Jellyfish of the Chesapeake
Jellyfish capture our imagination. Slow and graceful, they pulse out a beat as steady and rhythmic as our own heart. Jetting, then slowly drifting, their movement transfixes and captivates those who watch.
That is… from afar, of course. Get a little closer and that awe may turn to fear. The painful sting of the sea nettle, the Chesapeake Bay villain that we all love to hate, sends many a swimmer fleeing a leisurely swim.
Jellyfish are not fish — they are relatives of corals and sea anemones. Lacking a head, skeleton, and special organs for breathing, digestion, or excretion, jellyfish are one of the most primitive animals on earth.
During a day on the Bay, you might encounter four different gelatinous creatures — three are jellyfish, the fourth (comb jelly) a distant cousin that is often mistaken for one.
The sea nettle holds the title of the most notorious jellyfish in the Chesapeake Bay. Found from Cape Cod to the Gulf of Mexico to the Caribbean, this jelly is more plentiful in the Chesapeake than anywhere else. Unusual in its ability to thrive in water of low salinity (salt content), sea nettles have little competition in the Chesapeake. In fact, they eat one of their only competitors — comb jellies, translucent, gelatinous creatures who despite their name are not in fact jellyfish. Nettles also eat significant amounts of zooplankton, helping to improve water clarity in the Bay.
The sea nettle occurs most abundantly in the summer in the middle Bay, where it has a milky white color. In the lower Bay, sea nettles often have red markings on their long, central tentacles and on their swimming bells. The bell of some sea nettles can be as large as a generous soup bowl and their tentacles can be five or six feet long.
Sea nettles reproduce prolifically in summer months. They begin producing eggs when the nettle is only about one-and-one half inches in diameter. By the time the jelly’s swimming bell is four inches wide it sheds 40,000 eggs into the water daily.
Sir Arthur Conan Doyle made the lion’s mane jellyfish famous when he featured it as the killer in the Sherlock Holmes mystery “The Adventure of the Lion’s Mane.” Though the sting of these large, colorful jellies is potentially deadly to humans, few fatalities have actually been reported. In colder months lion’s mane jellyfish can be found in the Chesapeake Bay, earning them the nickname, “winter jellies.” The largest specimens are generally found in arctic waters, where their tentacles can be more than 100 feet long.
While the lion’s mane frequents the Bay in the winter, the moon jelly appears during Chesapeake summers. Resembling a flattened disk, its large, translucent bell can reach 10-12 inches, while its tentacles are thin and short. Although effective at stunning prey such as mollusks and plankton, the moon jelly’s sting is mild and unthreatening to humans.
Comb jellies are not jellyfish at all. They are only distantly related, but are often confused as such. Comb jellies are ctenophores (pronounced “teen-o-four”) — a group of animals defined by their bristly rows of hair-like cilia, called ctenes, which comes from the Greek word “ctena,” meaning comb-bearer. Comb jellies do not sting and are nearly transparent. Most people rarely notice them except at night, when they glow (or bioluminesce) if disturbed.
Ctenophores are voracious filter feeders, consuming large quantities of zooplankton. They play an important role in the Bay’s food web when their population is not kept in check by the sea nettle, consuming huge amounts of oyster and other fish larvae. Two ctenophore species can be found in the Chesapeake Bay, the sea walnut, Mnemiopsis leidyi, and the pink comb jelly, Beroe ovata.
More on comb jellies at:
Chesapeake Bay Program field guide, comb jellies
University of Washington, scientists Claudia E. Mills, ctenophores
Avoiding and Treating Stings
As many who swim in the Bay can testify, the sea nettle’s sting is extremely unpleasant. The intense, burning pain — like a sunburn or a bee sting — is caused when you brush against a tentacle and millions of microscopic cells called “nematocysts” inject toxins into your skin.
Some jellyfish have toxins that are very dangerous to humans. A sting from the infamous sea wasp, a box jellyfish common near Australia, can kill in as little as three minutes. Fortunately, the sea nettle’s sting is merely annoying and painful, not deadly. And there are things you can do to protect yourself. When you swim, wear a thin lycra “swim skin,” a layer of pantyhose, or even a thick coating of petroleum jelly to prevent jellyfish tentacles from touching you.
If you are stung, following these steps may help the pain and swelling subside quickly:
• Check your skin for any remaining bits of tentacle.
• If you see tentacles, pour alcohol or sprinkle baby powder on the areas to neutralize the stinging cells. Otherwise you could make the irritation worse.
• After all tentacles have been removed, apply vinegar or meat tenderizer (made into a paste) to the area, or use fresh papaya
Dangerous allergic reactions to sea nettle stings are rare, but in such cases immediate emergency medical care is necessary.
NOAA Coastwatch: Mapping Sea Nettles in the Chesapeake Bay
Maryland Sea Grant Marine Notes
TheChesapeakeBay.com Jellyfish Facts
The University of California Museum of Paleontology