbst war eine Mischung aus Erholung und kleinen Feierlichkeiten. Einige von uns genossen ein ausgedehntes Osterfrühstück mit traditionellem Osterbrot, während andere die Gelegenheit nutzten, etwas länger zu schlafen. Am Abend kamen Crew und Wissenschaftler*innen zu einer kleinen Feier zusammen. Der Koch organisierte sogar ein Quiz, und wer die Fragen richtig beantwortete, wurde mit Oster-Schokolade belohnt.

Am nächsten Tag besserte sich das Wetter, und wir begannen früh mit der Bergung von K1, einer 3.495 Meter langen Verankerung mitten in der Labradorsee. (Eine Verankerung ist eine lange, am Meeresboden befestigter Draht, der mit Instrumenten ausgestattet ist, um über längere Zeit Ozeandaten zu messen.)

Noch vor Sonnenaufgang gingen wir mit den nautischen Offizieren auf die Brücke, um nach ihr Ausschau zu halten. Glücklicherweise verfügt K1 über eine schwimmende Boje mit Licht, sodass wir sie bereits im Dunkeln entdecken konnten. Die eigentliche Bergung begann bei Tagesanbruch und es begann sogar zu schneien.

Foto: Sarah Tomae

Zwischen all den CTD-Einsätzen und Verankerungsarbeiten gab es auch ein persönliches Highlight: meinen (Sarahs) Geburtstag. Obwohl ich schon öfter Geburtstage fernab von zu Hause verbracht habe, war dieser besonders, so weit draußen auf dem Meer und mit nur eingeschränktem Internetkontakt.

Normalerweise arbeite ich in der 4-8 Uhr Schicht, aber mein unglaublich nettes Schichtteam hat mir den Morgendienst freigegeben. So konnte ich etwas länger schlafen und hatte sogar Zeit, mit Familie und Freunden zu Hause zu telefonieren. Am Nachmittag wurde ich dann noch mit meinem Lieblingskuchen überrascht, den Julia für mich gebacken hat.

Unsere Arbeit ging weiter mit dem Verankerungs-Array bei 53°, das aus sieben Verankerungen besteht. Bisher haben wir fünf geborgen (DSOW1, DSOW2, K7, K8 und K9), von denen drei bereits wieder ausgebracht wurden (DSOW1, K7 und K8).

Das Ausbringen von K7 erwies sich als besonders schwierig. Beim ersten Versuch trieb das Meereis schneller auf uns zu als erwartet, sodass wir fast die Hälfte der Verankerung wieder einholen mussten. Obwohl das Schiff selbst gut durch treibendes Eis navigieren kann, ist das Ausbringen einer Verankerung deutlich anspruchsvoller: Dabei wird ein langer Draht mit Messinstrumenten und Auftriebskörpern hinter dem Schiff ausgesetzt, bevor am Ende der Anker gelöst wird und das gesamte System absinkt.

Zwei Tage später versuchten wir es erneut, diesmal mit Erfolg.

Foto: Sarah Tomae

Anschließend fuhren wir näher an das Meereis heran, was für viele von uns ein besonderes Highlight war. Das Eis aus nächster Nähe zu sehen und sogar eine Robbe in der Nähe schwimmen zu beobachten, machte das Erlebnis unvergesslich.

Foto: Sarah Tomae
Foto: Sascha Gniosdorz

Aufgrund der weiterhin rauen Wetterbedingungen wurde schließlich entschieden, zu K1 zurückzukehren, um ein bevorstehendes Wetterfenster für die Ausbringung am nächsten Tag zu nutzen.

Between Storms and Science: Easter in the Labrador Sea (04.04.26–13.04.26)

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Ocean Acidification

Humans Just Flew Around the Moon This Week. But Would Babies Born There Ever Truly Feel Gravity? Ask Jellyfish Babies.

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This week, NASA’s Artemis II crew made history by flying around the Moon and returning safely to Earth, the first human journey to the Moon’s vicinity in more than 50 years. It was a stunning reminder that humanity is no longer just dreaming about living beyond Earth. We are actively rehearsing for it.

And that leads to a much stranger, deeper question: even if one day we build skyscrapers on the Moon, raise families there, and turn space into a place to live, will babies born away from Earth develop a normal sense of gravity? Or will their bodies learn the universe differently?

To explore that question, NASA once turned to an unexpected stand-in for human babies: jellyfish babies. On the STS-40 mission, scientists sent thousands of tiny jellyfish polyps into space because jellyfish, like humans, rely on gravity-sensing structures to orient themselves. The experiment asked a simple but profound question: if a living body develops in microgravity, will it still know how to handle gravity later?

The answer was both fascinating and unsettling. The jellyfish developed in space in large numbers, but once back under Earth’s gravity, the ones that had developed in microgravity showed far more pulsing abnormalities than the Earth-grown controls. In other words, their bodies formed, but their sense of balance did not seem to work quite the same way.

That is why this old jellyfish experiment still matters today. Before we imagine lunar cities, schools, nurseries, and generations born off-world, we need to ask not only whether humans can survive in space, but whether developing there changes how the body understands something as basic as up, down, and movement. Jellyfish babies cannot tell us everything about human children, but they may have given us one of the first clues that life born beyond Earth might not come home unchanged.

Reference: https://nlsp.nasa.gov/view/lsdapub/lsda_experiment/0c10d660-6b12-573d-8c3b-e20e071aed3b

Image: GEOMAR, Sarah Uphoff

Humans Just Flew Around the Moon This Week. But Would Babies Born There Ever Truly Feel Gravity? Ask Jellyfish Babies.

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Ocean Acidification

First Week of Cruise MSM142 – Into the Labrador Sea

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After a slight delay of the Maria S. Merian caused by late-arriving containers our research cruise MSM142 finally got underway. By last Tuesday (24.03.2026), the full scientific team had arrived in Nuuk, the capital of Greenland, and the ship reached port on Wednesday (25.03.2026) morning. That same day, scientists and technicians moved on board and immediately began preparations, assembling and testing our instruments. Although the mornings on Wednesday and Thursday were grey and overcast, the afternoons cleared up beautifully. This gave us valuable time to organize equipment on deck and store empty boxes back into the containers before departure.

Foto: Julia Pelle

Given the forecast of harsh conditions outside the fjord, we carried out the mandatory safety drill while still in harbour. This included practicing emergency procedures and boarding the lifeboat. After completing border control, we were finally ready to leave Nuuk. We set sail on March 27th, heading into the Labrador Sea to begin our mission. Even before starting scientific operations, we tested the setup for deploying our gliders without releasing them during the transit out of the fjord. Once we reached open waters, we were met by high waves the following morning. For some on board, this was their first experience under such rough sea conditions. Seasickness quickly became a challenge for a few, while scientific work had to be temporarily postponed due to the strong winds and sea conditions. Together with the crew, we discussed how best to adapt our measurement plans to the given weather conditions. On March 29th, we were finally able to begin our scientific program with the first CTD deployment. A CTD is an instrument used to measure conductivity, temperature, and depth, which are key parameters for understanding ocean structure.  

Foto: Julia Pelle

During the following night, we continued with additional CTD stations and successfully recovered two moorings: DSOW 3 and DSOW 4, located south of Greenland. These moorings carry instruments at various depths that measure velocity, temperature, and salinity. DSOW 4 was redeployed on the same day, while DSOW 3 followed the next day. In addition, the bottles attached to the CTD’s rosette can be used to collect water samples from any desired depth. These samples can be used, for example, to determine the oxygen content, nutrient levels, and organic matter.

Foto: Julia Pelle

Both are part of the OSNAP array, a network of moorings spanning the subpolar North Atlantic. On these moorings are a few instruments, for example microcats which measure temperature, pressure and salinity.

We then conducted around 25 CTD stations spaced approximately 3 nautical miles apart across an Irminger ring identified from satellite data. This high-resolution sampling was necessary to capture the structure of an Irminger Ring, which had a radius of about 12 km wide.

Foto: Julia Pelle

The days leading up to April 2nd were marked by very rough weather conditions. Life on board became both challenging and, at times, unintentionally entertaining sliding chairs were not uncommon. During the night from April 1st to April 2nd, winds reached 11 Beaufort with gusts up to 65 knots, forcing us to pause our measurements. Fortunately, conditions improved by morning, allowing us to resume our work. As well as with the help of the crew we had to adapt to the harsh weather conditions to continue our scientific work. On the 3rd of April, we were able to deploy a few gliders and one float. An ocean glider is an autonomous underwater Vehicle, which you can steer remotely and send to different locations, while it is measuring oceanographic key parameters.

Foto: Julia Pelle

This research cruise focuses on understanding small-scale processes in the ocean and their connection to the spring bloom, an essential phase in marine ecosystem in subpolar regions. Despite the challenging start, we have already gathered valuable data and look forward to the weeks ahead in the Labrador Sea. 

First Week of Cruise MSM142 – Into the Labrador Sea

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