Jack Wilkin (UK)
During April and May 2022, I had the fantastic opportunity to participate in a research expedition to the North Sea and Iceland on the RRS Discovery, as part of the SEACHANGE project. The following article is a brief description of the science that happened on the ship.
What is the SEACHANGE Project?
SEACHANGE is a six-year research project funded by the ERC Synergy Grant Scheme (part of the EU’s research and innovation programme, Horizon 2020). It is jointly run by the University of Exeter (UK), Johannes Gutenberg University Mainz (Germany) and the University of Copenhagen (Denmark).
This is a collaborative project with scientists worldwide, from master’s students to professors working diligently to answer the question: What were the oceans like before large-scale human impact? To answer this question, we need to test the scale and rate of biodiversity loss resulting from fishing, whaling and habitat destruction over the last 2,000 years in the North Sea and around Iceland, eastern Australia and the Antarctic Peninsula. In addition, we need to find out more about the earlier transition from hunter-gatherer to farming communities in northern Europe around 6,000 years ago.
However, before answering this question and starting to generate data, we first needed the raw materials. Because we were monitoring the oceans, we needed to go to the sea to gather our samples, so we need a boat … a very big boat.
The RRS Discovery.
The RRS Discovery (Fig. 1) is one of the most advanced research ships in the world. It is a 100m long and is operated by the National Oceanography Centre (NOC) based in Southampton, UK. Since its first expedition in 2013, the Discovery has successfully traversed the world’s oceans from Antarctica to the Arctic and everything in between, to learn more about our oceans, both past, present and future.
Life on board the Discovery was fantastic– except for seasickness – with each scientist on board having their own cabin (the Chief Scientific Officer even had a living room); there’s also a bar/games room, a shop called the Bond to buy shirts and souvenirs for friends and family back home, and also a gym which came in handy given how great the food was!
The Discovery is a floating laboratory with a range of workspaces that can be flexibly configured to support the diverse range of research done on the ship. The labs are situated on the main deck with additional lab space on the back deck, and specialist laboratories can be provided by using converted shipping containers. The Discovery has 389m2 of laboratory space and enough room for up to seven, 20-foot containers on deck. There is also ample storage space in fridges and freezers for the material we collected.
Working in a scientific laboratory can be challenging at times, even when you are perfectly stationary. And working in one that is constantly rolling around presented a unique set of challenges. Thankfully, everything on the ship is either bolted to the floor, stored in a cabinet or behind a bungee cord, which was particularly handy around Iceland. The fantastic experience of being able to work in a facility like this made the occasional 30° tilt more than worth it.
A virtual tour of the ship is available on the NOC website (https://noc.ac.uk/facilities/ships/rrs-discovery/rrs-discovery-virtual-tour). You can also find out where the Discovery has been and where it is off to next on the NOC website (https://noc.ac.uk/science/previous-expeditions).
Where did we go?
Due to the ongoing Covid Pandemic, we had to take certain precautions, such as social distancing and regular testing for the first week, during which we needed to remain in port. This first week gave us an excellent opportunity to get to know each other, explore the ship, learn how to use some of the equipment, and have talks by different scientists from all career stages on their research (the “Floating University”).
We visited dozens of different sites in five different locations (Skagerrak, the Fladen Ground, Shetlands, Orkney, and Iceland; Fig. 2). Following our week in the dock in Southampton (1), we set off early Saturday morning (16 May 2022) on calm seas heading east through the English Channel to the Skagerrak (2). After spending a few days here, we headed north to the Fladen Ground (3), a basin in the upper part of the North Sea full of oilrigs and, to be honest, not a lot else.
The lack of material from the Fladen Ground is due to human activity over the past millennia. The continuous fishing, industrial activity and dredging have left the North Sea mostly empty. It is an industrial landscape, just as affected by human activity as the Canadian Oil Sands or the coal mines in northern England. Because it is hidden under the waves, we tend to think about it less, and thus, less care is spent on trying to project marine ecosystems hence the importance of projects like SEACHANGE.
After leaving the Fladen Ground, we travelled further north to the Shetlands (4) and Orkney (5). Then we had a three-day transit to the North Icelandic Shelf (6), where we spent the next week working in different locations both within and just outside the Arctic Circle before disembarking in Reykjavik on the 11 May 2022 (7).
Out of these different locations, my favourite was Iceland. This was because we were able to get the best data from here. When we were in the north Icelandic shelf, there was a large storm in the Denmark Strait which forced the ship to take shelter in Ísafjarðardjúp (a fjord in North Iceland). Here we saw several humpback whales, which were presumably also sheltering from the storm and a group of puffins. Being able to get so close to such majestic animals was simply incredible. Seeing the sheer beauty of this country; seeing the mountains of northern Iceland was a good reminder of why I love geology (Fig. 3).
Marine Mammal Observing (MMO)
The first thing that needed to happen before we did any other work was to find out if there were any whales or dolphins around. This was done for the safety of these amazing animals. The North Sea, especially the region around the Scottish islands and the Icelandic shelf, has many cetaceans. Geophysics causes cetaceans to become disorientated and even beach themselves. It was essential to ensure that no cetaceans were within 500m of the ship (beyond that point, they still don’t like it but can swim away without being disoriented.
The MMO took place for 30 minutes in water shallower than 200m and one hour in water greater than 200m before geophysics. Every time a whale or dolphin was spotted within the 500m radius, another 20 minutes was added from the time of the last sighting. During our time at sea, we did see quite a few whales, especially the closer we got to Iceland, but thankfully, they did not interfere with the other work.
Geophysics was used to scan the seafloor to determine where the coring and dredging should take place using a multibeam echo-sounder transducer, which can map 500m on either side of the ship in exquisite detail. Geophysics disorientates marine mammals, hence the importance of doing the MMO before starting this process.
Water from different depths was collected from multiple sites during the trip. This was achieved using CTD (conductivity, temperature, depth) sampling that provides real-time, accurate and precise data from the water column that can bring up to 24 samples of 10 or 20 litres, at predetermined depths back up to the surface.
Some of the water samples extracted from DY150 will be sent to the University of Copenhagen for environmental DNA (eDNA) analysis, an exciting emerging discipline that has revolutionised how we conduct ecological studies. What makes eDNA so interesting is that it tells you everything that is living in an environment from the smallest microbes to whales. The biggest problem in ecological studies is that the sampling is biased towards larger organisms, with microorganisms and fungi often being overlooked. This is despite making up the bulk of ecosystem diversity and providing more information about the health of an environment than mammals or birds.
As with most things in science, you need to be acutely aware of cross-contamination, and this is particularly important when dealing with DNA. As such, access to the eDNA lab was closely controlled. On the ship, the eDNA samples were carefully processed and stored in the freezers. Much of the eDNA work was done by the team from Copenhagen, which has one of the most sophisticated eDNA facilities in the world.
Another use for the water is for the study of microplastics (plastics that are below five millimetres in size) being done by Dan Wilson (University of Exeter), who brought an extensive collection of very breakable looking glass jars and vials. But thanks to cardboard boxes and liberal application of bungee cords, no glassware was broken, at least at the time of article submission. Microplastics have the potential to remain in the water column for decades, contaminating our oceans and entering the food chain. However, how plastics circulate around the world’s oceans is still poorly understood and collecting water samples can help refine computer models and monitor plastic pollution in our oceans.
Multicores (Fig. 4) are relatively short cores (of about 30cm) that include only the top part of the sediment so they are perfect for high-resolution studies of the recent past. These cores will be incredibly useful in determining the environmental impact of overfishing. Some of the material is also being sampled for eDNA.
Sections of the multicores were placed into a tin foil-lined Petri dish to prevent the sediment from contacting the plastic, limiting the amount of cross-contamination, which can alter the geochemistry. Being so recent means that sediments are not yet consolidated, so processing them is a very messy process. To get the one centimetre of material, the cores were lowered onto a pillar of a slightly narrower diameter inside the core to push the sediment out. The lowering was carefully monitored, and each centimetre of material was transported to the aforementioned Petri dishes.
My main role on DY150 was working on the piston and gravity cores during the midnight to midday shift. Piston and gravity cores (Fig. 5) are the bread and butter of palaeoclimate analysis, with the oldest ocean cores dating to the Cretaceous.
From these marine records, scientists have been able to reconstruct past climates throughout the Cenozoic with remarkable precision using a wide range of proxies which include:
- Sedimentary logging and facies analysis;
- microfossil and nannofossil assemblages;
- eDNA (members of the Copenhagen team may be visiting the Penryn Campus later in the year to do some DNA work on some of the cores); and
- geochemistry (both from fossils and sediments).
Both core types differ in terms of deployment. Gravity cores go into the sediment under the weight of gravity (hence the name) and tend to be shorter than the piston cores making them perfect for studying the Holocene (the amount of time preserved depends on the sedimentation rate). Piston cores, in contrast, have a piston (again, hence the name), which forms a vacuum that helps maintain the core inside the barrel, so we can get higher quality and longer cores, allowing us insights into climate change in the more distant past (Fig. 6). The longest piston cores we could use on the Discovery were24m long.
A core cutter was brought along to help speed up the cutting process. It used a couple of rotating blades (one on either side) to get very close to cutting the plastic lining. Behind these were Stanley knives that finished the job (the blades would have disrupted the sediment too much). And finally, cheese wire sliced the mud into two equal sections. One section was immediately placed in storage, and the second was moved into the chemistry lab to have a sedimentary log made.
In total, 22 cores were collected with a total of 127m of sediment, and each one had a sedimentary log recorded with facies and key features (e.g. shells) recorded. The longest piston core was nearly 19m from the North Icelandic Shelf. What was especially nice was that the cores from northern Iceland had the volcanic ash layers that can be used to accurately date the sediments helping refine future age/depth models.
The final working group and the last to collect their samples were the dredging team, who dredged up shells belonging to the bivalve Arctica islandica from the seafloor. Sclerochronology is a dating method that relies on counting the growth increments of shells, which can be counted back from a known time of death so the exact date of each increment can be determined – the same principle used in dendrochronology.
By identifying characteristic patterns in the growth cycle (e.g. five growth lines close together), you can match this with another shell, then another and another, and so on (Fig. 7). Using hundreds of shells, you can construct long and detailed age sequences dating back millennia. As you can probably guess, the task is incredibly time-consuming. To help speed the process along, the expedition’s Senior Scientist Dr David Reynolds (University of Exeter) has developed a statistical package called RingdateR to help automate the growth line counting.
Arctica islandica is the most widely used species in the North Atlantic because it is very common in the region and long-lived (over 500 years). The growth increments are pretty clear – at least compared to many other species. The shells can also be analysed for different geochemical proxies (e.g. oxygen and carbon isotopes) that can tell us about ocean chemistry and temperature through time. Sclerochronology has also been used to date archaeological sites in Northern Europe and the east coast of North America.
The dredging team collected ten live shells from each site, with the rest of the material collected being already dead and of undetermined age. In all, over 20,000 Arctica were collected, with the bulk of these finds coming from the North Icelandic shelf (Fig. 8).
Collecting the material is just the beginning of the scientific process. The next step will be the rigorous processing of data, analysis, writing up and peer review, which can take years. The samples collected during DY150 will be sent to various institutions to be worked on by academics for years to come. Given the nature of the SEACHANGE project and Horizon 2020’s importance to the EU, the conclusions from this research could very well influence marine conservation efforts at a global level. An official report will be written up, and links to the papers written as part of the SEACHANGE project will appear on its website when published (https://seachange-erc.eu/publications).
For more information on the techniques used, readers are directed toward the DY150 Cruise Report, which will be made available to the public following its completion on the British Oceanographic Data Centre website (https://www.bodc.ac.uk/).
I would like to thank the incredible crew and technicians on the Discovery,who are the ones making all this possible. Professor James Scourse and Dr Sev Kender (both University of Exeter) for allowing me to be a part of this fantastic experience and Em Squire (University of Exeter) for organising the SEACHANGE project.
I would also like to thank all of the DY150 Scientists, with special thanks to Matt Mason (University of Exeter) for double-checking the sclerochronology section; Dan Wilson (University of Exeter) for looking over the water collecting section, Dr Luke Holman (University of Copenhagen) for clarifying some points on the eDNA work. I would also like to thank the gravity/piston coring team: Laura Byrne, Jane Earl and Charlotte Greenall (all University of Exeter), and also Dr Harry Robson and Ellie Nelson (both University of York) for helping during the nightshift in-between “DredgeFest”. Finally, I’d like to thank the MMO team (Zoë Heard and Dani Crowley; University of Exeter) for spotting so many whales, dolphins and puffins. The five weeks I spent with all of you were some of the best of my life and I’ll cherish these moments forever.
About the author
I am a PhD student and PTA in geology/palaeontology at the Camborne School of Mines (University of Exeter), working on sediment cores from South Georgia. The project aims to reconstruct the post-deglacial environment of South Georgia using diatom/foraminiferal assemblages and geochemistry.