On warm summer days, bathers may be surprised by jellyfish washed ashore. One every few meters, or, as happened last weekend on Vlieland, hundreds at once. What should you do as a beachgoer? And is the jellyfish doing okay?
The answer to the latter is a resounding yes, says biologist and Ecomare curator Pierre Bonnet. The many jellyfish on Vlieland were disk jellyfish, also known as barrel jellyfish or cauliflower jellyfish. “They are completely harmless to humans. If you want, you can just pick them up and put them on your head.”
They do have stinging cells, with which jellyfish can cause damage. But these are not strong enough to penetrate human skin.
In the North Sea, along the Dutch coast, you are most likely to encounter these four species: the moon jellyfish, lion’s mane jellyfish, compass jellyfish, and barrel jellyfish. The moon jellyfish and the barrel jellyfish are completely harmless to humans.
“The compass jellyfish and lion’s mane jellyfish can sting,” says Bonnet. “You don’t have to be a biologist to see which jellyfish can be harmful. If the jellyfish has lobes – thumb-thick, slimy blobs – then they don’t shoot stinging cells. If they have long, thin tentacles, then you have to be careful.”
Stinging Cells
Many jellyfish have tentacles full of small stinging cells. These contain a harpoon with poison. When you touch the jellyfish, that harpoon shoots out and pricks your skin.
The poison causes pain, itching, or in the worst case, blisters. Each cell can only shoot once. After that, it is ’empty’ and the jellyfish has to make a new one.
Don’t Immediately Jump Out of the Water
A ‘bite’ from a lion’s mane jellyfish is annoying, says Bonnet. But according to him, it’s not something to worry too much about. The effect can vary from some redness to, in severe cases for people who are very sensitive, a blister.
“As a biologist, I swim a lot in the sea and sometimes get stung by a lion’s mane jellyfish. I’m not worried. After 200 meters of swimming, the pain is gone, and once ashore, there are not even any red streaks to be seen,” says Bonnet.
“The sting is neutralized by the seawater. People who get stung often jump out as quickly as possible. But it’s best to stay swimming for another fifteen minutes.”
This is what you do after a jellyfish sting
In the event of a jellyfish sting, urinating on the wound is a myth, says dermatologist Patrick Kemperman. This only activates the stinging cells and makes the pain worse. Here’s what you can do:
Eating Washed-Up Jellyfish is Not Recommended
Leave the jellyfish you see on the beach alone, to be sure, both biologists say. “They are probably harmless. Before they actually wash up on the beach, they have already been tossed over the bottom by the waves for a long time and they have lost their stinging cells,” says Bonnet. “After an hour, you can touch the most dangerous jellyfish. I once held a Portuguese man-of-war in my hands.”
All those dead jellyfish on the beach have something ominous about them, but it’s quite normal, Bonnet explains. “If there are many jellyfish in the sea, many also wash ashore. What you see lying on the beach is only a small part of what is swimming in the sea.”
So a beach full of dead jellyfish doesn’t say much about how the population is doing. Bonnet: “There is a lot of food in the North Sea, so there are many jellyfish. The warmth plays a role in this. The cauliflower mushrooms can continue to grow if the water stays above 4 degrees. Sometimes they live a whole winter and you come across jellyfish of 1 meter in diameter.”
Such a jellyfish on dry land is a great opportunity to take a good look at them. They are often very beautiful, says Bonnet. Eating them is not recommended, says Dekker. “When I once came across a large lion’s mane jellyfish, I couldn’t resist cutting off a piece and tasting it. It tastes like you think it tastes: watery and slippery.”