Why Jellyfish May Become the “Cockroaches of the Sea”

By , November 28, 2012 11:05 am
jellyfish as cockroaches of the sea

Sea Nettle Jellies photo by Cherilyn Jose

While jellyfish (referred to as jellies for rest of this post since they are not “fish”) have been painted by public aquariums to be moving and floating masterpieces, the ocean itself has a different viewpoint on them. If the oceans keep getting polluted and overfished at their current rate, the ocean may soon teem with jellies and little else.

Pollution can be in the form of chemicals, like fertilizers and treated (or untreated in many parts of the world) sewage. Pollution can also be physical, like garbage. Plastic is particularly common, and all sorts of wildlife ingest it. The most well publicized plastic eaters include sea turtles who mistake not only plastic bags for jellies, but any plastic bits floating in the sea, and sea birds who have been found dead with enough plastic in their stomachs to die from starvation. With those predators dead, jellies take advantage of the increasing amount of plankton and they proliferate like crazy.

Plankton are the bottom layer of the food web. Overfishing takes out of the ocean the edible sized fish that eat plankton and other small bait fish. With their predator fish gone, plankton proliferate. Jellies love plankton, and they can easily outcompete any young fish for it. The young fish die without reproducing and therefore do not replace their parent’s generation. The seas would theoretically become empty of anything by jellies.

Off of Japan there has been a lot of overfishing, and Nomura’s jellyfish are increasing at an astonishing rate. They can grow to be 6.5 feet (2 meters) wide and weigh up to 450 pounds (220 kg)! Fishermen pull up nets with nothing but hundreds of jellyfish in them. Many nets break under the jellies massive collective weight, and one boat even capsized from them! The fishermen’s early strategy to get rid of them by slicing them up actually increased the jelly population due to the special asexual reproductive techniques of jellies. A future post will delve into this unique aspect of jellies.

Not all news relating to jellies is bad, as their tentacles have inspired scientists create a cancer detector. Scientists made a long DNA strand that mimics the sticky nature of jelly tentacles. In experiments, this long DNA strand was able to capture 80 percent of the leukemia cells (a kind cancer cell) in the blood used. For more on this, please visit “Jellyfish Inspire Cancer Detector” at the Huffington Post.

Please note that I was unable to write this post from the point-of-view of a jelly, as they do not have brains!

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