Maryland’s coastal waters and the Chesapeake Bay are home to various jellyfish species, prompting many to consider when these marine animals are most prevalent for recreational activities. Understanding the patterns of jellyfish presence helps individuals plan their visits to beaches and waterways. This overview provides insights into the typical “jellyfish season” across Maryland’s diverse aquatic environments.
Understanding Maryland’s Jellyfish Season
Maryland’s “jellyfish season” is not a singular, fixed period but rather spans the warmer months, generally from late spring through early fall. In the Chesapeake Bay, jellyfish are consistently present year-round, though their visibility and abundance increase significantly as water temperatures rise. July and August often mark the peak period for jellyfish in the Bay.
Along the Atlantic coast, including popular destinations like Ocean City, jellyfish populations also become more noticeable during the peak summer months. August and September are considered prime season for jellyfish along the Delmarva coastline.
Key Jellyfish Species and Their Seasonal Presence
Several jellyfish species inhabit Maryland’s waters, each with distinct appearances and seasonal patterns. The Atlantic sea nettle (Chrysaora chesapeakei) is the most commonly encountered species in the Chesapeake Bay. These sea nettles are typically white in the upper Bay, while those in saltier, lower Bay regions may exhibit reddish-brown or purplish stripes. An adult bell can reach up to 8 inches in diameter, with tentacles extending several feet. Atlantic sea nettles are abundant in the Chesapeake Bay from May through October, thriving primarily from July to September.
Another common species is the moon jellyfish (Aurelia aurita), which appears in the lower Chesapeake Bay during summer. Moon jellyfish are characterized by their translucent, saucer-shaped bell, which can grow up to 12 inches in diameter. Their short, frilly tentacles deliver a very mild sting that typically does not harm humans. They are found in both the Bay and along the Atlantic coast.
While less common, cannonball jellyfish (Stomolophus meleagris) can also be found in Maryland’s coastal waters. These jellyfish have a distinct dome-shaped bell that can reach 10 inches in diameter, often with a brown-pigmented rim, resembling a cannonball. Cannonball jellyfish have short, protruding oral arms and lack long tentacles.
Environmental Factors Shaping Jellyfish Season
The timing and abundance of jellyfish in Maryland’s waters are closely tied to specific environmental conditions. Water temperature is a primary factor, as many jellyfish species, including sea nettles, thrive in warmer waters. Sea nettles, for instance, prefer water temperatures between 78 and 86 degrees Fahrenheit, which typically occur during the summer months. Warmer springs can lead to earlier appearances and potentially larger jellyfish populations.
Salinity levels also significantly influence jellyfish distribution, especially in the brackish Chesapeake Bay. Sea nettles are uniquely adapted to lower salinity waters, preferring ranges between 10 and 16 parts per thousand (ppt). Dry years with less freshwater runoff into the Bay can lead to higher salinity further upstream, allowing sea nettles to extend their range into areas they might not typically inhabit. Conversely, heavy rainfall can reduce salinity, limiting their distribution.
Nutrient availability plays a role in supporting the food sources for jellyfish, influencing their growth and reproduction. Increased nutrient pollution can lead to more algae, which benefits jellyfish by providing more food. Ocean currents and tides also affect where jellyfish are transported, as these creatures depend on water movement for their distribution.