Before developing this topic of hope for humanity, let us recall that eDNA exploitation allows us to analyze the diet of a species, to inventory the biodiversity of an ecosystem, to reconstruct past biodiversity, to detect species: invasive, new, rare or threatened.

 

Indeed, DNA is the support of genetic information and the signature of living beings. Individuals leave traces of their passage in their environment: droplets of saliva, mucus, skin, scales, droppings, decaying cells... These DNA-laden remains that float in the air, move with river and Ocean currents, and are deposited on soil or in sediments are commonly referred to as environmental DNA (eDNA). Thus, like forensic detectives inspecting suspicious DNA from crime scenes, biologists extract DNA from environmental samples in order to characterize the species that live there…, or that have only transited to other sites (migratory species).

 

The first terrestrial eDNA studies date back to 2003, only twenty years ago. In France, the first use of eDNA concerned the detection of an aquatic vertebrate species, in 2007. This was to identify the bullfrog, Lithobates catesbeianus, introduced into southwest France in 1968. It is also thanks to eDNA that DNA traces of extinct animals such as the woolly mammoth (Mammuthus primigenius) and the giant moa (Dinornis robustus) were identified in sediments from Siberia and New Zealand.

 

In 2016, the initiative of Sovereign Prince Albert II of Monaco to take up the baton held out to him through several generations by His great-great-grandfather Prince Albert I of Monaco (1848 - 1922) and to relaunch a cycle of Monaco Explorations combining the Principality's driving forces: His Foundation Prince Albert II of Monaco, the Monaco Scientific Center, and the Yacht Club de Monaco, has allowed two French scientists, David Mouillot and Tony Dejean, to get together around an ambitious project.

 

"David Mouillot, professor at the University of Montpellier, a marine ecologist, had followed the work we had done in freshwater with environmental DNA" explains Tony Dejean, founder of SPYGEN. "He suggested that I accompany him on the maritime adventure of the first Monaco Explorations, aboard François Fiat's YERSIN, without really knowing at the time where it would lead us. Thanks to this initiative and the unfailing support of the Foundation Prince Albert II, we were able to carry out incredible, unthinkable work and deploy these technologies around the world. Thus, thanks to the Prince, we have been able to establish close collaborations with Colombia, where we have just set up our first environmental DNA analysis laboratory. In France, the contribution of Pierre Boissery, who believed in our very innovative approach, allowed us, thanks to funds from the Rhone Mediterranean Corsica Agency, to carry out the first very promising inventory campaigns on the French Mediterranean shores. This collaboration has also allowed us to develop genetic reference bases for fish. Because it is not enough to collect seawater samples and extract eDNA from them, it is also necessary to match each DNA sequence obtained with the name of species perfectly identified beforehand, so that the information is complete, usable and exploitable if necessary."

 

There would be multiple benefits to fisheries management using an eDNA approach: cost-effectiveness, broader geographic coverage, early detection of invasive species, stock assessment, exploration of previously inaccessible aquatic environments, discovery of new deep-sea species, etc.

 

But David Mouillot goes further: "If the study of species migration due to climate change is facilitated by the collection and study of eDNA samples, we must remember that unlike humans and terrestrial animals who release the carbon stored in their bodies upon death, fish and marine mammals sequester CO2 and then ship it to the sediment at the bottom of the Ocean, where it is stored for millennia. Our "Blue Carbone" project aims to implement ecological solutions to maintain fish stocks, to contribute to the fertilization of the Ocean and to rehabilitate its natural function as a carbon pump. In this approach, artificial intelligence is a tool that we use more and more frequently and successfully in the MARBEC laboratory".

 

On his side, Tony Dejean, who lives in Bourget-du-Lac (France), far from the sea but close to rivers and lakes, has long wondered how to increase his databases and make them available to the widest possible range of potential users concerned with the management of natural resources, in particular by developing Vigilife – The Global Life Obserbatory: "What would be the best solution to collect eDNA from as many oceanic sites as possible to better understand the species present? The idea came to me to arm a fleet of 15-20 meters cruising catamarans. They could move at low cost on the Ocean without CO2 emission to collect a maximum of information in a minimum of time on a multitude of sites. It remains to be verified in reality the relevance and scientific efficiency of such a device...".

 

"Contributing to the development of eDNA marine sample collection and analysis procedures, by David Mouillot and his team at MARBEC on the one hand, and by Tony Dejean and his collaborators from SPYGEN and Vigilife on the other hand, is part of our desire to do what I call the "Science of Use" as opposed to the "Science of Observation", comments Yvan Griboval, President of OceanoScientific and Director of the eponymous expeditions. "Thanks to these methods, it seems to me possible to direct fishermen - coastal fishermen at first - towards sites that are not very frequented because of the habit, sometimes transmitted from father to son, of systematically fishing on the same sites ... complaining that the resource is decreasing. And for good reason, they only fish there! Thanks to the use of the information generated by the eDNA study, it would be possible to encourage fishermen to change their habits, to prospect new sites and, thus, to allow the resource to naturally recover on overfished sites, so that their fishing actions become virtuous and sustainable. Nature would gain. The fisherman too. As for the consumer, he would have the guarantee of a quality fish in his plate".

 

Another essential use for the fishery, the sentinel role of invasive species using eDNA, motivated by the need for early detection of these species before they can become established, spread and cause irreversible ecological and economic impacts. 

 

Talk to the fishermen in South Finistère (France). They are currently seeing their scallop fishing objectives on the Glénan site, which is rather profitable, ruined by the presence of octopuses (Le Marin & Ouest-France, 23 November 2022). Yes, an invasion of octopuses in Brittany (France) ! The same ones that holidaymakers love to eat in summer on the terraces of the beaches of the French Riviera with a chilled Provence rosé. Did you say climate change?...