Are jellyfish going to take over the ocean?

An interview with jellyfish expert Lisa-ann Gershwin

Jellyfish have been around for half a billion years, and they're flourishing. While beautiful, they pose a tremendous threat to people and property, and warming waters are helping spawn enormous swarms. Lisa-ann Gershwin has studied jellyfish for two decades, discovering more than 200 new species. She recently sat down with Nexus Media to share insights from her research and discuss her new books, Jellyfish: A Natural History and Stung!: On Jellyfish Blooms and the Future of the Ocean.

Lisa-ann Gershwin
Lisa-ann GershwinCarl Berggren

What impacts are jellyfish having around the globe?

The thing that grabs me the most is how something so diaphanous, so brainless — so incredibly, unbelievably simple — can cause so much devastation and so much death and so much harm.

Back in 2004, I was featured in a 60 Minutes episode and they brought a woman who's partner, Robert King, was killed by a jellyfish. (The species was named Malo kingi after him because of the incredibly positive effect on public safety that followed from his sting.) I handed her the specimen, and she just looked at it and looked at it. It was heart wrenching. You could see her looking at this little blob of nothing and thinking, "This thing took away my future. It took away my partner, the love of my life. How did that happen?"

Jellyfish can disable American supercarriers, disable power systems, capsize trawlers, flip ecosystems into completely different states, and it often leaves me feeling, “How did it happen?”

Catostylus is a particularly troublesome jellyfish genus. These animals are notorious for having clogged the U.S. nuclear supercarrier U.S.S. Ronald Reagan.L. Gershwin

Jellyfish have been on this planet for more than half a billion years, and during that time the planet has changed dramatically. How do jellyfish adapt to such diverse environments?

It's amazing. In Stung!, I talk about how jellyfish have been around for so long. When you look at other things, like arthropods, there is unbelievable diversity — literally millions of species. They go from ocean dwellers to crawling through cornfields, they burrow and they swim. Arthropods have dealt with environmental changes through time by evolving into different forms and handling different habitats and different niches. They have diversified.

Jellyfish have not. They’ve adapted by being so unbelievably “plastic,” so flexible in their lifestyle that they can handle nearly anything. Some can stand water that’s drinkably fresh to water that’s hyper-saline, or water that’s not freezing, but damned cold, all the way to warm. They can stand fully oxygenated water or where oxygen is sparse. Plentiful food to months with no food.

Turritopsis lata is an attractive, tiny jellyfish.L. Gershwin

They’re clonal, so looking at a bloom, a fair few are actually clones of each other. They’ve dealt with environmental change over time by doing what they do. They’re so incredibly variable that they just go with the flow. Jellyfish don’t have brains or blood or bones, and yet they move, they swim, they have muscular action that appears to be reacting to something for some purpose. There’s no face and no brain, and you look at them and think, you’ve got to be kidding to me — they don’t seem real to us.

And they’re also beautiful. They’re colorful and they are flowing. And like cockroaches or dandelions, you can’t kill them. Whatever you do, it just bothers them. When you get into that pest realm, how pests survive in their world, it’s because they’re so damned tenacious, and impressively opportunistic. We think the freshwater species even get around on birds’ feet, believe it or not. They’re built for surviving. They’ve evolved that way.

rainbow jelly
Leucothea filmersankeyi is commonly known as the rainbow jelly.L. Gershwin & M. George

You've discovered 200 new species of jellyfish — what does that say about diversity?

I can honestly say, with my hand to my heart, we definitely have not found all of the species. Not just jellyfish, but species in general. It’s estimated we know around 10 percent of the Earth’s flora and fauna, though with jellyfish it’s maybe a bit more unknown.

Where I live in Tasmania — on the southern end of the southern island of the southern coast of the southern continent — there hasn’t been a lot of jellyfish research. When I go out to the jetty about 50 yards from my office and throw a net in the water to see what’s around, about 9 of 10 times I find something new to science.

A jellyfish of the genus Pelagia. This animal is responsible for many millions of dollars in losses to salmon farms in Scotland and Ireland, and the main stinging threat in the Mediterranean Sea.L. Gershwin

It’s not only the species, but everything about them — their biology, their ecology, everything that goes with that identity. Pick any animal or tree, and think of everything conceivable that we could know about it, and multiply that by the millions of species that we don’t even know.

And people discover new species every day. A colleague of mine in Australia has discovered 4,000 new species of sponges. Four thousand. People think we know everything about science and everything about the ocean, that we need to travel to Mars to discover anything. I'm intrigued with Mars just like everyone, but we've got amazing things to discover right here on Earth. Especially ctenophores. I look at them and just think, "Alright, evolution does have a sense of humor . . . how the heck did that happen?" You've got jellyfish that look like belts, others that look like Klingon attack vessels.

Carukia barnesi is one of the more dangerous jellyfish. It can make human victims extremely ill, and sometimes it kills them.L. Gershwin

If people fail to cut greenhouse gas emissions and carbon pollution, acidification and warming will get even more out of hand. What will the future look like for jellyfish?

That’s not the $64,000 question but the $64 trillion dollar question.

Going back over the last couple decades, there’s been an increasing flurry of attention to reports of jellyfish behaving badly, but also a more scientific approach. There have been ecological surveys, laboratory experiments, and computer simulations of different scenarios, and we’ve come to a really good understanding about jellyfish and how they bloom into superabundances and how they tip the balance in ecosystems and essentially take over. We have a good idea of how and where, but there have also been studies that say we don’t have enough data to conclude they’re taking over the world, so slow down.

I’ve been an active player in this to-ing and fro-ing thing, vitally interested in it, it keeps me up late at night and up early in the morning. What does our future look like? I have many years ahead of me, so I’m very intrigued with this question. Are we facing a more gelatinous future, or not? And everything is pointing to yes.

The Porpita porpita jellyfishL. Gershwin

I respect reports that suggest there’s a lack of evidence, and that’s true because there’s a lack of global sampling and a lack of long-term datasets. Humanity never imagined that jellyfish could be a problem. But we do understand the mechanisms for how they bloom, and we’re working on understanding what the tipping points are. And that’s pretty scary.

I tried to wrap my head around it in Stung!, but it's so hard to believe that the things we're doing with such gusto are screwing us so badly, and we don't care. Certainly jellyfish aren't the only manifestation of that, but they are a very visible indicator because they come from left field — they are a completely unexpected player in that system. We think we've got climate change figured out and what effects will happen, and when. We have a reasonable range of scenarios for what's probably coming. But now you have this jellyfish factor that nobody's been considering.

The Spectacularia vanoppenae jellyfishL. Gershwin

Then you’ve got climate warming, which just amps up jellyfish in unbelievable ways. Fractions of degree changes above normal water temperatures amp up their metabolism, they eat more and breed more and live longer — it’s astounding what a little bit of warming can do for jellyfish. Trawling gives them new room for their polyps to settle, and while acidification or chemical pollution doesn’t hurt jellyfish, it hurts everything else like fish and shellfish that struggle with environmental change.

Our impacts are creating tipping points, and once ecosystems have passed those tipping points, they become really stable in their new normal. Once jellyfish take over an ecosystem — or any pest for that matter — it’s hard to undo that. Pest controlled ecosystems are some of the most incredibly resilient ecosystems around: think of cockroaches in your kitchen or dandelions in your garden, pests are tenacious by their very nature. The best way to fix this is to not let it happen in the first place.
