Reports of astonished walkers or stung swimmers have multiplied since the beginning of June. And do not weaken. A very large number of jellyfish has been observed on the Atlantic coast for about twenty days. There are sometimes hundreds of them on the same beach. The sightings stretch from the Basque Country to the English Channel, reports theIfremer, but they now focus on Morbihan, Loire-Atlantique and Vendée. “In fact, a lot of people came forward. However, there is nothing abnormal in this season, there are still a lot of jellyfish in June”, assures Elvire Antajan, zooplankton ecology researcher for Ifremer.
The more massive than usual presence of these gelatinous marine animals is, however, explained by the direction of the prevailing winds (north and northwest winds). “Jellyfish are very sensitive to the surface current and this pushes them towards our coasts, which results in significant strandings in places,” says Evire Antajan. The good weather also caused a peak in witnesses on the beaches in June. “As the beaches are very crowded, more people are aware of the presence of jellyfish. Usually, they are there but are less noticeable. »
The compass jellyfish, better to avoid it
The researcher, who thinks that the phenomenon should “fade in a few days”, also hypothesizes the rise in water temperature, in particular in the Bay of Biscay, due to a very late spring. sunshine and, more generally, to global warming. “Plankton grow faster in these conditions and that would benefit jellyfish. However, it is difficult to be certain on this point because there is no monitoring data on jellyfish in France. We mainly work on fragmentary observations,” reports Elvire Antajan. Other potentially favorable avenues for jellyfish are being studied by Ifremer, such as the consequences of overfishing or the installation of wind farms at sea.
Three species of jellyfish are currently recorded on the Atlantic coast. The most common would be chrysaora hysoscella, also nicknamed compass jellyfish or compass jellyfish. “She is beamed with a brown frieze. It can measure up to 20 cm. If you see any, you better get out of the water. It is indeed a rather stinging species, even on the sand. There is also the jellyfish Aurélie (aurelia aurita), slightly bluish, which “looks like an umbrella with four horseshoe shapes”. Being able to measure up to 40 cm, it is not very stinging. The so-called “cauliflower” jellyfish (rhizostoma octopus), translucent and spectacular as it can measure up to one meter in diameter, has also been reported. It is generally harmless to humans. A fourth species, the cyanea lamarkiistinging, is also visible in the English Channel and the North Sea.
Do not rinse with fresh water… or urine
“In the presence of a stranding of jellyfish, it is recommended to move away and warn the first aid station, advises Elvire Antajan. If you are stung, you must rinse the wound with sea water. Especially not with fresh water, at the risk of bursting the stinging cells. If filaments remain attached to the skin, you can scrape off a little with sand or an object, a credit card for example. » If the pain persists, consult a pharmacist or even a doctor. Useless, on the other hand, to urinate on the wound, as a received idea suggests it. ” It’s no use. There is even a risk of superinfection. »
Mobile applications and participatory websites allow you to report the presence of jellyfish and consult a map. This is the case of jellywatch, Jellyfish alert or Jellyfish. “These are interesting indicators. There is, however, no scientific validity behind it. We are also thinking, on the Ifremer side, of proposing an application of this type. »