Mauve stinger jellyfish sting more than 200 swimmers at Robert Moses and Jones Beach

Thousands of mauve stinger jellyfish — which inflict a painful sting and are more likely to be seen off the coast of a Mediterranean beach town than the waters near Fire Island — were spotted off Long Island this weekend.

About 200 beachgoers at Robert Moses State Park and 30 at Jones Beach State Park visited first aid stations to treat stings from the purplish invertebrate on Sunday, said George Gorman, Long Island regional director for state parks.

“We literally had thousands along the shoreline here at Robert Moses State Park,” Gorman said during an interview Monday on the beach. “They were right here so the people were interacting with them and they got stung.”

It seems the mauve stingers, which are also bioluminescent and are sometimes called purple-striped jellies, left as quickly as they came. They appeared to move farther out to sea the next day and comparatively no one had sought help for a sting by early afternoon on Labor Day, Gorman said.

Gorman speculated that many more people were stung this weekend but did not seek help.

“If it was a mild sting they wouldn’t have come to the first aid station,” he said.

Mauve, as well as the more common lion's mane jelly, also have been spotted off Fire Island, officials said.

On Sunday, Fire Island Ocean District beaches displayed purple flags in the lifeguard areas and red flags in the bathing area as part of Islip Town’s dangerous marine life protocol, according to town spokeswoman Caroline Smith. A “light amount” of mauve jellyfish were again spotted in the water Monday, she said.

Usually far from shore

Paul Bologna, director of the marine biology and coastal sciences program at Montclair State University in Montclair, New Jersey, said mauve stingers are native to the region, but typically dwell in deep water far from shore. They are more commonly seen in the Mediterranean Sea and the Gulf of Mexico than the tristate area.

The theory is that they rose with an upwelling of water and were brought closer to the surface here by the tides and coastal currents, Bologna said.

“I have found a few isolated [mauve stingers] over a decade of working with jellyfish in the mid-Atlantic region,” Bologna said. “This is an extremely rare event.”

The more common types spotted in the region are the rhacastoma, the moon jellyfish and the lion’s mane, he said.

Bologna moderates the New Jersey Jellyspotters Facebook page, where members in the past week have posted photos of mauve stingers and the nasty welts they left on their arms and legs. Similar to Long Island, the sightings and stings were contained to a short window of time.

“Here there were just lots and lots of reports of people being stung all over the place,” he said. “And then you come back the following week, and they're kind of gone.”

There’s never been a report of a fatal mauve stinger attack, Bologna said.

Beachgoers at Robert Moses on Monday did their best to avoid interaction, although the threat did not keep many out of the water.

“First the sharks, now the jellyfish,” said Carol Ying, 48, of Dix Hills, referring to an unusual spate of local shark encounters this summer. Still, she was happy to put down her beach read for a dip in the Atlantic Ocean. “I love the water. It’s their domain. You have to expect something in there.”

By Vera Chinese

vera.chinese@newsday.com@VeraChinese

Vera Chinese covers Suffolk County government and politics. She joined Newsday in 2017 after working as an editor for the East End lifestyle publication northforker and a general assignment reporter for the New York Daily News.