Jellyfish are over 560 million years old. They have no brains and no spines, yet these gelatinous animals are among the worlds’ most successful organisms. While other creatures evolved to develop tails and feet, jellyfish continued to thrive staying just the same. But lately scientists are concerned the animals are thriving too well — overrunning beaches, forcing nuclear power plants to shut down and disrupting the ecosystem. And experts say it is human-caused changes to the environment that’s behind the rise in jellyfish. For our June Environmental Outlook, Diane and her guests discuss jellyfish and the health of the ocean.


  • Lisa-ann Gershwin Author of "Stung! On Jellyfish Blooms and the Future of the Ocean" and director of the Australian Stinger Advisory Services.
  • Bill Dennison Vice president for science applications and professor at the University of Maryland Center for Environmental Sciences.
  • Jack Cover General curator at National Aquarium.

Jellyfish At The National Aquarium

All images copyright National Aquarium ©.

Little-Known Facts About Jellyfish

Courtesy of the National Aquarium

Leidy’s Comb Jellyfish

  • The comb jelly looks different from other jellies because it’s not made up of a bell and tentacles. Instead, it is a translucent walnut-shaped body with wart-like bumps. For this reason, it’s sometimes called a sea walnut.

  • Comb jellies are translucent but refract light, appearing to have rainbow colors running down their bodies on the track of internal moving cilia. They can also make their own light (bioluminescence), flashing when disturbed.

    Spotted Lagoon Jellyfish

  • These spotted jellies have rounded bells and strange clumps of oral arms with club-like appendages that hang down below.

  • Instead of a single mouth, they have many small mouth openings on their oral arms.

    Purple-Striped Jellyfish

  • This jelly has a white bowl-shaped bell with 16 purple stripes, and very long tentacles.

  • Young crabs are often found hitching a ride in this jelly’s bell. This is a symbiotic relationship—by eating parasitic amphipods that damage the jelly, the crabs get a free meal, and the jelly gets a free cleaning.

    Pacific Sea Nettle Jellyfish

  • The Pacific sea nettle’s bell is yellow to reddish-brown, and the long, ruffled tentacles can be yellow to dark maroon.

    Northern Sea Nettle Jellyfish

  • This jelly’s bell can be white to dark purple/red, with dark lines radiating from the top of the bell. The species derives its name from the Greek words melas and aster, which translates to “black star” in reference to the pattern on its bell.

    Moon Jellyfish

  • Translucent white, saucer-shaped bell, with a blue-gray transparent disk at its center through which the horseshoe-shaped gonads are visible. Short, delicate, fringe-like tentacles hang from the bell margins.

  • When deprived of food, they can shrink to 1/10th of their original size to save energy. They redevelop to normal size when food is available.

    Blue Blubber Jellyfish

  • This venomous jelly can be safely eaten once it’s been correctly dried and processed. Dried jellies are popular in many Asian countries, especially Japan, where they’re considered a culinary delicacy. The texture is reportedly crispy, yet elastic—hence the name “rubber band salad” for a dish sold in China. The Chinese believe eating jellies will reduce high blood pressure.


  • 11:06:56

    MS. DIANE REHMThanks for joining us. I'm Diane Rehm. For many people the word jellyfish means just one thing, fear of being stung. But for scientists who study them, jellyfish are fascinating creatures, beautiful and strange and now according to some experts more numerous than ever.

  • 11:07:16

    MS. DIANE REHMFor this month's Environmental Outlook understanding jellyfish and their connection to a changing environment, here with me is Bill Dennison of the University of Maryland, Center for Environmental Sciences, Jack Cover from the National Aquarium and joining us from Omaha, Neb. Lisa-ann Gershwin. She's author of a new book titled "Stung! On Jellyfish Blooms and the Future of the Ocean."

  • 11:07:48

    MS. DIANE REHMThroughout the hour, I'll look forward to hearing your comments. Join us on 800-433-8850. Send us your emails to Follow us on Facebook or send us a tweet and good morning to all of you.

  • 11:08:09

    MS. LISA-ANN GERSHWINGood morning.

  • 11:08:09

    MR. BILL DENNISONGood morning.

  • 11:08:09

    MR. JACK COVERGood morning.

  • 11:08:10

    REHMGood to have you with us. Lisa I'm going to start with you after I tell folks that if you go to our website you'll see photographs of different types, different species of jellyfish and they are gorgeous. You'll also see some little-known facts about jellyfish up there on the website and let's start with the basics Lisa because these jellyfish are not fish. What are they?

  • 11:08:51

    GERSHWINWell, they're actually invertebrates so they're in a phylum that contains the corals and the sea anemones and all of those fabulous weird creatures, very, very low on the evolutionary tree. And all of these creatures have stinging cells and that's why we think of jellyfish as things that sting but like you so rightly pointed out earlier that jellyfish are really causing a lot more problems than just stinging.

  • 11:09:19


  • 11:09:20

    GERSHWINAnd this is something that we didn't realize for many, many, I mean well for all of history really and it's only been in the last, you know, few years that we've come to realize that jellyfish are capable of absolutely devastating ecosystems. They're not only capable but they actually are.

  • 11:09:37

    REHMIt's interesting because I grew up thinking that cockroaches were going to be the last creatures...

  • 11:09:47


  • 11:09:47

    REHM...left on earth but you seem to imply that these jellyfish are reproducing in such quantities that indeed they may replace the cockroaches. First I want to turn to you Jack Cover. You call jellyfish living lava lamps. What do you mean?

  • 11:10:11

    COVERWell for one thing aquariums have display jellies and it took us sort of a long way first of all to figure out how we could keep jellyfish in an aquarium setting. You have to re-create their environment. But we first weren't sure how visitors would sort of receive looking at jellyfish and you could see from those images they really are beautiful animals.

  • 11:10:35

    REHMYou called it an animal?

  • 11:10:37

    COVERYeah, they're animals.

  • 11:10:38

    REHMYou wouldn't think of it as an animal.

  • 11:10:41

    COVERThey're definitely, yeah they're definitely animals and they're, again they've been around a long time. They've been around for over 500 million years. They don't have a brain. They don't have any bones. They don't have blood. They're very simple animals so.

  • 11:10:56

    REHMSo what gives them their color and their shape?

  • 11:10:59

    COVERWell, basically again with the types, different types of jellies, there are different classes and Scyphozoas are the kind of classic Medusozoa jellyfish, the one that has the umbrella that pulses with the tentacles. So there are many beautiful ones and then there's a whole different phylum, the Ctenophores which we loosely classify as jellies too that are not stinging.

  • 11:11:25

    COVERThey can produce colors and I think we have an image of one of those. They can actually refract light but we in, what we find is in our displays that we were first wondering how people would receive them because most people really remember jellyfish as something that stung them when they were...

  • 11:11:38


  • 11:11:38

    COVER...on their vacation.

  • 11:11:40


  • 11:11:40

    COVEROr that gobby thing on the beach but when we found we could display them we found that visitors were fascinated by their movements, by their colors.

  • 11:11:51


  • 11:11:51

    COVERAnd it's really relaxing and so it really is like you go into our jelly room, our display at the National Aquarium. It's very relaxing.

  • 11:11:56

    REHMAnd Bill, they're not only relaxing you call them very cool.

  • 11:12:04

    DENNISONI think they're amazing animals. One term that we use is they're just organized water. There's very little actual organic material in the jelly. So if you dry a jelly down and take out all the water you end up with, in fact what's left is even. Most of that isn't even organic, it's salts.

  • 11:12:25

    DENNISONSo jelly is a very loosely organic material that has captured water and does amazing things with it. They can move, even some of them can swim quite strongly against currents. So they're amazing what they can do with so little.

  • 11:12:47

    REHMAnd Lisa what do they actually eat?

  • 11:12:50

    GERSHWINWell, most jellyfish will eat just about anything they can get their lips around but what concerns us the most is that they have a strong propensity to eat eggs and larvae of other species.

  • 11:13:08

    REHMI see.

  • 11:13:08

    GERSHWINAnd they also eat the plankton that the larvae would eat. So this double whammy of predation and competition can actually flatten populations of fish and crustaceans and mollusks and all of these things that make up a healthy ecosystem. They not only flatten it but they can keep these populations from coming back through this double whammy.

  • 11:13:31

    REHMAnd you write that the way jellyfish reproduce is "straight out of science fiction". Talk about that.

  • 11:13:42

    GERSHWINAh, it's true. They can clone in 13 different ways. They have a weird, weird lifecycle that's nothing like anything we know where when the jellyfish have babies they don't grow up to look like jellyfish. They grow up to look like little, tiny sea anemones or little coral polyps.

  • 11:14:02

    GERSHWINAnd they have this weird sort of alternation of generations and this allows them to be the weedy, weedy creatures that they are because they can hide in their little, tiny vases that are stuck to rocks and shells and things. And then when the conditions are right they bloom in fantastic numbers and we see unbelievable blooms of jellyfish sometimes that cover thousands of miles, you know in those sorts of numbers. Each one of them is looking to eat whatever it can.

  • 11:14:37

    REHMLisa-ann Gershwin, she's the author of a new book, its title "Stung! On Jellyfish Blooms and the Future of the Ocean." Talk about how you are connecting those two elements Lisa. As you talk about the future of the ocean, how are jellyfish affecting it?

  • 11:15:07

    GERSHWINWell, we're seeing many places around the world that are heavily disturbed by human activity through either overfishing or pollution or warming water or a variety of different impacts or sometimes a combination of impacts. And these damaged ecosystems are actually flipping to being dominated by jellyfish instead of fish.

  • 11:15:28

    GERSHWINAnd it's a very frightening thing when you think that something so small and insignificant can have such an incredible power to transform the oceans in ways that aren't very good for us. And we're actually seeing this happening in many places around the world already.

  • 11:15:47

    REHMBill Dennison, would you agree?

  • 11:15:49

    DENNISONWell, I think Lisa's got a point that an overabundance of jellyfish is a symptom of a system that's out of whack, but some of my scientific colleagues have recently published a series of papers earlier this year that talk about -- they went and looked for the data that supports that assertion that jellyfish are flipping and taking over the ocean.

  • 11:16:15

    DENNISONAnd what they're finding, in fact there's a 20-year cycle of jellyfish blooms and declines. And so the reports are all focused on the increases...

  • 11:16:23

    REHMI see.

  • 11:16:23

    DENNISON...and so you tend to focus on that. And then secondly that looking at it globally there are places and Lisa brings it out really well in the book of introduced species like into the Black Sea where jellyfish have taken over. But overall they're not seeing a major trend, maybe since 1970 a slight increase but nothing catastrophic.

  • 11:16:49

    REHMNow, would this be in all the oceans, Lisa, or are you just talking about one ocean?

  • 11:16:59

    GERSHWINNo, it's in all the oceans, but it's not every species and it's not every species everywhere. So the papers that my colleague has just referred to looked at a larger scale where they looked at every species everywhere and found that there was so much noise that a pattern couldn't be discerned.

  • 11:17:22

    GERSHWINBut when you look at certain disturbed areas and you look at certain types of species in these certain disturbed areas, we are finding dramatic increases.

  • 11:17:29

    REHMExplain what you mean by disturbed?

  • 11:17:33

    GERSHWINWell, overfishing seems to be a really common thread, although it's not the only thread, but that is a common thing that's happening in many of these disturbed places that are being taken over by jellyfish. Also, what we call eutrophication, which is kind of a fancy word for too much fertilizer.

  • 11:17:55

    GERSHWINSo when coastal areas have too much farm fertilizer running down in the rivers or too much sewage affluent from cities, we see these chemistry changes in the water that jellyfish can do really well in these areas, but many other species can't because of a change in the oxygen.

  • 11:18:20

    GERSHWINThere's not enough oxygen for most species to be able to survive and you know, there's warming waters as well. Jellyfish can do really well, but other species that need to get oxygen from the water, of course, warming -- sorry, warm water holds less oxygen than cold water so the jellyfish can do better.

  • 11:18:38

    REHMLisa-ann Gershwin, her new book is titled "Stung! On Jellyfish Blooms and the Future of the Ocean," do join us, short break and right back.

  • 11:20:05

    REHMAnd for this month's environmental program we are talking about jellyfish. And with me here in the studio, Bill Dennison. He's vice-president for science applications, professor at the University of Maryland Center for Environmental Sciences. Also Jack Cover. He's general curator at the National Aquarium. Joining us from Omaha, Neb. Lee-Ann Gershwin. She is the author of a new book. It's titled "Stung!: On Jellyfish Blooms and the Future of the Ocean. She's the director of the Australian Stinger Advisory Services.

  • 11:21:00

    REHMHere's an email saying, "Does anything eat jellyfish? Jack Dover.

  • 11:21:07

    COVERWell, there's actually a number of animals that do eat jellyfish. All seven species of sea turtles will opportunistically feed on jellyfish. In fact, the largest sea turtle, one of the largest reptiles in the world, the leatherback sea turtle is a jelly-vor. And here, Bill was talking about the percentage. Jellies are 95 percent water, but this particular sea turtle will actually travel -- lay its eggs in the tropics on a beach in Suriname, travel thousands of miles up into Nova Scotia into very cold water. Because that's where we have some incredibly large jellyfish in big booms.

  • 11:21:42

    COVERSo it -- actually you just will mine through the jellyfish. There's also a lot of fish that eat jellyfish. And relationships here in the Chesapeake Bay, we see at the end of the summer, we see some fish that their larvae, their young fish will hide in the jellyfish stingers. They're protected. They actually have a mucous that protects them.

  • 11:22:03

    REHMMy goodness.

  • 11:22:03

    COVERAnd this is the butterfish and harvest fish, and kind of a dirty trick. Eventually when they grow they actually then start eating the jellyfish. So all's friar in nature when it comes to survival with their -- a lot of things depend on jellyfish. They are part of the ecosystem and we have to have them.

  • 11:22:19

    REHMAnd, Bill Dennison, tell me about these man-o'-war jellyfish.

  • 11:22:25

    DENNISONThe Portuguese man-o'-war, which is...

  • 11:22:29


  • 11:22:29

    DENNISON...huge, long, long tentacles. And my personal experience was not -- my first encounter as not a pleasant one. I ended up getting a whole swath of stingers across my neck. I could feel my heart begin to race...

  • 11:22:43

    REHMWow, wow.

  • 11:22:44

    DENNISON...because it's got this toxin in it. But they're very -- they're commensal (sp?) and they have lots of different organisms living together, including a lot of fish that live down in the tentacles. And so they're beautiful purple and pink and translucent. And these things blow across the ocean. Some of these are -- you can find these out in the middle of the ocean as well as coastal.

  • 11:23:12

    REHMAnd you can find them -- I was once in Bermuda and could see them coming fairly close to the shore. What about those larger types, Lisa. Are they also reproducing in quantities that give you concern?

  • 11:23:36

    GERSHWINWe're not seeing the man o' war in any sort of problematical blooms that I'm aware of. I mean, we certainly do get vast armadas of them blowing ashore seasonally. But they don't seem to be responding to these different stressors in the same way that some other species are, which is a good thing because they are very stingy. And of course they can even kill people. But they don't seem to be doing the damage to the eco system that we're seeing with others.

  • 11:24:04

    REHMAnd what kind of damage do you really believe could be happening for the long term as opposed to as Bill Dennison pointed out earlier, part of a natural 20-year cycle?

  • 11:24:23

    GERSHWINWell, jellyfish do bloom as a natural part of their own lifecycle but it's more a matter of when the conditions are right. They're simply exploiting the conditions that we're giving them. You know, the warming water, the lack of predators and competitors, the changes in oxygen, the changes in water chemistry. And as it becomes harder and harder for fish to survive these conditions, the jellyfish are taking up that slack, or in some cases, they're just the last man standing.

  • 11:24:56

    GERSHWINLike I said earlier, it's not every jellyfish species in everyplace but there are some of these locations around the world where some types of jellyfish are responding in ways that are not good for us at all.

  • 11:25:08

    REHMAnd you write about Fukushima. Talk about that and nuclear waste.

  • 11:25:16

    GERSHWINYes. We've certainly dumped an awful lot of nuclear waste through the years. And I don't know of any direct correlation between nuclear waste and jellyfish. But again, as it gets harder for other species to survive, jellyfish are often simply not affected by these same problems.

  • 11:25:36


  • 11:25:37

    GERSHWINAnd they're just the last man standing.

  • 11:25:39

    REHMAnd Jack Cover, as you direct the aquarium and have this jellyfish exhibit, what kinds of research are you doing there?

  • 11:25:53

    COVERWell, we're looking again -- and the biggest thing we're doing is really trying to bring this topic to our visitors. But we're -- you know, again when we're stalking this exhibit, we're out on the bay every year sort of looking at the jellyfish populations. And they do go up and down. And as Lisa said, jellyfish are opportunistic. If there's food there for them and we have fortunate challenge with the Chesapeake Bay as well as the Mississippi River where there's a lot of nutrients going in. We have dead zones in the bay and the Atlantic sea nettle seems to do quite well.

  • 11:26:29

    COVERBut to just tell you the potential, you know, again for their populations and how you -- one day you're on the bay, you see three jellyfish. The next day you see thousands of jellyfish. The Atlantic sea nettle, a female can lay 45,000 eggs every day. So...

  • 11:26:45


  • 11:26:45

    COVER...that's why it's this geometric progression. But what we -- at the aquarium in our exhibit is called jellies invasions oceans out of balance, we really present, you know, all these things. And we also try to let people know they're connected to the bay, to the ocean. One would never think that the amount of fertilizer you put on your lawn actually has in effect jellyfish. So if you over fertilize your lawn, you're a friend of jellyfish. You're basically putting more nutrients in. And all these things are connected.

  • 11:27:20

    COVERSo that's really a mission in the aquarium is really to try to show that we are a part of this big, big system.

  • 11:27:26

    REHMBut explain how a person living in the city fertilizing his or her lawn helps to feed the jellyfish.

  • 11:27:37

    COVERWell, what happens is we're -- again, we're -- if you're in the Chesapeake Bay watershed, picture that as a big bowl. Every time it rains everything on the sides of that bowl wash into the bay, which eventually empties into the ocean. So if you're -- Americans are sort of obsessed with this lawn thing, you know, way too much. But we basically over fertilize our lawn and we put more fertilizer than the lawn can use. So every rain event, that all washes into a local stream which washes into a river which washes into the bay.

  • 11:28:07

    COVERSo what we're doing, we're feeding algae blooms. So we are over fertilizing the bay. Suddenly you'll have this bloom of algae that's consuming all this nitrogen that we're putting into the bay. That will eventually eat all the nitrogen and it will be a massive die-off of the algae, which then sinks to the bottom. And then we have a bacterial bloom. The bacterial bloom sucks all the oxygen out of the water, so we have what we call a dead zone.

  • 11:28:35

    COVERFish that are in -- crabs that are in that dead zone, they're dead. Jellies, again, can really survive really low oxygen levels. So they're basically doing fine and the fish that have been eliminated were competitors to the jellyfish. There's more food for them.

  • 11:28:51

    REHMAnd Bill Dennison, right now in the Chesapeake, for example, what are we seeing as to the crab population to jellyfish population?

  • 11:29:06

    DENNISONWell, Diane, the Chesapeake Bay crab story is actually a pretty good story because we've had some aggressive moves by Virginia and Maryland to reduce the catch of pregnant females. And so now our crab population seems to be stabilized and we are hoping to start to see an increase. We had a couple good years that wasn't so good but we think we have management under control.

  • 11:29:34

    DENNISONThe jellies, we had a guy, one of our faculty for 25 years walked up and down the dock every day at noon and counted...

  • 11:29:42


  • 11:29:43

    DENNISON...counting the jellies and saw that they went up and then they went down depending on the rain and weather. But no long term trend. That's for the sea nettles. And one of the things that we're starting to look at for the bay is the impact of all the nutrient that we put in from lawn fertilizer...

  • 11:30:04


  • 11:30:05

    DENNISON...but agricultural and sewage. And we got some good news recently. So we're actually reducing the amount of fallout from the atmosphere. There's less nitrogen coming down. The Clean Air Act is working so we're actually reducing the nitrate in the streams and the forested parts of the watershed. We're looking at our sewage upgrades that we've instituted throughout the bay and they're working. So we're getting some recovery of the smirch grasses. And that provides us positive synergy.

  • 11:30:36

    REHMOkay. I want to go back and ask you about that experience of being stung by a man o' war and where you were and how it affected you both short and long term.

  • 11:30:50

    DENNISONOh yeah, the man o' war, and I should point out, the reason they are called the Portuguese man o' war is because they have a sail, a balloon that they inflate with gas and that sticks above the surface and catches the wind. And so it moves its sails.

  • 11:31:04

    REHMYes, I've seen it.

  • 11:31:07

    DENNISONYep. And I was in St. Croix and I was training to be an aquanaut on one of the underwater habitats, so I was swimming. Part of my training was to swim and I'd swim offshore pretty far, like a mile. And then turn around at this buoy and swim back.

  • 11:31:23

    REHMAnd had you been told that man o' war were present?

  • 11:31:27

    DENNISONNo. And, you know, you don't always have good warning for it. And I did see -- I did look -- once I got stung I looked up and saw the sail but the sail was 30' away.

  • 11:31:38

    REHMI see.

  • 11:31:39

    DENNISONThose tentacles are really long. They string out through the water.

  • 11:31:44


  • 11:31:44

    DENNISONSo, anyway I was pretty far away from shore so what I was worried about is my heart rate started racing. And I did have a stinger shirt on but not a -- it didn't protect my neck. You know, Australia, when you go in the water you tend to wear a full-body suit and you don't expose much skin.

  • 11:32:04

    REHMYou don't fool around.

  • 11:32:05

    DENNISONWell, it turns out the little stingers, the pneumatosis (sp?) which are these spring-loaded little traps that spring a little dart with the toxin into your skin, they're relatively short. So even pantyhose or a Lycra suit is thick enough to keep the stinger from actually penetrating your skin. So as long as you have something on your skin surface, you're protected. But it's hard often to cover your entire body, particularly your face and neck if you've got a mask and snorkel on. So that's where I got, across my neck and that was probably as far away as I'd want to be and feel that badly.

  • 11:32:46

    REHMAnd you managed to swim back in.

  • 11:32:50


  • 11:32:50

    REHMHow long did that man o' war hold on?

  • 11:32:55

    DENNISONOh, I think it probably washed off right away but those pneumatosis are -- you know, you could actually count the sting across your neck.

  • 11:33:02

    REHMI would not wish to do that, thank you. And you're listening to "The Diane Rehm Show." We've got some questions on our lines so let's open the phones. First to Rick in Fayetteville, N.C. Good morning to you.

  • 11:33:22

    RICKOh, good morning, Diane.

  • 11:33:23


  • 11:33:26

    RICKYeah, my question for your guests, kind of taking the analogy of a forest, which is a complex ecosystem like the ocean. And when you, you know, clear cut a forest, the first thing you have grow back are grass and shrub. So I was wondering if in the process of, you know, over fishing and everything else that we're doing to destroy the ocean, if we're not creating basically a clear cut area and jellyfish are just the first thing that start to come back because they're so resilient?

  • 11:33:53


  • 11:33:55

    GERSHWINLook, that's a really good question and yeah, that is the first thing that is kind of coming back. But it doesn't seem to be part of a succession because of this double whammy of predation and competition. We're not seeing the rest of the succession take place. Many of these disturbed ecosystems that have flipped to jellyfish domination have been going this way for decades and there doesn't seem to be any changeover to what's next.

  • 11:34:27

    GERSHWINMaybe it's just too short a period of time. Maybe something will take over but of course the stimuli that have caused the disturbance in the first place are still happening. We're still fishing. We're still discharging nutrients. We're still warming the waters, etcetera, etcetera.

  • 11:34:42

    REHMAnd why is it, Lisa, that as you argue in your book, more than any of the factor temperature both stimulates and controls jellyfish populations?

  • 11:34:59

    GERSHWINWell temperature is very complex. Warmer water stimulates just about everything to grow faster, breed more, etcetera, etcetera. You know, our own metabolisms speed up when it's warmer. So that's a common thing that we see. In the case of jellyfish, they're not affected by it very much. If it gets too warm, yeah, okay, they're affected. But by then everything else is seriously affected. But because colder water holds more oxygen and warmer water holds less oxygen, things that need to breath more struggle way before jellyfish are in any distress at all.

  • 11:35:40

    REHMI see. All right. Let's take a caller in Jacksonville, Fla. Hi there, Robert.

  • 11:35:49

    REHMGood morning, Diane.

  • 11:35:51

    REHMGood morning.

  • 11:35:51

    ROBERTI have always been interested in turtles and I've noticed that over the years the decline of turtles goes along with the increase of jellyfish. The turtles seem to have jellyfish as one of their main diets. And I'm wondering what your guests think about that. And also the box jelly, which is I believe one of the smallest and one of the most dangerous and has one of the strongest pneumatosis that can kill you within a very few minutes.

  • 11:36:27

    ROBERTAnd I walked one year for looking for jelly -- excuse me, for turtles in the beach area in my area. I found one next that had 180 eggs in it. But the point being that when those eggs were hatched very few of them survived -- the turtles that is. That's the next I was looking for. But I'm wondering what they think about the decrease of turtles and the increase of jellyfish.

  • 11:36:56

    REHMAll right. And Bill Dennison.

  • 11:36:59

    DENNISONWell, those are a couple really good points and I think the decline of sea turtles worldwide is really a big concern. And it usually has much more to do with the fishing pressure, a lot of nets that are not intended to catch turtles, catch them. And they're reptiles which need to breath air, so if they don't get to the surface they suffocate and they drown. So there's this movement to put turtle exclusion devices in the nets to allow them to escape. And then secondly, people eat the eggs particularly in developing countries.

  • 11:37:32

    REHMBill Dennison. He's professor at the University of Maryland Center for Environmental Sciences. Short break here. More of your calls when we come back.

  • 11:40:02

    REHMAnd for this month's Environmental Outlook, we're talking about jellyfish. And of course, as a young girl living here in the Washington area, going down to North and Chesapeake beaches I would encounter them a great deal in those areas. But we just had John send us a photograph. He says he Googled images for jellyfish blooms and came up with a picture that makes certain jellyfish look as big as a human. Are they real jellyfish? And I'm holding this photograph up for our two guests here in the studio, Bill Dennison and Jack Cover.

  • 11:40:58

    REHMSee, Lisa, you'll just have to wait and see it on our website, at How much do you figure, Jack Cover, this jellyfish weighs?

  • 11:41:13

    COVERThat particular species is a Nomura jelly, and they're about the weight of a grizzly bear. They can be 450 to 500 pounds.

  • 11:41:20


  • 11:41:21

    COVERAnd that's actually not even the largest species. There's a species called the lion's mane jelly that you would find up in Nova Scotia that's even bigger than that. The lion's mane would have a bell about 10 feet across. It's just like a big satellite dish, with tentacles that trail about 100 feet behind it. So that's like school bus lengths of tentacles.

  • 11:41:41

    REHMSo what happens when a whale, for example, or a shark confronts a jellyfish that is that big, Bill Dennison?

  • 11:41:54

    DENNISONWell, I think they avoid them.

  • 11:41:58

    REHMThey avoid them.

  • 11:41:59

    DENNISONThey definitely do. It turns out, you know, the turtles go and find them and eat them.

  • 11:42:08

    REHMEven the big ones?

  • 11:42:09

    DENNISONNot the huge ones.

  • 11:42:11

    REHMNot the huge ones.

  • 11:42:12

    DENNISONBut one of the reasons why helium balloons and plastic bags are a problem in terms of trash is they make their way into the sea. You know, the balloons float away and land in the sea or the plastic bags, the shopping bags…

  • 11:42:30


  • 11:42:30

    DENNISON…float down the drain and into the sea.

  • 11:42:32


  • 11:42:32

    DENNISONAnd the turtles mistake those for jellies.

  • 11:42:37

    REHMOh, I see.

  • 11:42:37

    DENNISONAnd they can't congest them and some of the turtles they've found stranded, their stomachs are just packed full of plastic…

  • 11:42:44

    REHMTrash bags.

  • 11:42:45

    DENNISONYeah, so that's a real -- and it stops up their gut.

  • 11:42:47

    REHMYeah, have you, Lisa, ever seen one of these gigantic jellyfish?

  • 11:42:55

    GERSHWINOnly in photos and they are incredible. You know, they really are that big and they're toxic. They sting as well. But it's amazing because about a half a billion or 500 million of these things are drifting into the Sea of Japan fishing grounds every day. So, you know, from China, where they're just breeding and breeding and breeding. So you can imagine the havoc that those sorts of numbers are causing in Japan.

  • 11:43:25

    REHMI gather they're also getting caught up in these fishing nets. Bill Dennison, you said you had seen one catch when what happened?

  • 11:43:37

    DENNISONWell, we had a trawl that we took through to catch fish and unfortunately we encountered a big swarm of jellyfish, brought them up and then as we lifted that net up with a hydraulic wench, it was out of the water, the whole stern of the boat went under and we started getting water onto the deck. So we had to put the net back in and go in and pull the cod and open and release the net because we literally couldn't bring it onto the boat.

  • 11:44:10

    REHMLisa, how long would a jellyfish, say in the Sea of Japan, live to reach this enormous size?

  • 11:44:22

    GERSHWINYeah, that's a really good question. We don't know how long the Normura's jellyfish live, but we think that they are born, grow and die within a season. So these things are starting out as just tiny, tiny little things, about as wide as a dime is tall, if it's laying flat on a desk. And, tiny, tiny, little things, you know, the width of a dime. And they grow up into these enormous sizes, the size of refrigerators.

  • 11:44:52

    REHMIn one season?

  • 11:44:54

    GERSHWINYeah, in a matter of months.

  • 11:44:56


  • 11:44:56

    GERSHWINAnd, you know, because they're eating so much plankton that's in the water.

  • 11:45:01

    REHMI see.

  • 11:45:02

    GERSHWINBut that means that other things aren't able to eat that plankton.

  • 11:45:05


  • 11:45:05

    GERSHWINSo, you know, that balance has been shifted so…

  • 11:45:09

    REHMAll right.

  • 11:45:09

    GERSHWIN…completely over to jellyfish.

  • 11:45:11

    REHMLet's go to Westchester, N. Y. Good morning, Bob.

  • 11:45:16


  • 11:45:17


  • 11:45:19

    BOBI love the show and…

  • 11:45:19


  • 11:45:20

    BOB…I was a bayman on Long Island for about 20 years and I'm still representative of a baymen's association on Long Island. I had a question for the guests.

  • 11:45:31

    REHMGo right ahead.

  • 11:45:34

    BOBSo this time of the year we see -- we refer a common name as Comb jellies, but I'm not positive of the genus and species. They bloom and their bloom seems to coincide with the time when clams and oysters spawn. So the free swimming larvae from the clams and oysters, which is part of the plankton for a week or two weeks, is, I think, one of the primary foods of these jellies. And I wanted to know what the guests thought about the effect on shellfish larvae in the water column.

  • 11:46:16


  • 11:46:17

    DENNISONYeah, Bob, that's a good question. I actually was at Stony Brook for a few years. So I know the waters around Long Island. And that Comb jelly that you were seeing is most likely Mnemiopsis leidyi. It’s a beautiful little thing, and they are voracious. They eat fish larvae and plankton. In Chesapeake Bay -- we've got them down here, too. And one of the things that we've learned is that the sea nettle, the big, stinging nettle, actually the oyster larvae can pass through them intact. So they might ingest them, but the larvae escape, where they don't escape the Comb jelly.

  • 11:47:01

    DENNISONThe Comb jelly, which is a Ctenophora, not a true jellyfish, but they are voracious and they do eat fish larvae.

  • 11:47:07

    REHMAll right. And, Jack Cover, to what extent are you concerned, as Lisa is, that this may not be simply a 20-year cycle, but that, in fact, the jellyfish are proliferating and cleaning out the ocean for their own consumption, leaving waters affected rather substantially?

  • 11:47:42

    COVERWell, some things we know for sure. We know that human activity, we are, number one, transporting jellyfish all over the world. For example, ships going from the Mediterranean over to this part of the world, when they take off all of their cargo they oftentimes take on ballast water. So the little leidyis Comb jelly that Bill was just talking about, was transported to the Black Sea in the early '80s. It went into the Caspian Sea. It went into all these different areas. So we definitely know that they're an invasive species. We're seeing Australian jellies show up around the U.S.

  • 11:48:22

    COVERSo we definitely have an invasive species issue. I think that, you know, it's an altered world. I think the things the humans are doing, unfortunately, are affecting the bio-diversity. So I would agree that, you know, as we do unnatural things, we catch large numbers of fish and we get more proficient at catching those fish. So what we really have to do is pay attention to what the scientists are seeing and react to it. But there's long-term studies, and like I say, we -- I think the jury is still out, but I would say that definitely we are living in a different world and the jellies have been around without a brain for over 500 million years.

  • 11:49:07

    COVERHumans haven't been around too long. We sort of came at one minute before midnight to the party, and we're sort of wrecking the house. So we really need to look at many of our activities and make sure that we're not knocking the ocean out of balance, acidifying it.

  • 11:49:22

    REHMAll right. To Fredericksburg, Va. Hi, Bobbie. Thanks for waiting.

  • 11:49:27

    BOBBIEWell, I love your show, like everybody else does.

  • 11:49:29

    REHMThank you.

  • 11:49:32

    BOBBIEListening to that last part about how big they can grow, stuck terror in my heart because my introduction to Boston, as a little Southern girl from Virginia moving up there, where my husband was from, we went into the waters. And I think it was Wollaston or else Nantasket Beach and I, you know, you don't have the ocean immediately next to Fredericksburg, to say the least. So I'm in the water and it was dusk time and the light from the pier is shining through. And I saw these beautiful creatures, a whole bunch of them. And they must been only -- thank God they weren't 500 pounds. They probably were about a foot and a half, maybe, in diameter.

  • 11:50:10

    BOBBIEAnd I picked one up. I put my hand down and I touched it at the pod, not where the middles were -- and I didn't even know what they were -- were hanging down. And it felt like a little spongy kind of a thing. And I thought they were absolutely beautiful. And when I went back to my family and told them what I had done, they said, are you crazy? You could have gotten stung. And now I wonder, oh, I don't think I would have picked it up if it had been any bigger than what it was.

  • 11:50:37


  • 11:50:37

    BOBBIEBut they were absolutely beautiful.

  • 11:50:39

    REHMWell, they are beautiful, aren't they, Jack.

  • 11:50:43

    COVERThey are. And the species you may have seen may have been a moon jelly, the genus Aurelia, which has some tentacles, but they really will not penetrate the callus part of your hands. If they were on a more tender spot of your body you might feel a slight sting. So not all jellyfish sting and, like I say, the Comb jellies don't sting at all. But however, if you were in Australia they probably would not have been a good thing to do.

  • 11:51:10


  • 11:51:10

    COVERThere's jellyfish there that, basically, are incredibly toxic. We don't quite understand why the Box jelly, for example, is so toxic. Since they're feeding mainly on plankton and small fish, it's like going squirrel hunting with a nuclear cannon.

  • 11:51:25

    REHMAnd, Lisa, as director of the Australia Marine Stinger Advisory Services, talk about that, in Australia and the number of people unknowing, perhaps, who are stung.

  • 11:51:44

    GERSHWINYeah, well, it's a very serious issue. In Australia we get about 100 hospitalizations a year from what are known as Irukandjis, which are a very strange group of box jellyfish. There's about 14 different species that we know of, so far. And, you know, they range in size from the size of your pinky fingernail, to the size of take-away mocha, you know. So they can be quite large, but most are quite small. And they are highly toxic. They can be deadly. And, you know, it's a very serious issue.

  • 11:52:16

    REHMEven the very tiny ones?

  • 11:52:20

    GERSHWINYeah, particularly the small ones. You know, you don't even feel the sting most of the time. They're so small and so minor and so insignificant in so many ways. But then…

  • 11:52:30

    REHMSo who's going into the water in Australia, if you can't even see these little suckers?

  • 11:52:37

    GERSHWINWell, luckily, they're only around under very specific conditions, a couple of days a year. And the trick, of course, has been to work that out.

  • 11:52:47

    REHMI see.

  • 11:52:47

    GERSHWINI’m glad to announce that the CSIRO, which is the commonwealth scientific organization in Australia, has actually worked out the model to predict these things. I should also say that they're not only in Australia. Irukandjis occur from as far north as North Wales in the United Kingdom.

  • 11:53:08

    REHMI see.

  • 11:53:08

    GERSHWINTo as far south as Cape Town. And we get stings every year in the Caribbean and Florida, Hawaii, Japan, Thailand.

  • 11:53:17

    REHMSo they're clearly migrating.

  • 11:53:20

    GERSHWINI don't think they're migrating. I think they just haven't been recognized.

  • 11:53:23

    REHMI see. And you're listening to "The Diane Rehm Show." To Cincinnati, Ohio. Austin, you're on the air. Austin, are you there?

  • 11:53:36


  • 11:53:37

    REHMHi, there. Go right ahead, sir.

  • 11:53:39

    AUSTINGood afternoon.

  • 11:53:40


  • 11:53:41

    AUSTINI had a small comment and question. There seems to be a lot we could learn from the water life around us on Earth. And earlier you were discussing some unique traits of certain jellyfish. And I was wondering if your panel could illuminate for your audience a certain jellyfish called the immortal jellyfish. It's scientific name is Turritopsis nutricula.

  • 11:54:13

    REHMAll right. Bill Dennison?

  • 11:54:17

    DENNISONOne of the bizarre lifecycles of jellyfish, that Lisa mentioned earlier are that they have the free-floating medusa stage, the one that you see in the water. And you have this little sedentary polyp phase, these tiny, cryptic little polyps that are on the bottom. And one of the things that we are concerned about is this term called ocean sprawl. So we're building more structures into the ocean, more piers and more aquaculture pens and more culti-protection (sp?) levees and such, which provide hard substrate, which are good places for these polyps to live and proliferate.

  • 11:54:54

    DENNISONSo we can create opportunities in the coastal region for these jellies to live. And because they have this asexual reproduction, where these polyps can split and divide, they can, quote, live forever. This immortality is…

  • 11:55:13

    REHMI see.

  • 11:55:14

    DENNISON…that it's the same genetic individual, but it's been…

  • 11:55:18

    REHMJust going on and on and on.

  • 11:55:19

    DENNISON…split and split and split. Yeah.

  • 11:55:20


  • 11:55:21

    GERSHWINTurritopsis is different. Turritopsis is actually immortal in itself, so when the medusa dies, instead of just dying and disintegrating and turning to mush, the cells actually reaggregate and form polyps all over again.

  • 11:55:34


  • 11:55:35

    GERSHWINSo it's truly, biologically immortal.

  • 11:55:38

    REHMYeah, and what is the best way to treat a sting? When I was a little girl, they used to take wet sand and put it right on that spot. Is that still the best way to go about it, Jack?

  • 11:55:58

    COVERWell, I can tell you right now a lot of the home remedies for jellyfish stings are more placebo.

  • 11:56:06

    REHMTrying to make you feel better in your head.

  • 11:56:08

    COVERYeah, you hear about the -- and particularly here in Maryland -- the use of meat tenderizer, even urine as a cure for jellyfish stings. And we, you know, had some research at the University of Maryland and a dermatologist there basically found out a lot of these cures really aren't doing anything. When the tentacle comes and all these thousands of nematocysts fire that little harpoon in you, that venom is in your system.

  • 11:56:40

    REHMThat little stinker venom.

  • 11:56:42

    COVERYeah, and so what we really find the best thing to do is to get out of the water. And some jellyfish do have tentacles that are clinging to your leg that you may have the nematocysts that aren't fired off. We don't usually find that with the Atlantic Sea nettle, but basically you just get out and take Benadryl or something like that.

  • 11:57:00

    REHMI see.

  • 11:57:00

    COVERBut there's sprays where you can use that have lidocaine analgesic that will help get rid of the itch.

  • 11:57:07

    REHMAll right. Well, let's hope most of us stay out when the sea nettles are around. Jack Cover of the National Aquarium, Bill Dennison of the University of Maryland and Lisa-ann Gershwin, author of, "Stung! On Jellyfish Blooms and The Future Of the Ocean." Thank you all for being with us.

  • 11:57:34

    COVERThank you, Diane.

  • 11:57:34

    DENNISONThank you.

  • 11:57:35

    GERSHWINThank you, Diane.

  • 11:57:36

    REHMAnd thanks for listening all. I'm Diane Rehm.

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