Words by Titia Sjenitzer
Fancy a swim with Jellyfish? Most people would probably say no thank you to that. Nevertheless, there is a true tourist attraction now at the Salt water lake of Misool Island in Indonesia where you can swim with millions of jellyfish. Luckily these are of a harmless type. However, there is a warning hidden behind this. There is a serious risk that in the future jellyfish might be the only thing left to see in the ocean.
A couple of years ago, a friend of mine, who’s an expert on the impacts of climate change, told me that in a few decades jellyfish will be one of the few things that will still be available to eat, if we carry on living as we do now. It wasn’t one of these slightly exaggerated comments made in a social occasion to stir up a conversation, but a calm, matter of fact, remark.
The thought stuck with me. Since that conversation, several news articles appeared talking about big jellyfish blooms causing havoc around the world, clogging the cooling systems of power stations in the UK and Israel, and bringing fishermen and women in despair as they are replacing the fish, leaving them with only jellyfish in their nets. It intrigued me, what makes jellyfish so special that they are the predicted survivors of an upcoming apocalypse? What makes them the cockroaches of the sea? I started to do some digging…
Jellyfish are one of the most successful organisms of animal life on the planet. Fossil records tell us that they have been around for more than 500 million years, they’re older than dinosaurs and even trees.
Credit: Lisa Beasley
It appears that there are a few interesting things going on with the jellyfish. One is the way they reproduce, some of them are even practically immortal. Another is their resilience to environmental changes, including climate change. That humans overfish their predators is an additional benefit in favour of the jellies.
Immortal Jellyfish
One of the reasons jellyfish are so resilient is because of the way they reproduce. Jellyfish start their lives as larvae, looking for a rock or something to attach themselves to and start their metamorphosis into a polyp. These polyps look quite like a sea anemone. As a matter of fact, jellyfish are part of the same family as sea anemones and coral. At this stage the polyps clone themselves and rapidly create big colonies, which can look like huge shrub bushes. When these polyp colonies start to bloom, baby jellyfish bud from these polyp bushes and become the mature jellyfish (medusa) as we know them. As they swim, these adults release eggs and sperms, which meet each other in the water column by chance, forming a new larva and the life cycle starts again.
Then there is the immortal jellyfish (Turritopsis dohrnii). When it’s threatened, for example by illness, physical assault, environmental stress, or old age, it can turn back into the polyp stage. It forms a new polyp colony and starts all over again. Theoretically it can do this forever. And it’s not just the immortal jellyfish that can rise from its own ashes. In 2011, a marine biology student in China kept a moon jellyfish (Aurelia aurita) in a tank. When it died, he kept the body in another tank. Three months later, a new polyp was growing out the top of the moon jellyfish. This regeneration process has now been found in around five species of jellyfish.
The Aurelia aurita. Credits: Abigail Carswell
Climate Change and overfishing
Apart from their reproduction cycle there are other characteristics too that make jellyfish so resilient. One expert on the topic, Juli Berwald, explains in an interview how both the polyps and the adult jellyfish can survive off a tiny amount of nutrients and oxygen because they are very simple creatures. This is precisely how the oceans are changing due to man-made climate change.
Overfishing and climate change also reduces the number of their natural predators, which allows their population to bloom. Moreover, they can escape into polluted waters, where there is less oxygen, and hide from fish that have a higher oxygen demand .
Lastly, the fact that their two different stages in their life cycle take place in two different parts of the ocean, gives them also extra protection. If one of the ocean areas suffers an environmental or biological impact, the other may be less impacted.
Is there a jellyfish apocalypse coming?
According to Will Locket’s summary in his article on medium, despite these advantages that jellyfish have, there is no water tight proof that the jellyfish will trigger an full blown oceanic extinction event. However, he says, don’t let the lack of evidence lull you into a false sense of comfort. We know that our actions could cause jellies to dominate the oceans and we also see several examples of jellyfish blooms already causing serious problems.
This is just one more example of how the complex ocean ecosystem is already being impacted by the changes to the climate that are taking place. There are many ways that a warm and acidic ocean and all other consequences of climate change will reduce the quality of life on our planet, some are more straightforward, others even the best scientists can’t predict yet. Keep following our blogs and social media for more stories about people that are working on climate solutions and suggestions on how you can play your part.
Credit: Lisa Beasley
about the author
Titia is a sustainable oceans advocate. She is a passionate sailor and sustainability professional and Titia cares deeply about the role of the ocean in climate change. As blogger for Divers for Climate, she likes to create more awareness about the power of the ocean as a climate solution. Titia has worked on sustainability solutions across different sectors, including the tourism, fisheries, finance, and food industry. Keen to learn more about all the crazy life that is out there in the ocean, and all the inspirational people that are working to protect it, she will be sharing this journey with you.