• Like a Waze, everyone can record the presence of jellyfish on the observation portal developed by a company from Sophia Antipolis, which then crosses this data with satellite observations.

  • According to Antoine Troullier, engineer at Acri-ST, these purple jellyfish can be observed in summer and winter, and like cold water.

    Their presence is therefore mainly linked to the southerly wind which brings them back to the coast.

Last weekend, the jellyfish observation site in the Mediterranean experienced a peak of 10,000 visits per day.

Bathers on the lookout for green, orange and red pictograms showing the presence (or absence) of jellyfish on the beaches.

"This interactive map works like a Waze, it is accessible to everyone and all you have to do is register to make a statement", explains Antoine Troullier, engineer at Acri-ST.

This company, based in Sophia Antipolis, specializes in the processing and archiving of earth observation satellite data.

It launched this observation portal a dozen years ago, as part of a participatory science project.

There are many jokers who report jellyfish at the top of the Sainte Victoire mountain, but their contribution is quickly removed from the system, and on the whole the contributors play the game well. Most concern the stretch of coast between Menton and Marseille .

“Everyone benefits from being informed,” continues Antoine Troullier.

As for users, a bath without jellyfish: but be careful to trust the green pictogram, the only guarantee that there are no creatures (the absence of a pictogram is not a sufficient indicator).

For its part, Acri-ST is developing a valuable database on jellyfish, which it can make available to researchers.

“With each observation of jellyfish, indicates Antoine Troullier, we associate environmental data that we recover via satellite, on the temperature of the air, the sea, the currents, the winds.

»

"I'm going to bust a myth"

"Right now, we have a hundred sightings a day, but quite simply because there are more people going to the water's edge," he adds.

They are less noticeable in winter but they can be just as numerous.

I saw the purple sea in February, not to get into the water in wetsuit!

Along the way, he smashes a few ideas that he thinks are received: “I'm going to bust a myth, these jellyfish like deep, cold water.

Their proliferation is not linked to climate change, even if it plays a role on their predators, but more to the weather.

We are not on the same time scale.

»

To listen to it, it is thus necessary to watch for the south wind.

"These purple jellyfish migrate at night to hunt for plankton, and when there's a southerly wind system, they're caught and brought back to shore, where they die within a day or two.

As long as the wind phenomenon lasts, it will continue like this, with new jellyfish replacing them, they are not the same.

Conversely, the Mistral will chase jellyfish offshore.

With the Estérel which stops this wind at Saint-Tropez, jellyfish are observed more on the side of Antibes and Cannes.

“Clearly, there are more in the Alpes-Maritimes than in the Var or the Bouches-du-Rhône”, estimates Antoine Troullier.

Planet

Hypnotic 'ghost jellyfish' spotted in the depths of the Pacific Ocean

Planet

Côte d'Azur: Proliferation of one species, appearance of another… Why do we have the impression of being invaded by jellyfish?

  • Company

  • jellyfish

  • Mediterranean

  • Sea

  • Geolocation

  • Marseilles

  • Paca

  • Nice