By James West
30 June 2014
More than 50 million Americans swim in the oceans every year (there are actual government surveys of such things). So if your summer plans involves stripping down and bathing in the sun and salt water of your dreams, read on, intrepid beach-goer. There's something gooey and stingy that's loving warm waters every bit as much as you are (maybe even more), turning those dreams...to nightmares: jellyfish.
Are there more jellyfish now than ever before?
In some places, yes. One recent University of British Columbia study concluded that "jellyﬁsh populations appear to be increasing in the majority of the world's coastal ecosystems and seas," and blamed human activity for these blooms. The areas most affected are the Black Sea and the Mediterranean, says Lucas Brotz, a PhD student and jellyfish expert at University of British Columbia's Fisheries Center, and co-author of the report.
The influx of jellyfish can cause big problems. In October last year, a gelatinous swarm plugged cooling pipes for one of the world's largest nuclear reactors, on the Baltic coast in Sweden, shutting it down. A swarm hobbled a coal-fired power plant near Hadera on the Israeli coast in 2011. Millions of bulging, translucent creatures descended on popular Mediterranean beaches in April 2013, freaking out the tourists. Jellyfish expert Lisa-ann Gershwin rites in her 2013 book Stung! that jellyfish caused the collapse of the $350 million Black Sea fishing industry in the 1990s. In 2007, a plague wiped out a salmon farm off Northern Ireland.
North America hasn't seen as many jellyfish-related problems as Europe, says Brotz. Although some parts of the West Coast—northern California in particular—have seen spikes in jellyfish populations, "they tend to be smaller species that don't really affect people very much."
Is climate change to blame for the increase in jellyfish?
While it's difficult to trace any single jellyfish bloom to climate change—"It's really tough, there's a lot of noise in the signal," Brotz says—warming oceans appear to be playing a role in the emerging pattern. That's because the warmer the water, the less oxygen it can hold. Unlike other sea life, jellyfish are very good at surviving in these low-oxygen environments, giving them a comparative advantage.
"Warmer water species are going to start to have more and more areas where they can expand their range into," he says. Scientists have already observed this phenomenon in Australia's jellyfish. Brotz expects that in the United States, especially on the East Coast, jellyfish will also begin "showing up earlier and sticking around for longer into the fall."
While jellyfish appear to be really loving global warming, they could also be driving the change, writes Australian scientist Tim Flannery: "Remarkably, jellyfish may have the capacity to accelerate climate change," he writes. "Jellyfish release carbon-rich feces and mucus (poo and goo) that bacteria prefer to use for respiration," turning the bacteria into carbon-making factories, accelerating warming. A gelatinous feedback loop.
But scientists are split over the whether global warming is a dominant factor, and are desperate for more comprehensive datasets to fully understand the dynamic. There's even an interactive website and smart phone apps developed by the Monterey Bay Aquarium Research Institute to encourage citizen scientists to submit their own sightings to help with a global tracking effort.
There are other factors driving population booms, of course, aside from global warming: Over-fishing has also killed off the jellyfish's natural predators: fish. Pollution and ocean acidification may also be playing their parts in this complex story. [more]