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What are these “sea currants” that wash up on our beaches?




“Chemicals escaped from a factory?” Small jellyfish? », Asks a regular at Pendruc beach, in Fouesnant (29), by posting on Facebook the photo of a cluster of translucent, gelatinous beads. “They look like octopus eggs,” replies a user. “Baby jellyfish,” suggests another… A bather at Dourveil beach, in Névez (29), posted similar photos and wonders what these marbles are found on the sand and in the water. “Vélelles”, suggests a scholar. “Salps,” said another.

These little translucent bubbles are “sea currants”. Unlike jellyfish, they are not stinging (Marie-Morgane Lepetit)

These strange organisms have suddenly appeared in recent days on the beaches of South Finistère. We have seen them at La Torche, on the beaches of Plovan-Tréogat, Combrit, Trégunc, Fouesnant, Névez… Thousands of small bubbles, like gelatinous drops of water, measuring 1 to 3 cm.

Safe for swimming

“Ctenaries, also called ” sea currants ””, slices the National Museum of Natural History. They are therefore not jellyfish. Unlike the latter, ” currants’ ” are devoid of stinging cells and are safe for swimming. “The phenomenon is” rather ephemeral because it follows the blooms of phytoplankton “(that is to say the proliferation of plankton under the effect of sunshine and heat in particular).

What are these “sea currants” that wash up on our beaches?
The “sea currants” washed up by the thousands on the beach of Dourveil in Névez (29) (Marie-Morgane Lepetit)

They are animals that live in open water and which, unlike plankton, are able to move thanks to their tiny filaments.

For a few days (“the end of last week”), Nathalie Delliou, from Esprit Nat’ure, is bombarded with questions about these arrivals. The naturalist, specialist in the marine environment, explains to us what these “sea currants” are, Pleurobrachia pileus of their scientific name. “These are nectons, animals that live in open water and which, unlike plankton, are able to move thanks to their tiny filaments. “

A natural phenomenon

The “sea currants” “live in schools”, and can form very large groups “to the point that by their biomass, they can for example block turbines. “They are” carnivorous animals, which catch their prey, mainly plankton, thanks to their small gripping tentacles. “But for us,” they are perfectly harmless, “said Nathalie Delliou.

This is something that we have known for a long time. It’s part of aquatic life

As the velelles, salps (which resemble “sea currants” but are much larger) or physalies, “sea currants” sometimes run aground, over the currents, in large quantities on European beaches. Don’t panic, it’s completely natural. “It’s something we’ve known for a long time. They are often observed in the open sea. It is part of aquatic life. “

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