Attack! Jellyfish are taking over the underwater world


First aired on Quirks & Quarks 08/06/13

Jellyfish, those brainless, glowing invertebrates of the water, are taking over the oceans and seas of the world. In a new book, Stung! On Jellyfish Blooms and the Future of the Ocean, leading jellyfish expert Dr. Lisa-Ann Gershwin warns that the creatures are becoming the "middleman of destruction" of ecosystems.

In a recent interview with Quirks & Quarks, Gershwin told host Bob McDonald that most marine species suffer as a result of harmful human activities such as overfishing, pollution, acidification and climate change that damage ocean ecosystems. But jellyfish actually thrive in these damaged waters and multiply at a rapid rate, just like weeds. "Jellyfish really are the perfect marine weeds," she said. "They can grow fast, they are opportunistic, they can eat very little, if there is no food available they slowly just de-grow...they can clone in 13 different ways and at least one species is truly biologically immortal."

Jellyfish are unique because they have a knack for dominance. "They do what we call a double whammy (very scientific term there). What they do is they eat the eggs and the larvae of other species, but they also eat the food of what the species would eat" Gershwin said. This double whammy becomes especially dangerous when ecosystems are vulnerable. Jellyfish are actually capable of wiping out an entire food chain and are a threat to most species, even whales. "You wouldn't think that jellyfish could compete with whales but they do, because they eat the things that other things higher on the food chain rely on."

This may make it sound like these brainless creatures have a plan for taking over the world, but it's not actually their fault that that their domination is spreading. Gershwin points out that they don't actually get out of control on their own. It's only when an ecosystem is damaged that the jellyfish take over and make things even worse.

According to Gershwin, we should see jellyfish as a warning sign of what happens when we interfere with the environment too much, rather than as an enemy per se. "They're an indicator that something is out of balance," she said. "So they're kind of the canaries in the coal-mine if you will -- except whereas a canary dies when something is wrong, a jellyfish flourishes when something is wrong." If we keep heading down the path that we are on, she warned, there will be more and more jellyfish in the oceans.

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