The quest to understand jellyfish – DW – 05/06/2024


Jellyfish are one of the oldest organisms on Earth. Massive outbreaks of jellyfish, known as blooms, occur approximately every 10 years. However, it appears to be occurring more frequently in some areas, such as along the coast of Namibia.
But data is difficult to obtain. Jellyfish drift with the current, making it difficult to record them accurately.
Such invasions are usually the result of environmental conditions that lead to a reduction in the number of predators.

“Increased temperatures promote invasion, and at the same time, increasing temperatures makes these organisms grow faster. It reduces oxygen levels, which has a negative effect on fish, but not on jellyfish. That means it won’t affect the jellyfish, which will thrive in the areas the fish were forced to abandon. ”

The invasion has not yet reached South Africa. Chris Lewis is a jellyfish expert who specializes in jellyfish species off the coast of Cape Town. So far, 20 species are known here, including the frilled mouth jellyfish and the poisonous box jellyfish.
Researchers are just beginning to understand the role these invertebrates play in marine ecosystems.

They play a very important role not only as an indicator species of ecological crisis, but also as a prey species as well as a predator in the ocean. Because jellyfish are predators, they actually trap large amounts of carbon in the ocean. And when those jellyfish die, they actually sink to the bottom of the ocean floor. Then, in the next season of wind-driven upwelling, those nutrients are recycled by phytoplankton for growth and the cycle begins again.

There is also much to learn about species diversity. Verena Ras has spent just under a decade of her life studying jellyfish. She hopes to work with other scientists to build a database of the different species found on South Africa’s coast to see if their numbers are changing. But it’s hard work.

“We take a small piece of tissue, we extract the tissue, we take the DNA out of the tissue, and all that’s left is this little solution filled with DNA. Then what we do is extract the DNA. And I can tell you, we’ve probably only looked at about 10% of our collection, and there are already so many. We’re discovering a new species, so this is very exciting for us.”

The more researchers understand about jellyfish types and their numbers, the more accurately they can determine changes in populations and correlate them with climate conditions.
Jellyfish seem to feel at home here, as South Africa’s coast is home to one of the richest species of jellyfish in the world. Approximately 10% of all jellyfish species live here.
You can see many of them at the Cape Town Aquarium. Each species has its own characteristics, some live only in cold water, others only in warm water. Chris Lewis is responsible for breeding them.

“This is a complex and difficult task. Each species has its own parameters. Therefore, some species like to live in warm or cold water for a certain period of time, but their diet changes. Other jellyfish eat There are also jellyfish, so we actually have to constantly grow new jellyfish to feed them. Items whose exhibition period has expired.
The ocean, as well as the flow in the aquarium, are great at keeping jellyfish healthy. But as the jellyfish grow in the aquarium, you actually need to adjust the flow to allow the jellyfish to grow optimally. Otherwise, the jellyfish may become very misshapen, which may cause it to die or die. ”

Many people are fascinated by, or even afraid of, these aquatic “dinosaurs” because many jellyfish are poisonous, but only a few species are dangerous to humans.
Some jellyfish also contain important nutrients such as hyaluronic acid and protein.

…has become a popular food in Asia. However, it is not yet on the menu in South Africa.
Instead, scientists here want to better understand the role of jellyfish in marine ecosystems and how it will be affected by climate change.



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