We spotted every kind of jellyfish

Under jellyfish Encounter with the crush

The Loro Parque in Tenerife. The zoo is expected to attract more than 40 million visitors every year. In the middle of the green, behind the keas, there is a pavilion. From the outside it looks inconspicuous. But anyone who enters this dark room, in which only the aquariums shine, is fascinated. Jellyfish float in each one - in green, blue, pink, white ... graceful beings like from another world.

Jennifer Purcell: "Here we have Aurelia aurita." Common moon jellyfish that children play with on the beach. Pulsating bodies that glow magically green in artificial light. Jennifer Purcell: "Back here we have one of the key species, the luminous jellyfish Pelagia noctiluca, which causes terrible problems in the Mediterranean because it burns badly."

Jennifer Purcell is also only visiting Loro Parque. This is where the jellyfish polyps are bred, which she uses to advance her research at the University of Las Palmas. "The field was very small. For decades, decades in fact, we've been telling people that jellyfish are important. But nobody really cared."

But then the incidents increased: jellyfish clogged the cooling water inflows from power plants. Or in 2007, when a school of fish struck salmon farms in Northern Ireland and killed all the fish in just seven hours.

Millions of jellyfish in just one school

For Jennifer Purcell, the change in mood is gratifying after decades of struggling to get funding for her projects and ship time. Modern laboratory analyzes and high-performance cameras that record what is happening underwater, meanwhile, allow completely new research approaches. And it can be used to address questions that appear trivial at first glance - but are by no means. For example, how many animals actually make up a swarm.

Jennifer Purcell: "So I got a really great chance to study a moon jellyfish bloom in the Northwest Pacific, in a fjord in Washington State." There, in Puget Sound, there is great fear for the valuable wild salmon population. Jennifer Purcell: "It has been flown there month after month for years, and the swarms of jellyfish can be easily identified and quantified on the aerial photographs."

The flights reveal to the fishery biologists that the salmon's prey - herrings and smelts - are more likely to be found in the rural part of the inlet, while the hundreds of meters long, white stripes of the jellyfish schools can be found closer to the big cities. But the aerial photos only show what is going on on the surface.

In order to see below the water surface, plankton nets equipped with a camera were used. Whenever they came on board, the nets were full, water and long threads of slime dripped from them: they were full of moon jellyfish, which Jennifer Purcell quickly counted and measured. "We tried to make the best possible estimate. We looked at a place where the Puget Sound is only ten meters deep: and there were millions of jellyfish there."

Millions, in one swarm. Jellyfish have populated the seas for eons. Its blueprint seems to have changed little in more than 600 million years. Two transparent layers of skin with a gel in between. They have neither brain nor blood nor heart. Basically just skin, stomach, mouth; and a network of nerve cells. They have developed an astonishing variety: there are state jellyfish up to 50 meters long in which polyp sits next to polyp.

There are filter feeders the size of a fingertip, as transparent as glass, and giant predators, with bodies in which a human would disappear and tentacles longer than a blue whale. What they all have in common is that they grow very quickly because they do not build up any solid tissue: They consist of more than 95 percent water. The ancient jellyfish were the first to rely on this evolutionary recipe for success. But later animals from very different tribes followed suit: there are the barrel-shaped salps, which are related to vertebrates. And the transparent rib jellyfish, which are still debated about where they actually belong.

"There have been invasions of alien species"

Some of the jellies live alone, like a nameless, brightly shining jellyfish that marine biologists have discovered at the bottom of the Mariana Trench. Others gather in gigantic swarms. They seem to have been increasing around the world since the end of the last century. In 2009 an article entitled "The Jellyfish-Joyride" was published in the journal Cell, "Die Jellyfish-Joyride":

The researchers warned that humans could damage the oceans so severely that they will be ruled by jellyfish in the future. And so marine biologists try to find answers to open questions. About what is actually normal and what signs of a profound change in the seas. Are the jellies really on the rise?

Larry Madin is the associate director of the Woods Hole Oceanographic Institution in Woods Hole Massachusetts. And he is also a member of the small group of researchers who are dedicated to the gelatinous zooplankton.

"In the past there have been outbreaks in the Mediterranean region and there have been invasions of alien species. In the Black Sea, for example, the population of a comb jellyfish exploded, which was probably brought in by ship with the ballast water and which caused enormous damage to the fishery." The mnemiopsis, no more than finger-long, ate its way through the plankton in the Black Sea within a few years until the sardine stocks collapsed.

"We see such invasions in other places as well, sometimes because the animals are introduced, but sometimes also because the water is getting warmer due to climate change and thus offers the jellies better living conditions, but the fish worse. The stocks can also be found in the Areas explode where we are taking jellyfish food competitors out of the system through overfishing.

We also see that they feel comfortable in the 'dead zones', for example in the Gulf of Mexico, where the overfertilization has made the oxygen content in the water too low for fish. The jellyfish don't mind. On the contrary: it gives them the opportunity to build up their stocks. "

Jellyfish bloom depending on the position of the sun?

But it is not easy to predict the development of gigantic jellyfish explosions. Example: Eastern Bering Sea. There, during the 1990s, it looked as if the jellyfish were taking over the ecosystem: They multiplied and multiplied. Until 2001, when the population collapsed and has remained at a moderate level ever since. In 2001 it suddenly got warm in the Bering Sea, and that changed everything: currents, water layers, wind ... The pollack larvae also suffered, and so there was no longer enough to eat for a jellyfish party.

In light of such findings, researchers at the University of North Carolina at Wilmington became interested in what data actually support the assumption that jellyfish are taking over the stressed seas. They analyzed the database - and found that it is far too sparse for far-reaching statements: a global increase cannot be proven with it.

Jellyfish blooms are interesting - but first of all, a natural process that has been going on for hundreds of millions of years. Kylie Pitt: "We know that because the impressions of their carcasses have been handed down in fossil form."

Jellyfish consist of 95 percent water, skin, stomach, mouth - and a network of nerve cells (picture alliance / dpa / Stefan Sauer)

Whether the jellyfish blooms are increasing or not, the final judgment is still pending for Kylie Pitts. The ecologist from Griffith University in Brisbane then took a closer look at the existing data. In doing so, she came across an amazing connection:

"There are undoubtedly regions in which the jellyfish blooms are demonstrably increasing. For other regions we also know that the populations are falling. If you analyze all the time series available worldwide, you can see that their population - viewed globally - in a cycle of 20, 22 Years. "

The Australians suspect that there is a complex interplay between the eleven-year sunspot cycle and the eleven-year cycle with which the sun alternates between the north and south poles. The suspicion is that plankton production slackens as soon as the sun is particularly active: less plankton, less for the jellyfish to eat.

As obscure as it sounds, similar phenomena have appeared in some fish and seaweed, adds Kylie Pitt. "We believe that with the jellyfish we are dealing with a natural cycle first, and that we have to work out what additional humans add to this cycle."

Oil rigs, ships: man-made jellyfish farms

Most notorious for their outbreaks are the real jellyfish - from the moon jellyfish to the moon jellyfish. This has to do with the fact that humans have the closest contact with them - but also with their life cycle. It begins as a fertilized egg cell that divides and swims through the water as a larva. The larva settles on the ground and turns into a polyp that soon looks like a pile of plates.

At some point these plates peel off one after the other - and small medusa swim away - to feed and grow. For the cycle to work, the polyps have to cling to rocks and stones - or to a piece of infrastructure that humans build into the sea: every wind turbine, every oil derrick, every ship, every pier helps.

This is the great fear of ecologists that humans will create real jellyfish farms. On the other hand, the scientists only know with certainty where the polyps of the moon jellyfish are located. With everyone else, they have no idea.

Every few weeks, polyps and juvenile jellyfish are packed for transport in the cultivation station at Loro Parque on Tenerife. It is a short passage across the Atlantic to the neighboring island of Gran Canaria. There in the mountains on the outskirts of Las Palmas lies the modern campus university, where we meet again at the Ecophysiological Institute Eomar Jennifer Purcell.

The American is actually doing research at Western Washington University in Anacortes, and she is visiting the Canary Islands with a scholarship. "The importance of jellyfish in the entire carbon cycle is much greater than we realized. It is difficult to determine, and so I would like to learn a technique here that will allow me to gain a deeper insight into their metabolic requirements."

On the tiled laboratory tables, the aquarium next to the aquarium, with sea water flowing through it, which is delivered in canisters. Polyps are growing in some of the aquariums. In others the mini jellyfish are already pulsing.

Daniel Bondyale Juez examines, among other things, in the laboratory how jellyfish adapt to starvation (Deutschlandfunk / Dagmar Röhrlich)

Daniel Bondyale Juez is studying at Eomar. He fishes a young ear jellyfish from one of the aquariums. After starving for almost a month, it has become completely transparent, barely noticeable in the water. "As a result of starvation, she began to digest all the parts of the body that were not absolutely necessary in order to survive despite stress."

And now it is supposed to provide data for science. Measurements are taken in another laboratory one floor higher. The aim is to find out how much food jellyfish and their polyps need in order for their metabolism to be balanced, how they adapt to starvation and what effects this has on their ability to reproduce - important data in order to be able to better assess their role in ecosystems.

Daniel Bondyale Juez carefully maneuvered the jellyfish into the measuring container. She hardly moves anymore. Then he measures the decrease in oxygen in the water. A process that he will repeat at fixed time intervals. Earlier series of measurements had shown that it is not the swimming medusas that consume the most energy, but the polyps. Finally, they multiply intensely, pinching off one mini medusa after the other. The researchers suspect there could be up to 30. Nobody knows exactly yet.

Jellies are always hungry, can devour vast amounts, but also starve for sheer eternity. They devour everything - from microscopic plankton organisms to small fish, and they do not disdain other jellies either: In the Black Sea, a second species of cider jellyfish that was introduced solved the problem with the first: it eats them up. Even cannibalism is no stranger to them. But apart from this, if you will, internal jellyfish cycle, jellyfish were considered a dead end in the food web. At most interesting for a few food specialists like leatherback turtles or the bizarre sunfish.

Jellyfish are on the menu of penguins and whales

Because jellyfish bodies are fragile and lack solid constituents, they instantly turn into unidentifiable phlegm in the stomach of a predator. That is why they were not noticed in the classic analyzes of the stomach contents. But now there are new ways:

"For 14 years we have been developing a method to reconstruct the DNA traces in the faeces." Simon Jarman from the Research Center in Biodiversity and Genetic Resources in Porto, Portugal, studies the ecology of Antarctic birds and mammals. Jellies were not on his research agenda at all - until the DNA analyzes revealed the unexpected:

"We analyzed many fecal samples so that we now have a very good picture of what albatrosses and penguins, but also seals and whales, are eating. An important finding is that many animals in the South Ocean eat jellyfish, especially the fiery jellyfish. who we are most familiar with. They really make up a large part of their diet. "

Not krill or fish, but jellyfish - of all things, the low-energy jellyfish. Moon jellyfish, with their 17 calories per 100 grams, are still the most nutritious thing the gelatinous animals have to offer. A luminous jellyfish has 2.4 calories and a comb jellyfish a meager 1.7. Instead of fat, there is collagen. But maybe it is exactly what the animals are looking for, speculates Simon Jarman: After all, people also eat salad.

"Biologists in such cases wonder whether the jellyfish are deliberately being eaten - or because each predator is taking what they can get. Our results suggest that some penguin and albatross species are generalists: They seem to be eating jellyfish simply because they are there We carried out our investigations at several points around the Antarctic at the same time, and it turned out that they always eat a lot of jellyfish when there are many in the ecosystem. "

Lobster larvae love salps

What role do jellyfish play in the food webs of the oceans? More and more individual findings paint an ever sharper picture. Andrew Jeffs: "What we didn't know: The crawfish and their larvae also eat jellyfish. When crawfish larvae hatch, they fit on the tip of a needle. They then drift through the ocean for two or three years. They are absolutely flat and they look like they have I cut a circle out of a plastic bag and glued ten long legs to it. They are miserable swimmers and as soon as they come across something in the water, they grab it with their long legs and test whether it tastes good. "

Nobody knew exactly what they were eating. Until 2011, when Andrew Jeffs from the University of Aukland found strange prey during a plankton expedition: "On one of these jellyfish, it was a large jellyfish - so in reality it wasn't a jellyfish, but a salp - so ten or 15 were attached to this salpe Lobster larvae that busily ate salp meat while using it as a raft, clinging to these giant gelatinous sea creatures like a small child on a giant ball of cotton candy that it occupies for the next few days.

What we found: The gelatinous plankton - including the jellyfish - make up around 80 to 90 percent of the diet of the Australian lobster larvae. They are quite picky: They love salps and abhor the real, fiery jellyfish. "Even with young tuna and swordfish in the Mediterranean, the gelatinous animals should make up up to 80 percent of the diet.

Penguins also eat jellyfish - when they are around (imago stock & people 65760025)

The Lurefjord north of Bergen in southwest Norway. An idyll, meadows, forest, a small village. In the past, fishermen didn't have to go far to fill their nets with herrings or cod. But the dark gray water has not produced anything since the 1970s. At that time, a couple of deep-sea jellyfish swam over the shallow rock that separates the fjord from the sea one night with the high tide: Periphylla periphylla - bright red beauties that prefer the dark water of the deep sea during the day and come to the surface at night to catch plankton eat. The jellyfish was caught in the fjord, reproduced and made it a dystopian model for the future of the seas, because the fish disappeared.

Instead, the marine biologists came to analyze what was happening there. And again they learned surprising things about the role of jellyfish in ecosystems. It's about the so-called jelly falls: the fate of the dead jellyfish. Andrew Sweetman from Heriot-Watt University in Edinburgh is interested in this. His specialty is the ecology of the seabed, which is why he has been draining camera equipment into the Lurefjord since 2010. Because the jellyfish appear as a dense band on the sonar in this fjord, he actually expected to see the bottom covered with rotting jellyfish.But strangely enough, he hardly saw any. The solution to the riddle came from the neighboring Sognefjord:

Andrew Sweetman: "We sent a lander there with cameras and a fish as bait at a depth of 1,300 meters. The next day we pulled it up again and downloaded the images. We saw that the fish was eating deep-sea scavengers very quickly The next day we repeated the experiment with a jellyfish and expected that nobody would eat it.

To our surprise, 18 hours later when we brought the lander on board, the jellyfish had disappeared. We spent two and a half hours deliberating how to fix it better, assuming it had slipped off. Only then did we look at the video material: And lo and behold, the jellyfish had reached the bottom - and was eaten by the same scavengers as the fish bait in a very short time. "

So should the jellies do their part to "feed the deep sea"? Many more experiments followed, in different water depths and in fjords as well as at 5,500 meters in the western Pacific. The same result everywhere: jellyfish are popular in the deep sea, they create nutrients from the surface downwards. In doing so, they sink surprisingly quickly: every day they descend between 500 and 1,600 meters. When they arrive in the deep sea, they are still undecomposed, fresh meat, so to speak:

Andrew Sweetman: "They feed the animals on the seabed just as quickly as a dead fish would. So jellyfish increase the flow of carbon and nitrogen massively and are an important factor for the biological pump. They are therefore important for the entire community on the seabed , not just for the scavengers. "

Living sensors on the state of the seas

The carbon that is eaten on the deep sea floor does not return to the atmosphere as quickly. Andrew Sweetman suspects that given the masses of jellies in the world's oceans, their contribution to the carbon sink should not be negligible. So far, it has not been included in the model calculations for the buffer capacity of the oceans.

The view changes. Just 20 years ago, jellyfish were considered to be useless bags of salt water, a cul-de-sac in the food web, which ate everything empty, but was no good in itself and was about to take over the oceans.

Larry Madin: "We know that the oceans are changing due to rising temperatures and other environmental pollution. And we also know that some jellyfish can cope better with this than fish."

Nightmarish prognoses provoked martial solutions. Synthetic molecules could prevent reproduction and GPS-controlled robot terminators could chop up the animals. Suddenly money flowed into jellyfish research and with the results the perspective shifted:

Larry Madin: "All these animals, whether they are jellyfish, state jellyfish, comb jellyfish or salps, they are all interesting adaptations to life in the oceans. They can teach us how life in the oceans evolved . They are fascinating beings - and I think they can help us understand how the ocean is changing around us. "

Jellyfish are likely to increase precisely where humans change the conditions - and thus they could become living sensors for the state of the oceans.