What you need to know about the hundreds of dead jellyfish on Hilton Head's beaches

It happened again this weekend. Hundreds of dead jellyfish were seen washed up on Hilton Head's beaches.

It can be a disturbing and kind of disgusting sight — hundreds of lifeless jelly figures and detached gooey limbs cluttered the shore, making it almost impossible not to step on one.

What exactly is going on in the ocean that wipes out masses of jellyfish at one time?

We reached out to a couple of experts to find out.

This happens a lot

Carlos Chacon, manager of natural history at the Coastal Discovery Museum, said the Hilton Head coast normally sees large numbers of jellyfish washing ashore during the spring and early summer. However, incidents can happen at other times of the year that cause several hundred jellyfish to appear on shore at one time.

What causes it?

Jellyfish tend to travel in groups, called blooms, and sometimes rough winds, swells and currents send them to shore at once. Cooler water temperatures also contribute to mass jellyfish deaths.

“Jellyfish are organisms that swim with the current. They often get pushed to shore as a group,” Blaine Griffen, a marine biologist at the University of South Carolina, said. “Sometimes, it’s the current, and some of them are just killed by annual population cycles.”

Jellyfish are mostly made of water, so they die quickly after washing up on shore.  They're cold-blooded animals, and can lose mobility when water temperatures are below normal.

Jellyfish can sting you after they are dead

The good news is that the most popular jellyfish in South Carolina waters is the cannonball jelly, which Chacon said is not harmful to humans, dead or alive. Some people even pick them up and play with them.

“They can be fun to play with,” he said.

Cannonball jellyfish look like mushrooms, and lose their color soon after they wash up on shore.

The bad news is that other dead jellyfish known to swim off the Carolinas can sting you when they’re dead, like the Portuguese man-of-war, which is blue or purple in color and looks like a blown-up plastic bag.

So in general, don’t touch a dead jellyfish if you don’t know what kind it is.

How can you tell if a jellyfish is dead?

In general, if the jellyfish has lost its typical round shape and is sort of flat, it is dead, Chacon said. However, if it is still round and freshly washed ashore, it might be alive.

Nature takes care of these dead jellies

Don’t worry, no one has to clean up dead jelly bodies on the beach.

“They will get eaten by seagulls, crabs and other scavengers, and whatever is left of it will eventually decompose on the beach.” Chacon said.

This story was originally published March 12, 2018 at 3:43 PM with the headline "What you need to know about the hundreds of dead jellyfish on Hilton Head's beaches."