aqua.org
The Truth (About) Stings
Summertime beachgoers in the Mid-Atlantic region dread the appearance of stinging jellyfish—particularly when it’s in the form
of a swarm.
Actually not a fish, jellies are 95% water.They have no brain, bones, blood, teeth, or fins. In spite of these limitations, they’re a very
common sight in the Chesapeake Bay, and one of the most common is the Atlantic sea nettle.
Ranging from Cape Cod to the Caribbean, these stinging jellies are often seen in the Bay in high concentrations, especially in the
summer. In fact, if Maryland had a state jelly, the Atlantic sea nettle would be it.
The current buzz is that we’re expecting a larger-than-normal bloom of several species of jellies in the Bay this year, thanks to a warm
winter and spring, and lower-than-average rainfall.This combination—warm water and a saltier Bay—creates the right conditions for sea
nettles to reproduce rapidly.Although this isn’t scary news from an environmental perspective, try telling that to swimmers.
The ocean contains a great variety of jellyfish species, but some, including the Atlantic sea nettle, Lion’s mane jelly, and Leidy’s comb
jelly, can survive in the Bay’s normally lower salinity levels. But it’s the Atlantic sea nettle that dominates all summer long.As the water
temperature drops in the fall, these nettlesome critters die off by the millions.
But don’t be fooled:Atlantic sea nettles are actually in the Bay year round, existing as tiny polyps through the cold winter months,
attaching themselves to oyster shells, pier pilings, and other hard surfaces.While adult sea nettles live for a relatively short time, the
polyps can live for years.
When water temperatures are right and food is abundant, these opportunists expand their populations very rapidly. Reproducing both
sexually and asexually, a single female Atlantic sea nettle can release 45,000 eggs into the Chesapeake in a single day!
Their dreaded sting aside,Atlantic sea nettles are part of a dynamic ecosystem and do provide benefits to other Bay denizens. Juvenile
harvestfish and butterflyfish use the nettles for protection from predators, taking up residence inside the protective barrier of the
stinging tentacles. Much like the clownfish, which hides among the tentacles of sea anemones, these fish species have a mucous coating
that protects them from fatal stings.
Several fish species and all seven species of sea turtles dine opportunistically on jellies. In fact, the endangered leatherback sea turtle, an
occasional visitor to the Bay, feeds almost exclusively on jellies.
The sea nettles also play a role in bay health and the balance of species by eating comb jellies, which feed on fish eggs and oyster larvae.
Some scientists believe that an overabundance of comb jellies may be a factor in the decline of the once-abundant American oyster in
the Chesapeake Bay.The free-swimming oyster larvae hatch at the same time of year that the comb jellies flourish, so oyster numbers are
reduced as comb jellies feast on their eggs and larvae.
The bottom line is Atlantic sea nettles are native to our waters…which means that an occasional sting is inevitable.The concentrations
and locations of nettles vary, however, and new technologies can help you predict the likelihood of getting stung by date and area of the
bay or coast.
The National Oceanic and Atmospheric Administration’s network of buoys in the bay feeds information on water temperature
and salinity into an equation to determine the probability of a sea nettle outbreak. Results are mapped on their website, allowing
Marylanders to check the jelly forecast along with the weather.
To learn more about this topic and get that web address, visit aqua.org/wypr.
I’m John Racanelli from the National Aquarium, for 88.1 WYPR, your NPR news station.
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