Float like a Butterfly, Sting like a Bee: 3 Jellyfish in Barnegat Bay

Those of us who live along the coast of New Jersey are more than familiar with jellyfish. From finding washed up jellies on the sand of our beaches, to spotting the transparent stingers in the bay, jellyfish are an important and well-known part of our native ecosystem. However, in Barnegat Bay, an overabundance of native jellies and a new unwelcome (and potentially dangerous) jellyfish species has caused many to label these organisms as a nuisance. 

In this article, we are going to explore the jellyfish of Barnegat Bay. What exactly are jellyfish? What are our native jellyfish species, and why are there so many of them? And what do we currently know about the clinging jellyfish, an invasive species first spotted in the bay a few years ago?


Jellyfish are marine animals. They are members of the phylum Cnidaria. Cnidarians are aquatic animals that all share a few key traits. Cnidarians have stinging cells called cnidocytes, which they use for protection and to capture prey. Members of phylum Cnidaria also have bodies made up of a jelly-like substance called mesoglea, which is contained between layers of tissue; in jellyfish, this gel layer is very thick, and because mesoglea is made up almost entirely of water, jellyfishes’ bodies are made up of about 99% water. Their body forms also display radial symmetry, meaning that as you spin them, they look the same.

Cnidarians have two main body forms: medusa and polyps. Medusae are bell- or saucer-shaped, with a dome-like top, an opening at the bottom that functions as a mouth, and tentacles surrounding the opening covered in cnidocytes. Cnidarians in the medusa form are most commonly free swimming. Polyps, on the other hand, are sessile, meaning that they are attached to substrates and do not move from one spot. Polyps are shaped like a cylinder, with a mouth at the top surrounded by tentacle-like structures with stinging cells. For an animated video of the medusa and polyp forms, click here


The two main phases of a jellyfish’s life cycle are the polyp and the medusa phase. Here, we can see the entire jellyfish life cycle and how the organism changes form over time. Image credit: Smithsonian Ocean Portal.


Types of organisms that are classified as Cnidarians include corals, anemones, hydrozoa, some parasites, and, of course, jellyfish. Jellyfish in particular are members of subphylum Medusozoa. These animals commonly start their lives as polyps, then grow and develop into adult medusae. They can use their bell-shaped body to move throughout the water, and they use their stinging tentacles for protection and to capture prey. Food sources for jellyfish vary; while many species eat small animals, larvae, and eggs, others are known to eat algae. Jellyfish have been alive for at least 500 million years, making them perhaps the oldest animals to swim in the ocean and also the multi-organ animal group! Jellyfish are found in all of the world’s oceans, and they have been found at a variety of depths, from the surface to deeper waters.


It is important to emphasize the incredible diversity of species commonly known as “jellyfish.” This figure lays out how four species found in the Barnegat Bay— sea nettles, bay nettles, clinging jellyfish, and comb jellies— are all classified by scientists into different groups. Note that comb jellies are Ctenophores, so they are not recognized as jellyfish, even though they may look like jellyfish at first glance. Also note that clinging jellies are hydrozoans and are recognized under subphylum Medusozoa, but not all hydrozoans are jellyfish. Image credit: Brianna Hoegler.

Barnegat Bay: Nettles

Barnegat bay’s endemic jellyfish species is the sea nettle, or Chrysaora quinquecirrha. Sea nettles have an average diameter of 25 cm and tentacles that reach an average length of 50 cm. They have a variable coloration, but are usually white, pale pink, or yellow. They are a stinging species covered in thousands of cnidocytes. While their sting can kill or paralyze their prey, it typically causes a mild, nonlethal rash in humans. 


Image Credit: Corrine Hinton


As of 2017, a distinct species, Chrysaora chesapeakei, another type of sea nettle that is also known as the bay nettle, has been distinguished from C. quinquecirrha. Bay nettles are also found in Barnegat Bay, and they are about half the size of C. quinquecirrha.


As of 2017, bay nettles and sea nettles are recognized as two distinct species. This figure lays out some of the physical differences between the two types of jellyfish. Image credit: NOAA Fisheries


Sea nettles have a diet consisting of mostly zooplankton and ichthyoplankton (fish eggs and larvae). However, studies of sea nettles in Barnegat Bay have found that their diets are extremely varied, as they consume both free-swimming and seafloor-dwelling organisms. Their consumption of species from both the water and the sediment may help cycle nutrients, such as nitrogen, in the bay. 

Sea nettles have lived in the Barnegat Bay for thousands of years, and they can survive in water with more pollution, less oxygen, and lower water quality than many other aquatic organisms. Because of their ability to live in lower-quality water and their reliance on zooplankton as a food source, jellyfish blooms have become more common in productive summer months in Barnegat Bay. This is especially true as eutrophication increases; as more nutrients enter the water, more phytoplankton blooms occur, causing increased zooplankton reproduction and, in turn, increased jellyfish reproduction. The number of sea nettles in Barnegat Bay have also increased due to increased shoreline development, as this increases the number of hard surfaces, such as docks and bulkheads, on which jellyfish larvae and polyps can attach and mature. In Barnegat Bay, consistent increases in sea nettle populations have been recorded since 2006.


Nutrient pollution can lead to a decrease of water quality and an increase of jellyfish population numbers in Barnegat Bay, as laid out in this figure. Image credit: Brianna Hoegler.


Comb Jellies

Another common native species in the Barnegat Bay is Mnemiopsis leidyi. While Mnemiopsis leidyi may look like jellyfish, they are not even Cnidarians; they are members of phylum Ctenophora, commonly known as comb jellies. Although comb jellies have clear gelatinous bodies like sea nettles, they are not jellyfish. Unlike Cnidarians, most Ctenophores do not have stinging cells, so the comb jellies native to Barnegat Bay cannot sting. Comb jellies feed on zooplankton and ichthyoplankton, and they consume such large quantities of plankton that they have the potential to alter planktonic food webs and harm important commercial fish stocks if their population is left unchecked. Ctenophores like comb jellies are important food sources for many species, such as birds and fish. 


Image Credit: Corrine Hinton


Sea nettles feed on comb jellies, which is important to maintaining a healthy bay ecosystem. In a healthy bay system where there is limited eutrophication, an excess of comb jellies could result in the decimation of zooplankton populations. However, sea nettles help regulate this population by consuming comb jellies, a major predator of zooplankton and fish eggs. This is known as a top-down effect: a species closer to the top of the food chain (in this case, sea nettles) protects the balance of the species lower on the food chain (here, comb jellies and zooplankton).

Clinging Jellyfish

While our native jellyfish species can cause little serious harm to humans, a potentially much more dangerous invasive jellyfish has made its way into Barnegat Bay. The clinging jellyfish (Gonionemus verbenas) was first sighted in the Barnegat Bay in 2016. Clinging jellyfish are much smaller than sea nettles, only growing to about one inch in diameter. The body of the clinging jellyfish is mostly transparent, but the bell-shaped medusa has a single red, orange, or yellow cross. 

Clinging jellyfish are small, about the size of a quarter, and they may be difficult to spot because of their mostly clear bodies. However, they have a distinct cross pattern on their bells. Image credit: Mary Carman, WHOI.


Clinging jellyfish are named for their distinctive behavior, in which they “cling” to submerged aquatic vegetation and hide in grass beds during the day. At night, the clinging jellyfish release their hold on the vegetation and feed in the open water on zooplanktonic organisms. 


Image Credit: Corrine Hinton


These jellies may also release their hold on seagrasses if they are disturbed. This presents a danger to those wading through eelgrass beds in Barnegat Bay; if they walk into an area where clinging jellies are resting, the jellyfish are likely to release themselves from the vegetation and sting whoever is nearby. 

Clinging jellyfish are native to the northern Pacific Ocean, and before being common along the northeast coast of the United States, they were also common in the Mediterranean. Clinging jellyfish may have arrived in the east coast as early as the 1890s, when they were found in the Cape Cod area. However, the clinging jellyfish recorded during this time may have been a different variety than those in the Barnegat Bay today, as they had less potent stings. These jellyfish disappeared in the 1930s, most likely due to an eelgrass die-off. However, in the 1990s, clinging jellyfish were again spotted in Cape Cod, this time with much more potent stings that, in some cases, could send humans to the hospital. Now, these jellies are found from Maine to New Jersey.

Clinging jellyfish, like sea nettles, can survive in water conditions that are less than ideal for other species: water that is polluted, eutrophic, warm, and low in oxygen. Continued development of our shorelines, nutrient pollution from pet waste and fertilizers, and climate change are all playing a part in providing ideal habitat for these invasive jellyfish.

It is likely that there are several varieties of clinging jellyfish with different potencies of stings. One study found up to seven different species or subspecies of clinging jellyfish in the Atlantic and Pacific Oceans. The variety now being found on the east coast of the United States shares a genetic variant with the variety of clinging jellies found off of the coast of Vladivostok, Russia— and like the Russian variety, the clinging jellyfish now found here can deliver dangerously toxic and painful stings. WHOI researcher Mary Carman, who worked on the study, suggests that there may be more than one type of clinging jellyfish on the east coast: “The study documents what we suspected, that there are different types of Gonionemus jellies and some of these types co-occur in New England. Some types seem to have a toxic sting to people and some do not.” Future areas of research regarding clinging jellyfish on the east coast of the U.S. include identifying possible pathways through which Gonionemus jellies could have been introduced to the western Atlantic ocean and with how many species or subspecies this occurred. Another area of study is the environmental and evolutionary processes influencing Gonionemus jellies, including the variations that cause some species to have much more potent stings than others.


This is a map of locations sampled in southern NJ where clinging jellyfish have been found. Note that several locations in Barnegat Bay have contained clinging jellyfish this year. For an up-to-date map, click here. Map credit: NJDEP.

An increase in the presence of both sea nettles and clinging jellyfish could result in the decline of recreation and fishing in and near Barnegat Bay. The jellies could deplete stocks of desirable fish species, reduce biodiversity, and create a potentially dangerous environment for any sort of water-based activity. 

Jellyfish Stings

As of 2018, the NJ Department of Environmental Protection (NJDEP) has issued a recreational advisory for clinging jellyfish on the entire Barnegat Bay. This means that anyone in the bay should take care to use caution in areas where clinging jellyfish may be present, notably near shallow areas with vegetation. Using boots or waders can help prevent getting stung. According to the NJDEP, if you are stung, you can do the following: pour white vinegar on the sting site to immobilize the cnidocytes, rinse the area with saltwater, remove any tentacle material with gloves or a towel, use a hot or cold compress to relieve pain, and seek medical attention if symptoms persist or if the pain gets worse instead of subsiding.


Image Credit: Corrine Hinton


Work is being conducted by local scientists and environmental groups to attempt to manage sea nettle populations and to learn more about clinging jellyfish. Individuals may help in these efforts by staying educated about pollution and jellyfish in local waters, reducing nutrient pollution wherever possible (such as reducing fertilizer use), and reporting clinging jellyfish sightings. The NJDEP suggests that if you spot a clinging jellyfish, from a distance take a photo of it and send it to Dr. Paul Bologna at [email protected] or Joseph Bilinski at [email protected] along with location information.

related Posts

May 8, 2023

Barnegat Bay Book Club

Save Barnegat Bay hosts the Barnegat Bay Book Club to celebrate the incredible books written over the years about the...
Read More
Apr 11, 2023


There are upcoming Save Barnegat Bay events. We will be working to engage with you virtually whenever possible! Watch for...
Read More
Jun 14, 2022

Join the Team! – STEM Summer Series: Teacher & Teacher Assistant Positions

STEM Summer Series Job Posting  Join the Borough of Bay Head and Save Barnegat Bay this summer at our STEM...
Read More