The ship designed by the explorer Jean-Louis Etienne left its home port to the sound of the bagad and to the applause of a large crowd, who came to cheer these researchers-navigators.

"The beauty of this expedition is that we don't know what we're going to find," smiles Colomban de Vargas, scientific director of the mission, leaning on the deck of the laboratory boat.

According to him, it is a question of studying "invisible biodiversity at the land-sea interface and on a European scale" in order to "complete the great fresco of the ocean" begun fifteen years ago by Tara.

During its previous expeditions, the scientific schooner has already taken hundreds of samples of marine microorganisms (viruses, bacteria, prostites, animals, etc.), mainly on the high seas. She was less interested in coastal ecosystems, "which are very different and very rich," adds the researcher.

The scientific schooner Tara leaves the port of Lorient for a journey of more than 25,000 km to better understand the impact of human pollution on the invisible world of the ocean, April 2, 2023 © LOIC VENANCE / AFP

The originality of this journey, passing through the Atlantic, the English Channel, the North Sea, the Baltic and the Mediterranean, also lies in the fact that it is part of a larger mission called TREC ("Crossing European Coasts").

A mission that will mobilize several hundred researchers until July 2024, under the aegis of the European laboratory EMBL (European Molecular Biology Laboratory), a kind of CERN of biology, based in Heidelberg, Germany.

Because, beyond the exploration of biodiversity, it will also be a question of studying how pollutants (pesticides, drugs, chemicals, etc.) interact with invisible biodiversity.

"One of the objectives is to map the different pollutants in coastal waters, and to look at how this influences microbial diversity," explains Flora Vincent, laboratory director at EMBL.

"Monumental"

On imaginary lines along Europe's coasts, researchers will carry out systematic sampling from land to sea: in soil, in sediments, on marine and terrestrial aerosols, in coastal waters and at sea. The mission will include 120 coastal sampling sites in 46 regions of 22 European countries between 2023 and 2024.

"We know that at very low doses, we observe very large effects on the ability of organisms to grow, divide, survive," notes Flora Vincent. "So in a field, a molecule that blocks photosynthesis is going to be used to prevent weeds from growing. Sometimes these chemical molecules will also impact microalgae, which produce 50% of oxygen each year."

EMBL researchers will follow Tara's journey ashore, with vans transformed into mini-laboratories, but also a semi-trailer carrying scientific research tools (microscopes, high-pressure freezer).

The scientific schooner Tara leaves the port of Lorient for a journey of more than 25,000 km to better understand the impact of human pollution on the invisible world of the ocean, April 2, 2023 © LOIC VENANCE / AFP

In terms of resources, "it's monumental," says Flora Vincent. EMBL researchers are rather reputed to be "laboratory rats" but "there is a real awareness of the need to go and see what is happening in the natural environment," says the researcher specializing in environmental research.

During the presentation of the mission in March, Edith Heard, the director general of the EMBL, compared the expedition to that led in the nineteenth century by Charles Darwin, father of the theory of evolution, on the ship Beagle. "I think it will give rise to a lot of discoveries" or even "maybe even new theories," said the scientist.

During her last expedition, completed in mid-October 2022, Tara had traveled 70,000 km around the globe for nearly two years, taking thousands of samples of microorganisms whose analysis should allow a better understanding of the functioning of ocean plankton.

© 2023 AFP