Green Guru: How Poisonous are Jellyfish?

As temperatures climb, refreshing salt water beckons. But when you take the plunge into the ocean's cooling surroundings, don't forget about the translucent creatures--which are critical to the marine ecosystem--swimming nearby. To find out just how poisonous they might be, read the Green Guru's response to a reader's question.

Are all jellyfish poisonous? What should I do if I get stung by one?
—Jane McMahon, Fort Lauderdale, FL

Those gelatinous, undulating creatures we call jellyfish all produce at least some toxin, but not every species is dangerous to humans.

There are a couple thousand varieties worldwide, from small sea nettles to large moon jellies, and the severity of their stings varies. A handful are deadly.

Some of the most dangerous are box jellyfish, which have 10-foot tentacles and the planet’s most potent venom. (They are found mostly in waters off the coast of Australia.) By contrast, others, like cannonball jellies—tennis- to soccer-ball sized blobs that have a reddish-brown pattern and live primarily in the Gulf of Mexico—don’t usually affect humans.

No matter the size or toxicity, jellyfish are crucial to ocean health. “In spite of the fact that when their numbers are high they’re often considered a nuisance, in many areas they’re actually an important part of the natural ecosystem,” says Denise Breitburg, a scientist at the Smithsonian Estuarine Research Center. They use their venom to kill or paralyze prey—usually zooplankton and small fish—and help to keep those populations in check.

If a jellyfish stings you, get out of the water and ever so carefully remove the tentacles with a towel or sand (or anything other than your hand, to prevent further stinging). Contrary to popular belief, peeing on the area won’t relieve the burn. Instead, try to soothe the pain with vinegar or a paste made of baking soda, and see a doctor if you feel sick. The next time you hit the waves, take the sting out of your day at the beach by appreciating those translucent swimmers from a distance.

“The views expressed in user comments do not reflect the views of Audubon. Audubon does not participate in political campaigns, nor do we support or oppose candidates.”