The sea without men

Not a boat in sight. Deserted beaches. No one at sea. Nobody except the team of Julie Deter and David Mouillot* with their researchers, technicians and divers. They are among who were able to sail the Mediterranean during this very special period of confinement. Their objective: to study marine biodiversity in the absence of man.

photos © Lila Desgarnier / Nadia Faure / Lola Romant / Raphaël Seguin

"It was a fantastic opportunity to obtain a true reference of the marine environment temporarily preserved from human presence. In particular, this new reference will enable us to measure more precisely the state of degradation of marine biodiversity and the effect of the protections put in place," explains David Mouillot.

The team deployed several types of tools to understand marine diversity. " Visual tools on the one hand, thanks to the underwater divers who filmed some exceptional images. But also hydrophones to listen to the sounds of the sea, which are normally interfered with by boat noise.

Finally, the project used an innovative tool: environmental DNA analysis. The principle: filter water samples to recover the DNA left behind by living organisms. This DNA is then compared with a reference database to determine which species the DNA relates to. This technique can reveal the presence of rare or stealthy species that are never seen underwater," explains David Mouillot. So we can find out whether species usually found on the seabed or offshore have moved closer together during confinement."

The researchers observed a Mediterranean that benefited greatly from the absence of man. "Fishing, pleasure boating, and even just swimming - all these activities have consequences for the coastal inhabitants, who have surely deconfined during our confinement. And vice versa this summer.

* Laboratoire Biodiversité marine, exploitation et conservation (MARBEC)(IRD, Ifremer, Université de Montpellier, CNRS) - Andromède Océanologie. Mission carried out in partnership with SpyGen, with funding from the Agence de l'Eau, and the green light from the Préfecture Maritime.

Photos © Lila Desgarnier / Nadia Faure / Lola Romant / Raphaël Seguin