Thousands of jellyfish that can deliver a painful sting have been spotted in two Charlestown salt ponds, according to the state Department of Environmental Management.
The state departments of Health and Environmental Management delivered a joint statement Wednesday advising swimmers that Atlantic sea nettle jellyfish “have been identified in high numbers by DEM’s Division of Marine Fisheries in Ninigret and Green Hill Ponds.”
“Their stings typically cause moderate discomfort and itchy welts,” the departments say in a press release.
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“Their population in the ponds has been exploding over the last month or so, probably as water temperatures have increased, and last week we observed thousands of them in the western section of Ninigret Pond along the East Beach side,” said Katie Rodrigue, principal marine biologist in the DEM’s Division of Marine Fisheries.
Sea nettles can often be found in Rhode Island waters during the summer, most commonly in South County salt ponds, the state says.
People using the ponds should bring a first-aid kit, with a bottle of vinegar and sting spray, the state says.
Anyone who is stung should remove visible tentacles with a gloved hand or a plastic bag
The area should be rinsed in vinegar, a sting spray or salt water, according to the state. Don’t use fresh water because that can make it worse.
The DEM doesn’t know why there are so many of the jellyfish this summer but says the numbers are likely to decline over the summer.
Jellfyish expert Paul Bologna says that sea nettle numbers tend to fluctuate from year to year. But the species tends to do better in areas with more docks, jetties and other manmade structures to which its polyps can attach before producing free-swimming jellyfish. In undeveloped waters, they will attach to oyster shells.
Bologna, director of the Marine Biology and Coastal Sciences Program at Montclair State University in New Jersey, said that sea nettle numbers in his state declined after Superstorm Sandy in 2012 washed away coastal structures.
“We’re just starting to get back to the numbers we had in 2011 and before, which were really big years,” he said.
It can take time for sea nettle numbers to build, but when they get to a certain point, the population can explode. That’s because the polyps can clone themselves, spreading over a larger area before budding off jellies.
Bologna is working with coastal residents in New Jersey to pull docks out of the water in the off-season and power-wash them to remove them of sea nettle polyps.
“We’re never going to get rid of them, but if we disrupt that, there will be fewer,” he said.
— With reports from Journal Staff Writer Alex Kuffner
On Twitter: @jgregoryperry