Jellyfish in California

This Scary Giant Black Jellyfish Is Stinging Swimmers In Southern California

It’s got a three-foot bell and a whopping 20-foot-long body. Eeeep.


via Flickr user Ganesha.isis

Reports coming out of Orange County, in Southern California, suggest that a rare giant jellyfish, only recently discovered, is invading beaches and stinging swimmers. On July 4th, swimmers in Laguna Beach, a beach town famous as a setting for great television, came ashore with hefty stings on their bodies and dark, odd membranes sticking to them.

So what is this weird plague?

The black jellyfish (Chrysaora achlyos, also called the black sea nettle) is huge, with a bell (that’s the dome-shaped part of the body) that can reach three feet across. But it’s the rest of the body that’s so scarily big: its arms, described by the Monterey Aquarium as “lacy and pinkish” can reach 20 feet long, and its tentacles can by nearly 8 feet long. It was only officially named and described in 1997, though it can be seen in photographs as far back as 1926. (It’s clear in photographs, since it’s the only dark-colored jellyfish in that part of the Pacific Ocean.)

This jellyfish invades the coast periodically, dependent, we think, on ocean temperature (its invasions coincide with El Niño and La Niña). Human influence on the oceans may also be a factor; increased levels of organic matter, like fertilizer from farms, may attract or feed zooplankton, which the jellies follow and eat. We have no idea what it does or where it lives when it’s not washing up on the shores of wealthy Southern California beach towns, but it comes in large numbers every decade or so. It was first noticed in 1989, then in 1999, and now this year.

It eats zooplankton and sometimes other jellyfish, we think; we know hardly anything about this creature. We do know that its sting is painful but not debilitating or deadly to humans, the pain only lasting about 40 minutes and having no known lasting effects. That’s likely due to its diet; jellies that feed on larger or more complex animals like fish tend to have stronger stings. The stings of some jellyfish, like a few species of box jellyfish, can be fatal to humans. Not the black sea nettle, thankfully.

Jellyfish in California

Jellyfish are common in California, but they are not everywhere all of the time. Sometimes, in some locations, a large mass of jellyfish will “invade” the beach. Some jellyfish are harmless, others have a relatively mild sting, and some creatures look like jellyfish but really are not.

Two jellyfish in particular, the Portuguese Man of War, and the box jellyfish can give a very painful sting. Another type, comb jellies, are not true jellyfish and do not sting.

Many jellyfish have tentacles that trail down from their bodies into the water. The tentacles have stinging cells, called nematocysts, that have tiny harpoons and venom. When the tentacles touch something or are otherwise stimulated, the nematocysts build up pressure until they burst, driving the little harpoons and the venom into the unlucky victim.

Some jellyfish have very weak venom, others have extremely potent venom, which upon sufficient exposure, can result in the death of a human. Death from a jellyfish sting has only rarely, if ever, happened in Florida waters. Florida just does not have deadly jellyfish.

There is a case of three military combat divers in the Florida Keys who suffered symptoms that resemble those of a person stung by the deadly Irukandji jellyfish normally found in Pacific waters, but it is not known for certain what species stung the divers.

There are many different types of jellyfish in Florida waters, including some exotic invasive species with an unpredictable distribution.