[LUM#13] The Sea Without Humans

[LUM Magazine] - Published on July 10, 2020 in Science-Society

What happens at sea when humans are driven away from the coastline? A unique mission, led by researchers from the Marine Biodiversity, Exploitation and Conservation Laboratory (MARBEC / University of Montpellier, IRD, CNRS, Ifremer), aims to assess the return of marine wildlife during lockdown.

Not a boat in sight. Deserted beaches. No one at sea. No one except David Mouillot and Julie Deter's team with their researchers, technicians, and divers. "We experienced scenes that were like something out of a science fiction movie, like the end of the world. The coastline was completely empty, something we had never seen before," says the marine biologist. This team is one of the few lucky ones who were able to crisscross the Mediterranean during this very unusual period of lockdown. Their goal: to study marine biodiversity in the absence of any human activity.

Reference state

"It was a tremendous opportunity to obtain a true baseline of the marine environment temporarily preserved from human presence. This baseline will make it possible to measure more accurately the state of degradation of marine biodiversity and the effect of the protections put in place." Before this period of lockdown, only reserves provided a glimpse of what the sea is like without humans. "A very approximate glimpse, because as we have already shown, only the few reserves located far from humans are sufficiently untouched; the others offer only a pale reflection of what biodiversity would be like in the absence of human presence," emphasizes David Mouillot.

In partnership with Andromède Océanologie and SpyGen, two companies with close ties to UM and MARBEC, funding from the Water Agency, and the green light from the maritime prefecture, a dozen scientists embarked on a unique observation campaign lasting a month and a half. "Thanks also to the involvement and responsiveness of the University of Montpellier and our laboratory, which supported us in this ambitious project." 

A bold project

Once at sea, the team deployed several types of tools to understand marine diversity. "Visual tools, on the one hand, thanks to underwater divers who filmed some exceptional images." The researchers also used hydrophones to listen to the sounds of the sea. "Normally, these recordings are disrupted by human noise such as boat engines," explains David Mouillot.

The expedition finally used an innovative tool deployed with the company SpyGen: environmental DNA analysis. The principle: filtering water samples to recover DNA left behind by living organisms. This DNA is then compared with a reference database to determine which species the DNA belongs to. " This technique reveals the presence of rare or elusive species that are never seen when diving," explains the researcher. "This will enable us to determine whether species that are usually found at the bottom or offshore have moved closer during lockdown; we should be able to detect changes in behavior."

Exceptional images

This inventory had already been carried out by the same team in the Mediterranean in the spring of 2018 and 2019, at a time when lockdown was still the stuff of science fiction. "What luck! We will now be able to make a real comparison of the state of marine biodiversity during the same period with and without human activity."

Although we will have to wait a while for the results of the environmental DNA analyses, the mission has already revealed that the Mediterranean has benefited greatly from the absence of humans. This is evidenced by this shark, the angel shark (Squatina squatina), swimming peacefully in front of diver Laurent Ballesta's camera. "A species that hadn't been seen in the western Mediterranean for years!"enthuses David Mouillot. These initial results already speak volumes about the impact of human activities. "Fishing, boating, but also simply swimming—all these activities have consequences for the inhabitants of the coastline, who have surely come out of lockdown during our lockdown."

Keywords: COVID-19, Environment, LUM#13, LUM Magazine, Research