[LUM#13] The Sea Without People
What happens at sea when humans are kept away from the coast? A unique study, 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 single boat in sight. Deserted beaches. No one at sea. No one except David Mouillot and Julie Deter’s team, along with their researchers, technicians, and divers.“We witnessed scenes straight out of a movie—like the end of the world. The coastline was completely empty—it was something we’d never seen before,” says the marine biologist. This team is among the select few who were able to traverse the Mediterranean during this very unusual period of lockdown. Their goal: to study marine biodiversity in the absence of any human activity.
Baseline
“This was a tremendous opportunity to establish a true baseline for the marine environment temporarily spared from human presence. This baseline will, in particular, allow us to more accurately measure the extent of marine biodiversity loss and the impact of the protective measures put in place.” Before this lockdown, only marine reserves provided a glimpse of what the sea is like without humans.“A very rough idea, because as we’ve already shown, only the few reserves located far from human activity 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—along with funding from the Water Agency and approval from the Maritime Prefecture, a team of about ten scientists set sail for a month and a half on a unique observation campaign.“Thanks also to the commitment 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 study marine biodiversity.“Visual tools, for one, thanks to the scuba divers who captured exceptional footage.” 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 also utilized an innovative tool developed in collaboration with SpyGen: environmental DNA analysis. The process involves filtering water samples to recover DNA left behind by living organisms. This DNA is then compared against a reference database to identify the species to which it belongs. “This technique reveals the presence of rare or elusive species that we never see while diving, ” explains the researcher. “We’ll be able to determine whether species typically found on the seafloor or offshore moved closer during lockdown; we should detect changes in behavior.”
Exceptional images
This same team had already conducted this survey in the Mediterranean in the springs of 2018 and 2019, at a time when lockdowns were still the stuff of science fiction.“What a stroke of luck! This will allow us to truly compare the state of marine biodiversity during the same period, with and without human activity.”
Although it will be some time before the results of the environmental DNA analyses are available, the expedition has already revealed a Mediterranean Sea that has clearly benefited from the absence of humans. A prime example is this shark, the angel shark (Squatina squatina), swimming peacefully beneath the camera of diver Laurent Ballesta.“A species that hadn’t been observed in the western Mediterranean for years!”exclaims David Mouillot. These initial findings already speak volumes about the impact of human activities.“Fishing, recreational boating, but also simply swimming—all these activities have consequences for the coastal inhabitants, who have surely come out of lockdown during our confinement.”
See also:
UM podcasts are now available on your favorite platform (Spotify, Deezer, Apple Podcasts, Amazon Music, etc.).