What’s going on here?
Rising sea temperatures due to the climate crisis are causing a huge increase in jellyfish numbers. Over the last three months, Costa Brava on the Catalan coast has seen a 41% increase in beach-goers seeking medical attention for the painful stings.
What does this mean?
The Mediterranean has been experiencing a marine heatwave this summer. Heatwaves are defined by an extreme rise in ocean temperature and, this year, the water has been nearly 2 degrees hotter than average. Warm water makes it easier for jellyfish to reproduce, leading to massive numbers invading coastal waters. Especially in the Mediterranean, where jellyfish populations are most commonly found in huge numbers during specific times as “blooms,” rising temperatures exacerbate this phenomenon, leading to even higher numbers.
Jellyfish are very resilient creatures. They are able to adapt well to conditions of low oxygen in water, another side effect of the climate crisis. They can even thrive in poor water quality,meaning they are frequently found in developed coastal areas such as ports and marinas. In fact, these structures make it even easier for them to reproduce by providing a surface for their polyps to settle as they mature.
Why should we care?
All of these factors suggest that our interactions with jellyfish will become more frequent due to the climate crisis. This summer in Costa Brava, the situation has gotten so bad that some beaches have had to close completely. This can have knock-on effects on tourism and how we interact with the coastal environment.
Jellyfish aren’t only a pain for us humans, though. Seas swarming with jellyfish can have complex and adverse effects on the food web. Jellyfish larvae are one of many types of plankton. Their resilience to the effects of the climate crisis means they are dominating over other plankton. A study on northeast Atlantic plankton found that copepods (a type of plankton that grow into crustaceans) are declining, and they are a valuable food source for fish and seabirds.
Jellyfish are a food source for many larger ocean predators, such as sharks, sea turtles and tuna. Reduced numbers of these predators due to issues like the climate crisis and overfishing means even more jellyfish in the sea.
Be curious…!
Like many travellers, if you are heading to the beach this year make sure you take precautions
• MedusApp is a Spanish citizen science app allowing the public to record jellyfish sightings, and avoid beaches which are most impacted.
• The Marine Conservation Society also has its own citizen science initiative to record UK jellyfish sightings.
• Eating invasive species is a common way to counteract the negative impacts on the ecosystem whilst addressing food insecurity. They are commonly consumed in East and Southeast Asia, but check out how some are trying to introduce it more widely as a solution to the problem.
• Check out iNaturalist, where you can learn more about jellyfish and which species sting.
Featured image: Marat Gilyadzinov via Unsplash.
