It's early morning and the sea and land teams from the gigantic Traversing European Coastlines project (TREC) are waking up in their cabins on board Electra af Askö, Stockholm University's research vessel based at the Askö Laboratory in the Trosa archipelago.

The expedition started at the end of March in Brittany, and has since travelled along the coasts of France, Belgium, the Netherlands, Germany, Denmark, Poland, the Baltic States and Finland. Now it has come to Sweden and Askö, and a long day of sampling along transects from the sea and into the coastal forest awaits.

Collaboration with research stations

The expedition is a gigantic pan-European project, led by the European Molecular Biology Laboratory, headquartered in Heidelberg, Germany, in collaboration with a large number of marine research stations across Europe. It just arrived from Askö's sister station at the mouth of the Gulf of Finland – Tvärminne Zoological Station, via Åbo Akademi University. After the stop at Askö, it will continue to Kristineberg Center on the Swedish west coast. From there the journey continues to Norway, Great Britain and Ireland and down along the Bay of Biscay and the Atlantic coast to Cádiz in southern Spain. Next year, the expedition will continue to the Mediterranean.

Expedition field technician Thomas Haize is getting ready to take a sediment core from the bottom of Hästdammsviken at Askö. Photo: Michaela Lundell

Biodiversity and environmental status

In total, there will be some 30 stops along Europe's coasts to sample at more than 120 land-sea transects. The samples are then used for a variety of analyses, both of biodiversity, in particular at the microbial level, and of various environmental parameters affecting the coastal ecosystems. By analysing the presence of different molecules, researchers will be able to see what processes are taking place in the ecosystems.

In addition to samples for sequencing all DNA and identifying species by microscopy, samples are collected to analyse the amount of chlorophyll and organic carbon, and the presence of various organic pollutants and metals. For the shallow water samples alone, 18 different protocols are followed to obtain samples for different analyses, each of which can reveal specific aspects of the ecosystem.

Omics

One of the methods used is meta-barcoding, which means identifying all the species present in a soil or water sample by analysing all the DNA in the sample, looking for short genetic markers from the genome of different organisms. It includes both DNA from whole small organisms present in the sample, and from larger organisms that have left traces at the site.

Michelle Verstraaten, MSc in biology from Stockholm University, sample the soil in the forest right next to Hästdammsviken at Askö. She is one of the local volunteers organised by the research community network of Sweden for Aquatic Microbiology AMRI, assisting the expedition during its stop in the Swedish part of the Baltic Sea. Photo: Michaela Lundell

Lucas Ustick, postdoc fellow of the TREC Expedition (left) is assisted by the expedition volunteer Rickard Stenow, PhD student in marine sciences from University of Gothenburg, to carefully remove the filter from the aerosol collecting instrument and put it into a cryobag without contaminating it. Photo: Michaela Lundell

The technology is developing rapidly and it is now possible to map biodiversity on a large scale from samples taken in the wild. The TREC Expedition is largely an omics project, where omics is a collective term for several recently developed methods to study DNA, RNA, proteins and metabolites (substances formed during an organism's metabolism).

Mobile laboratories

It is a demanding logistic task to get all researchers, technicians and equipment to the different sampling locations and then prepare, store and send all the hundreds of samples from each site to advanced laboratories for analysis. The expedition scientists travel in vans that they have converted into small field laboratories, with filters, pumps, ovens, refrigerators and freezers to prepare and store the samples. In parallel, the boat Tara sails along the coast and samples the sea at deeper waters.

The expedition scientists have set up small laboratories in the vans they travel with. These mobile laboratories are used to prepare and store the many samples before they are sent to more advanced laboratories for analysis. Field Expedition Scientist Elisa Merz is filtering all of today’s seawater samples. Photo: Michaela Lundell

At Askö, the head of Askö Laboratory Eva Lindell and the Stockholm University Baltic Sea Centre's scientific leader Christoph Humborg help with all the practicalities and to select suitable sampling sites.

Today’s samples will be taken in Hästdammsviken on the eastern side of Askö. All the equipment is loaded onto the trailer of a four-wheeler and driven as close as possible, then carried by hand and on small trailers out to the reeds in the bay and into the neighbouring forest. The sea team puts on waders or dry suits, while the land team starts by installing a vacuum pump and a particle counter for the air samples.

A long day of sampling lies ahead, and the researchers are grateful for the absence of tides in the Baltic Sea, which complicate sampling along other parts of Europe's coasts.

Loading and reloading is an important part of the everyday life of the expedition. All material needed for today’s sampling of land, sea and air has been transported with the help of a four-wheeler to Hästdammsviken on Askö’s east coast. Photo: Michaela Lundell

Kerstin Leberecht and Thomas Haize lay out the transect for the sediment and water samples, while Elisa Merz takes a note of the GPS coordinates of the transect. Photo: Michaela Lundell

Coastal ecosystem health

– The TREC Expedition provides baseline data on the health status of various types of coastal ecosystems across Europe. That is of great interest to us at the Baltic Sea Centre in our climate research, where we investigate the carbon sequestration capacity of different coastal ecosystems. The expedition will provide baseline data both from here and many other coasts around Europe that we can compare with our own data, says Professor Christoph Humborg.

Text: Michaela Lundell

Read more about the TREC expedition here.