Climate Change and the Scary Jellyfish Scourge

By Andrew Freedman, Washington Post
August 3, 2009

This summer has seen its share of odd climate change-related science stories. A running theme has been changes in the size and abundance of species as a result of human activities. For example, in June it was reported that jellyfish are becoming more numerous and larger in size, and they may soon "rule the ocean," while in July we learned that some creatures on land – sheep – are shrinking in size due in part to warming temperatures.

Try as I might, I can’t seem to shake my nonplussed attitude towards the sheep story, since sheep are so docile that even a gargantuan sheep would fail to scare me, and the idea of tiny sheep is more cute than worrisome.

The jellyfish story is different, however.

In June I came across a Discovery News/ABC Science Online piece about a new study reporting that jellyfish are taking advantage of decades of overfishing and rising water temperatures to expand their numbers, range, and size. Then last week National Geographic News and other outlets reported that Japan is gearing up for an invasion of previously rare giant jellyfish, known as Nomura, that can weigh as much as a sumo wrestler.

Let me repeat that. There is a jellyfish that can weigh as much as a sumo wrestler, between 400-500 pounds.

Jellyfish have always unnerved me, with their transparent appearance and odd shape that makes them look more at home in the outer solar system than here on earth. When concerning government activities, transparency is a good thing that can increase confidence and reduce fears of abuse of power. But in nature, transparency can be deceiving. I just can’t trust a transparent sea creature. The very fact that they appear to have nothing to hide means that they must have something to hide. (Nor can I trust transparent food, and I have always had issues eating JELL-O).

The fact that many jellyfish species are highly venomous doesn’t help their case. A Portuguese "Man-of-War" once terrorized my family after my mother plucked it up off a beach in Bermuda during a vacation, intending to show it to my brother and me. Recalling the pain, she still ranks it as her all-time dumbest move.

My mom was lucky. Some jellyfish actually kill people, which is probably embarrassing for the victims when they arrive at their afterlife destination and have to tell others that their fate was sealed when they encountered a tiny, transparent denizen of the deep.

"Really? You were killed by a jellyfish? As in, a tiny, clear, plastic-lookin’ fella that can usually be avoided while swimming? My God man, that’s more embarrassing than having a spiny coconut fall on your head from a weak palm tree, which is what happened to me."

In some parts of the world, jellyfish are no laughing matter though. For example, when snorkeling at The Great Barrier Reef in northern Australia last winter (summer in the S. Hemisphere) I had to wear a full body protective wetsuit to prevent being stung by the dreaded irukandji jellyfish. When I asked some Aussies how I would recognize one when I see it, they told me they are too small to see, and the only sign of one would be unbearable pain followed by death.

"Oh, ok, that’s very helpful," I said. "Thanks. I’ll keep ya posted then."

There have been reports of increased jellyfish sightings and stings at local beaches as well, including a story in July about a spike in jellyfish stings at Dewey and Rehoboth Beaches in Delaware. More than 100 people were stung in one week in July, compared to the normal of 30.

So what’s going on? According to the Discovery News piece, climate change has warmed the global oceans enough to allow jellyfish populations to grow, while overfishing has eliminated many of the fish that have competed with jellyfish for the same food sources. As previously reported, global ocean temperatures were the highest on record for the month of June, according to the U.S. National Climatic Data Center.

The scariest sentence in the Discovery News piece pertained to this conflation of trends in ocean temps and overfishing: "The team believes that for the first time, water conditions could lead to what they call a "jellyfish stable state," in which jellyfish rule the oceans." According to the study discussed in the article, jellyfish can even survive low oxygen "dead zones", such as the Gulf of Mexico dead zone, whereas fish cannot.

Wait a second. Technically speaking, if jellyfish can survive in a "dead zone", doesn’t that make them… undead?

Great, now I am even more scared than I was when I started writing this piece.