"More than any other beings, they are true animals of the sea, their frail, diaphanous shapes symbolize the life of the ocean in a way achieved by no other form. Like pale-colored ghosts they roam the waters of the world from the frozen arctic to the warm currents of the tropics and from the shallow bays and creeks to the uttermost regions of the great deeps"- Gilbert Klingel, The Bay

The animals to which Gilbert Klingel is referring are jellyfish. They can bring scorn to the face of even the most hardened naturalist. And, unfortunately for those attracted to local waters, jellyfish thrive in the Chesapeake Bay.

There are five common types of jellyfish found in the Bay and its tributaries. Of these, only three are considered true jellyfish. The other two, the mermaids purse and the sea walnut, have no or few tentacles and cannot sting. The second group, known as comb jellies, are generally transparent but often tinged green or pink and have bands of seemingly colored cilia striping their bodies. Flapping of the cilia allows the jellies to propel themselves casually through the water. The most distinctive characteristic of the sea walnut is its ability to luminesce, emitting a green glow, when disturbed.

The other three types of jellyfish do not have such innocuous traits as the comb jellies. These jellyfish, the lion's mane, moon jellyfish, and sea nettle, all have tentacles loaded with stinging cells. The lion's mane floats through Bay waters only during the winter and early spring and is not a hinderance to normal recreational activities. The moon jelly is the Bay's largest species but its sting is generally mild. It is characterized by fringe-like tentacles and clover-shaped red gonads.

The sea nettle likely receives the dubious distinction as the least welcome creature inhabiting Bay waters. It's peak in abundance corresponds precisely with the period of greatest recreational use of the Bay. Once sea nettles have spread throughout the tributaries and into the Bay, swimming generally slows considerably or ceases for the remainder of the season. For those who do venture into the water, the nettle's sting is usually painful and can cause reactions varying from localized discomfort to intense itching, burning, nausea, and cramping. In rare cases, highly sensitive people suffer shock and convulsions. Anyone allergic to other stinging organisms should take special care to avoid being stung as cross-sensitivity is common.

The bell of the sea nettle is milky white frequently with deep red radiating bands. The bells may reach eight inches in diameter and have up to 40 trailing tentacles as great as four to five feet in length. Clustered within the tentacles are four frilly arms coming from an opening under the bell. This opening functions both as a mouth and anus. Internally, the stomach and gonads are the sole organs while rudimentary eyes and balance organs are located on the perimeter of the bell.

The medusa captures food by stunning its prey with toxins emitted from the stinging cells in its tentacles. The stinging cells operate like small poisonous darts. Tightly coiled within their sheath, they spring free when contact is made with prey or a human. Secured in the victim's flesh by barbs, toxins flow through the cell's tube into the prey. The stunned prey is then transported by the tentacles to the mouth and into the central portion of the bell. Partially digested food may be visible through the translucent bell.

Despite our perception of sea nettles as worthless creatures, their sheer numbers force us to recognize them as important links in the Bay's food web. Nettles consume large quantities of comb jellies and zooplankton (small floating aquatic animals). Their consumption of zooplankton in the summer helps to control the numbers of these organisms in surface waters which increases water clarity. In turn, nettles are preyed upon by crabs and some fish. Nettles are 95% water and do not constitute a highly nutritious meal for the animals feeding upon them.

Small sea nettles first appear in the Bay and tributaries in May or June as temperatures warm. Although the nettle can swim by contraction of the bell, its distribution is largely controlled by the whims of the tide and wind. Its distribution is also limited by salinity and nettles are most commonly found in regions with salinity ranges of 7 to 20 parts per thousand. Ocean water is about 35 parts per thousand and freshwater is 0 parts per thousand. Nettles cannot survive in conditions with salinities under about 5 parts per thousand. Thus, the upper reaches of the main Bay and tributaries are generally free of these organisms. There are large amounts of variation in numbers through the summer season, from day to day, and even from hour to hour.

• For real-time reports of sea nettles in the Bay, visit: Mapping Sea Nettles in Chesapeake Bay (NOAA)

As the self-appointed proprietors of the Chesapeake Bay, we tend to take offense at having to share "our Bay" with animals as unpleasant as the sea nettle and its relatives. Yet, it is important to realize that they, like the Bay's many other inhabitants, are critical in maintaining the balance and unity of the system.    Somehow, seeing beauty in the integrity of the whole, makes the task of sharing the Bay with the jellyfish seem just a bit more agreeable. 

To bookmark this page, please use this URL: http://www.chesapeakebay.net/jellyfish.htm

For more information, contact the Chesapeake Bay Program Office:
410 Severn Avenue, Suite 109, Annapolis, MD 21403 / Tel: (800) YOUR-BAY / Fax: (410) 267-5777.

Terms of Use | Privacy Policy | Contact Us
Directions to the Bay Program Office

Last modified: 12/11/03