Florida’s coastal waters host diverse jellyfish species. These fascinating creatures drift through the ocean, often brought closer to shore by currents and winds. Understanding the common types of jellyfish and similar organisms in these waters enhances appreciation for their role in the marine ecosystem.
Common Jellyfish Species
Moon Jellyfish (Aurelia aurita) are frequently observed in Florida. They are recognized by their translucent, plate-sized bell, featuring four pink or purple horseshoe-shaped reproductive organs visible through the top. A fringe of short, fine tentacles lines the bell’s rim. Their mild sting usually results in only minor skin irritation for humans.
The Cannonball Jellyfish (Stomolophus meleagris) is prevalent, particularly abundant along Florida’s southeastern coast during fall and summer. It has a distinctive dome-shaped, creamy white bell with a brown band around its rim, growing up to seven inches in diameter. This species is a capable swimmer and releases a toxic mucus when threatened. Contact can cause mild skin irritation in humans, though it rarely leads to more significant issues.
Atlantic Sea Nettles (Chrysaora quinquecirrha) are common in the Atlantic, Caribbean, and Gulf of Mexico waters off Florida. Their bells measure five to seven inches across, with tentacles extending up to 20 inches. They typically have a clear or cream-colored bell, often marked with brown stripes. Their sting is generally painful but not typically considered life-threatening to humans.
Upside-Down Jellyfish (Cassiopea xamachana) are unique for resting upside down on the seafloor in shallow mangrove swamps and seagrass beds. They display various shades of white, blue, green, and brown, relying on a symbiotic relationship with photosynthetic algae for much of their energy. When disturbed, they release venom-filled mucus into the water, which can cause a sensation often described as “stinging water” or mild skin irritation.
Mistaken Identities
The Portuguese Man O’ War (Physalia physalis) is often mistaken for a jellyfish but is a siphonophore, a colony of specialized organisms. It is identified by its distinctive blue, violet, or pink gas-filled float, which can rise up to six inches above the water, resembling an 18th-century sailing ship. Long, venomous tentacles, averaging 30 feet but capable of extending up to 100 feet, trail beneath the float. Its sting is intensely painful for humans, though fatalities are rare, and tentacles remain potent even after washing ashore.
The By-the-wind Sailor (Velella velella) is another colonial hydroid sometimes confused with jellyfish. This small creature features a flat, oval, deep blue or purple disc with a thin, semi-circular sail that catches the wind, allowing it to drift across the ocean surface. By-the-wind Sailors are typically less than four inches, and their sting is generally mild, posing little threat to humans beyond possible skin or eye irritation. They often wash ashore in large numbers after windy conditions.
Understanding Jellyfish Stings
Jellyfish stings can cause a range of symptoms, from localized pain, itching, and burning to the development of a red or purple rash. More severe reactions might include muscle cramps, blistering, numbness, nausea, or abdominal pain. In some instances, individuals may experience difficulty breathing, chest pain, or profuse sweating, indicating a more serious systemic reaction.
If stung, exit the water immediately to prevent further contact. Rinse the affected area with seawater to help remove any remaining tentacles, avoiding fresh water as it can trigger more stinging cells. Carefully remove any visible tentacle fragments using tweezers or a gloved hand, taking care not to rub or scrub the area, which could release more venom.
For many jellyfish stings, applying vinegar can help inactivate unfired stinging cells on the skin. Immersing the affected area in hot water, around 106-113°F, for 20 to 40 minutes can also provide significant pain relief. Cold compresses or ice packs may be applied to reduce swelling and discomfort, and over-the-counter pain relievers can help manage pain. Medical attention is advised for severe symptoms such as difficulty breathing, chest pain, a large area of stinging, signs of infection, or any indication of an allergic reaction.