Jellyfish Swarms: Our Earth Bites Back

As oceans warm in direct response to climate change, sequestering millions of tons of carbon dioxide and becoming increasingly acidic, jellyfish populations increase, terrorizing swimmers, ocean-sports enthusiasts and fishermen from the Gulf of Mexico to Chesapeake Bay along the east coast of the United States, and from the Bering Sea near Alaska to Australia in the Southern Hemisphere.  

Scientists are just beginning to understand the mechanism, which looks to the untrained observer like a warming earth trying to bite its tormenters back.

The clearest link is temperature. Rising temperatures may prolong the jellyfish's developmental stage, leading many to mature at the same time rather than in stages. This causes the large swarms seen recently in Monterey Bay, the Black Sea and Baja, California.

j2 Warmer water may also increase the food supply, mainly zooplankton and other invertebrates. Scientists already know that rising water temperatures are responsible for some destructive algal blooms like red tides.  

Changing water temperatures may even cause jellyfish to seek new headquarters. "No one has ever seen jellyfish polyps in the Bering Sea," says Lorenzo Ciannelli of Oregon State University.

A report from the National Science Foundation notes that, when distributed according to natural rules, jellyfish are an important step in the ecological ladder. When they run wild, as a result of rising water temperatures, displacement of predators or heightened food supply, they can take over thousands of square miles.

In addition to interfering with swimmers and ocean-sports enthusiasts, and fisherman, jellyfish swarms in recent years have even had the temerity to disrupt seabed mining, desalination plants and ship transport operations. Some swarms have even shut down nuclear plants by clogging the water intake pipes that cool the reactor core - an unexpected form of environmental protest from a member of the marine animal kingdom humans once regarded as an occasional (if lethal) nuisance. To understand the scope of the problem, you can view a flash presentation here.

So what are jellyfish? They are primitive members of the Cnidaria. More than 500 million years old and still not evolved, they don't have nervous systems, stomachs or internal organs. They move through the water by contracting their jellylike, bell-shaped bodies. They reproduce rapidly, up to 45,000 eggs daily for the sea nettle, and they can sting in a microsecond. Some stings, like that of the Chironex, can kill in as little as three minutes. In the Philippines, 20 to 40 people are killed annually by jellyfish. In Australia, the number of deaths from jellyfish used to be one per year, but that number is rising rapidly.

Mature jellyfish range from palm-sized to monsters with tentacles 100 feet long. Some Siphonophores (long jellyfish) can reach a length of 130 feet. A whale averages 110 feet.

Marine dead zones, like the one in the Gulf of Mexico, are home to large numbers of jellyfish, since nothing else can survive there. These dead zones now exceed 100,000 square miles of ocean, providing jellyfish with more habitat than nature ever intended. The mindless jellyfish responds by reproducing in record numbers. It's a negative feedback loop that has caused millions of dollars of losses in the fishing industries of the world, namely the Black Sea ($350 million), the Sea of Japan ($20 million), and Australia, where jellyfish dented the shrimp industry to the tune of $10 million in 2000.

The cause? Monty Graham of the Dauphin Island Sea Lab explains jellyfish swarms as "a symptom of an ecosystem that has been tipped off balance by environmental stresses."

"The exact nature of such balance-tipping environmental stresses may vary from place to place and usually involve unique interactions with local ecology," Graham adds. "But such stresses are often caused by people."

In other words, just as people debilitated by a specific disease (like diabetes) succumb to an attendant illness, like heart disease, so too do ecosystems stressed by excessive carbon dioxide burdens and rising acidification succumb to infestations of jellyfish.

When jellyfish populations explode, they eat all the fish, fish eggs and larvae in the vicinity, and this domination allows them to persist and control an area indefinitely. This situation is currently happening in Narragansett Bay, where comb jellyfish dominate, and also in the Black Sea, where the population of comb jellys rose from nothing to one billion pounds in less than a decade during the 1980s.

Jellyfish are also highly adaptable, meaning they will migrate, or be carried by the ballast water of ships (or the hulls of fishing vessels) into an area and prosper while native species are unable to sustain themselves when faced with the dual onslaught of rising temperatures and a foreign predator. Jellyfish then replace native predators, which move on when human over-fishing depletes their prey. In the end, the parasitic jellyfish, which has only a few known predators (leatherback sea turtles, ocean sunfish, and blue rockfish), is the only winner.

There is, in fact, only one obstacle to jellyfish continuing to breed and take over regional ecosystems. In time, they run out of food. So perhaps the best solution - other than curbing emissions and garbage - is to stop factory fishing of traditional species and start fishing for jellyfish instead.

Anyone have a really good recipe for jellys?

Related Reading:
Ocean Seeding: The Good, The Bad, The Moratorium
Monitoring the Oceans in Peril

Image Credits:
Sleeping Bear


If you see any unhelpful comments, please let us know immediately.

Tim Wilkes (anonymous)

Get real there is no global warming and jellyfish just like el nino comes in phases and yes they cling to warmer waters. Didn't we have the coldest winter and snows well into may this year? No Virginia there is no Gloabal warming just a hoax perpetrated by Al Gore and a bunch of scientists hoping for more grant money because we are in a warm cycle of the sun.

Written in July 2009

Jeanne Roberts (anonymous)

I would say it's a free country and you're entitled to your opinion, if not for the fact that you (and others like you) will be the first to arm yourselves and demand food and water from those more provident when you're proved wrong and global warming takes its real toll.

Written in July 2009

Some Guy (anonymous)

Actually, Tim, that would have to be a hoax perpetrated and perpetuated by the vast majority of scientists qualified to make statements about atmospheric studies, trends, predictions, and the effects of human activity.

Written in November 2010

Thank you, Some Guy. My sentiments exactly.

Written in November 2010

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