Jelly blooms - Will you be eating jellyfish burgers in the future?

No brain, delicate enough to be killed by a bubble, bad swimmers, and... taking over the ocean? Jellyfish, on the surface, may seem like an unlikely set of creatures to be concerned about. Yet in recent years, jellyfish have become a huge problem in certain parts of the world, clogging fishing nets, shutting down power plants, and stinging vacations swimmers. While there isn't solid proof that the number of jellyfish is increasing globally, there has been a dramatic increase in specific regions, leading to concern that the future of the oceans may be gelatinous.

Cnidarians - Wikimedia Commons

Jellyfish fall into two separate groups: cnidarians and ctenophores. Both groups have bodies that are gelatinous, are generally poor swimmers, and filter feed. The largest difference between the two groups is that cnidarians have long tentacles with stinging cells. These are the ones you want to avoid when swimming. Ctenophores, also known as comb jellies, are harmless and can't sting. 

Ctenophors, or comb jellies - Wikimedia Commons

But why are animals that can't swim and that have such delicate bodies doing so well when so many species seem to be struggling? It's because jellyfish are what we call generalists, organisms that can live in a variety of places and eat a variety of food sources. Jellyfish do well when other species have trouble. Many species need just the right combination of temperature, oxygen, light, and even salt in the water, but jellyfish are resilient to these changes. We are also giving jellyfish a leg up. Humans frequently fish for species that eat baby jellyfish, meaning more baby jellies survive. Finally, with seawater getting warmer, jellyfish reproduce faster. In general, when humans throw a coastal ecosystem out of whack, jellyfish are the ones to remain, and not just remain but thrive. 

These jellyfish can be a menace of the seas for a number of reasons:

1. They cause emergency shut downs in power plants, even nuclear ones. A lot of these power plants take in seawater to cool off the machinery. When the water is too full of jellyfish, it clogs up the entire plant, putting it in danger of overheating and making it necessary to close the plant until the jellyfish can be removed.. This can cause power outages in the region and ultimately costs a lot of money.
2. Jellyfish wreak havoc on fishers. They clog up the nets, sometimes so densely that the nets will break, and even sank a 10-ton fishing trawler in Japan. Jellyfish also eat baby fish, meaning that once there is a huge bloom of jellies, fewer fish make it to adulthood. Even if the nets of the fishers weren't entirely clogged with jellyfish, at this point there would be fewer fish to catch.
3. Jellyfish can get in the way of tourism. Nobody wants to go swimming in waters where they are likely to get stung.
4. A large presence of jellyfish can actually suffocate other animals. Jellyfish need less oxygen in the water than most species of fish. However, when jellyfish die, especially en masse, their bodies are decomposed by bacteria, which use up the oxygen that is in the water. This leaves little for fish to breathe, making water inhospitable for animals besides jellyfish and bacteria.

Massive blooms of giant jellyfish used to be rare. According to Shin-Ichi Uye, in Japan, where blooms of giant jellyfish have brought global attention, there used to be a massive bloom of jellyfish every 40 years. In the early 2000s, however, a massive bloom happened in 2002, 2003, 2005, 2006, and 2007. This particular species of jellyfish, Nemopilema nomurai, is massive: they can grow to be 6 feet wide and weigh over 440 pounds each! The fishing industry struggled as a result. In 2005 alone, fishers filed 100,000 complaints about the jellyfish. What did they think the cause was? Japan blamed it on water running into the ocean from China, bringing nutrients used for farming into the water. This could cause algae blooms and low oxygen conditions that jellyfish thrive in while other species suffer. Luckily for Japan, there haven't been huge blooms of jellyfish in recent years, but the experience was enough to leave people nervous.

Nemopilema nomura, the giant jellyfish sinking boats in JapanWikimedia Commons

Japan isn't the only place to see an uptick in jellyfish blooms. There have been problems in the Black Sea, in the Mediterranean Sea, and in many east Asian waters. Most of the places that have the most trouble with jellyfish blooms are the ones where there is the most human impact, meaning humans fish more there, there is more nutrients in the water from farming, there is more construction, and there are more non-native species that are brought to these waters, often the offending jellyfish themselves. But are jellyfish increasing globally? If waters get warmer, have less oxygen, and become more acidic, all things that we see happening, doesn't that set the stage for an ocean dominated by jellyfish?

Jellyfish and roast duck salad
Wikimedia Commons: Credit Line

Maybe. The problem is that jellyfish populations tend to fluctuate over the span of many decades. If the number of jellyfish fluctuate in a pattern every 40 or 50 years, you need a record of jellyfish that is at least 40 or 50 years long to say anything definitively, and in most cases we just don't have that. But with all the changes we see happening to the ocean, it is entirely possible that we will see more frequent, larger blooms in many areas.

So what can we do besides reduce pollution and do what we can to slow climate change? The answer may sound familiar; it is often a proposed solution when an animal takes over an ecosystem. We could eat them. In fact, in order to tackle a troublesome surplus of jellyfish in the Mediterranean Sea, there has been an effort to get Europeans to eat jellyfish. Chinese and Japanese cultures already embrace eating jellyfish. If life gives you lemons, make lemonade; if the ocean gives you jellyfish, make jellyfish burgers.

Venom with a voracious appetite - The lionfish you should eat

I'll never forget the first time I saw it in the wild. I was snorkeling off a pier in Vieques, Puerto Rico. The sunlight flickered underwater as the breeze rippled the waves. With a net in one hand, a nervous tremor disguised by the movement of the waves, I searched for a flashy fish with venomous spines and a voracious appetite. The lionfish is boldly striped and has long, spiny fins poking from almost every direction. For such a dramatic looking animal, the lionfish was proving tricky to spot. Then my boss pointed under a ledge, and there it was, hidden in plane sight in a way I thought impossible. That's the thing about the lionfish. There is nothing subtle about this species, from its appetite to how it stings to how quickly it reproduces, and yet it has a way of making itself at home in places it definitely doesn't belong. 

If you're wondering what an invasive species is, chances are you have already encountered one. An invasive species is anything that is in a land that it isn't native to that is also wreaking havoc on local plants and animals. In New England, we have the beautiful Oriental Bittersweet which strangles local plants and trees. In the south, Kudzu vines cause similar damage. If you've ever been told to wash off a boat before putting it in a reservoir, it may have been to stop the spread of the infuriating zebra mussel. The Asian longhorn beetle is the reason you can't bring firewood across state lines in New England. We are surrounded by invasive species, but in this long list of rabble rousers, the lionfish stands out.

The predominant theory as to how lionfish came to the Atlantic is that they were released from home aquariums when they got bigger than the owners expected. This is a common story. Finding Nemo may show the happy little fish who manage to escape from a tank into the ocean, but when this happens in reality, the results are quite different. Released animals usually die out in a habitat they are ill suited for, either freezing, starving, or being eaten. But every once in a while a species will find that the environment was practically designed for them to thrive. What follows is nothing less than madness. The video below shows a time lapse up until 2010, showing how quickly lionfish spread through the US and the Caribbean.

Why didn't the lionfish die out when released into an ocean where they were never meant to be? One reason is that they don't have natural predators in Atlantic waters. While sharks, groupers, and barracudas can be trained to eat lionfish and have been spotted doing so, lionfish are not their preferred food.

In addition, lionfish seem to be able to live just about anywhere. I saw lionfish in Belize less than 4 feet deep, but they have been spotted shipwrecks up to 300 feet deep. Most fish are constrained by the kind of water they can live in, but lionfish get around this. An inquisitive 12-year old girl from Florida found that lionfish can survive in water that barely has any salt in it, teaching us to never underestimate both lionfish and young girls.

So they survived, but why do they continue to spread? Have you heard the phrase "mate like rabbits?" We should change it to "mate like lionfish." While a lot of native fish can't reproduce until they are about 3-5 years old, lionfish can mate after just one year. A female lionfish is a mating machine; she can reproduce every 4 days, making a whopping 2 MILLION eggs per year! That's a lot of baby lionfish.

All those fish need something to eat, and that is where we run into problems. Lionfish are voracious feeders. When lionfish are introduced to a coral reef, they can eat 90% of the baby fish in a reef in just five weeks. No baby fish means few adult fish. This is bad for reefs, and this is bad for fishers that rely on fish for their livelihood.

The stomach contents of just one lionfish. That's 21 fish swallowed whole.
 Credit: USGS

These hungry fish are fast. Given the chance, the lionfish would eat Nemo before he knew what hit him.

There is hope, however. If there is one thing humans are great it, it is collecting astonishing numbers of fish from the ocean. Fishers are catching this fish and selling it to restaurants which sell it to hungry tourists and locals alike. The venom in the spines is neutralized by heat, so once the animal is cooked it turns out to be a tasty treat. The spines are even used to make jewelry. These aren't just cool ideas for making the best of a bad situation; these are solutions that are both making people money and having an impact.While it may be impossible to eliminate the lionfish completely from the Atlantic, keeping it in check helps local fish and local people.

So what can you do? Support these efforts. If you travel anywhere near the lionfish invasion, try the fish! It's a delicious, flaky white fish which is suitable for a wide range of dishes, from fillets to ceviches. Buy lionfish jewelry if you come across it. Continue to create a demand for this invasive species and people will continue to provide it. But also remember why we have a lionfish problem in the first place. The next time you have to wash off your boat or buy firewood a mile down the road from camp, be thankful people are doing what they can to stop invasive species.