The Chesapeake Bay is home to various jellyfish species, which are a natural part of its ecosystem. Understanding the types of jellyfish present helps in appreciating the Bay’s diverse aquatic life.
The Chesapeake Bay Sea Nettle
The Chesapeake Bay sea nettle, Chrysaora chesapeakei, is the most recognized jellyfish in the Bay. Its bell typically has a milky white appearance, though those in saltier, lower Bay regions may show reddish-brown or purplish stripes. The bell can grow up to 8 inches in diameter, with 24 tentacles that may extend several feet. Four long, ruffled oral arms hang from beneath the bell.
The sting of the sea nettle is generally considered moderately painful but is not dangerous for most individuals unless an allergic reaction occurs. These jellyfish are abundant in the brackish waters of the Chesapeake Bay, particularly during summer months. They move with the tides and currents, often concentrating along shorelines.
Other Jellyfish Found in the Bay
Moon jellyfish, Aurelia aurita, are translucent with a flattened, disc-shaped bell that can reach 10 to 12 inches in diameter. A notable feature is the four horseshoe-shaped gonads visible through their bell. Their sting is very mild or often goes unnoticed by humans.
Lion’s Mane jellyfish, Cyanea capillata, are less common in the brackish Bay waters and are usually found closer to the ocean, particularly during winter and early spring. These larger jellyfish can have a reddish-brown color and numerous long tentacles, giving them their characteristic “mane-like” appearance. Their sting is more potent than that of the moon jellyfish, causing moderate pain.
Comb jellies, such as the sea walnut (Mnemiopsis leidyi), are present but are not true jellyfish. They possess transparent, oval-shaped bodies with iridescent comb rows of cilia that refract light. Unlike true jellyfish, comb jellies lack stinging cells and are harmless to humans. They are abundant throughout the Bay and can bioluminesce when disturbed.
Jellyfish Seasons and Patterns
Jellyfish populations in the Chesapeake Bay exhibit seasonal patterns, becoming most abundant from late spring through early fall, with peaks during summer. This increased presence is influenced by environmental factors such as water temperature and salinity. Sea nettles, for instance, thrive in warmer, brackish waters with temperatures between 78 to 86°F and salinities ranging from 10 to 16 parts per thousand.
Jellyfish “blooms” or swarms can occur when conditions are favorable, including adequate nutrient availability and warmer temperatures. These blooms are part of their life cycle, where polyps, which overwinter on the Bay floor, bud off into free-swimming medusae as water warms. Heavy rainfall can temporarily reduce salinity, sometimes causing a decrease in sea nettle visibility.
Interacting Safely with Jellyfish
When enjoying the Chesapeake Bay, exercise caution, especially during peak jellyfish season. Wearing protective clothing like rash guards provides a physical barrier against stings. Avoiding areas where jellyfish are known to congregate, such as windward shorelines, minimizes encounters.
If a jellyfish sting occurs, rinse the affected area with saltwater to remove any remaining tentacles. Use tweezers or a gloved hand to carefully remove visible tentacles without scraping the skin, as this can cause further venom release. For Chesapeake Bay sea nettle stings, a baking soda rinse mixed with seawater is recommended, rather than vinegar, which might trigger more stinging cells. Applying heat to the affected area, such as immersing it in hot water (up to 113°F or 45°C) for 30-90 minutes, can help alleviate pain. Seek medical attention if severe symptoms like difficulty breathing or widespread swelling develop. Dead or stranded jellyfish should not be touched, as their stinging cells can remain active.