CHARLESTON — When you step foot in the surf, you run the risk of the sting of sea nettles, sea wasps or other jellyfish.
In fact, alarms are going off that jellyfish swarms are taking over the world’s oceans — starving out food fish, injuring swimmers, overloading the nets and capsizing fishing boats and clogging the pipes to power plants and nuclear vessels. Swarms that sometimes cover hundreds of square miles recently have been reported in many of the world’s prime vacation and fishing destinations, according to the National Science Foundation.
The fear is that warmer waters, overfishing and pollution are depleting other species while giving jellyfish the habitat they need to thrive.
In the Lowcountry, swarms tend to show up in the midsummer heat, when bathers flock to the beach.
In 2010, hundreds of swimmers or waders were stung at Charleston County beaches, and sightings were reported of long-tentacled Portuguese man-of-wars. In 2008, thousands of midsummer sea nettle stings were reported along the state’s beaches.
Pearse Webster, a South Carolina Department of Natural Resources marine biologist, does near-shore trawls in the spring, summer and fall each year for the SEAMAP-SA Coastal Survey. Oh yeah, he sees jellyfish.
In trawls this spring from Georgia to Charleston, “we just had huge catch after huge catch of cannonball jellies. At times the numbers reached a point of overwhelming what we could handle with our nets,” he said.
Year in and year out, jellyfish are densest in the ocean south of Winyah Bay, Webster said.
Smithsonian Magazine, in a 2010 feature, counted the apparent predicament of jellyfish blooms as one of 40 things to know about the next 40 years, suggesting jellyfish might be on their way to dominating the biomass, or organisms in the oceans. The article pointed out that the creatures are reproducing in astonishing numbers and showing up where they had not been seen before.
At least one researcher has suggested that, as reliant as society is on the ocean for food, people better get used to eating jellyfish. And they are edible, a traditional Asian dish. A crop is now harvested off Georgia. Among others who were lost at sea and survived partly by eating jellyfish are two Lowcountry teens who drifted 111 miles in a week in 2005 after their 14-foot sailboat was swept out of Breach Inlet by strong currents.
Monty Graham, senior marine scientist at the Dauphin Island Sea Lab in Alabama, studies jellyfish. The creatures do appear to be increasing in some regions and are causing big problems, he told the science foundation. But jellyfish have lived and likely swarmed in the oceans for at least 600 million years, and the population rise might just be cyclical.
“The jury is most definitely out as to whether this is a global phenomenon,” he said in an email. “The most important thing is that jellyfish are evolutionarily programmed to respond to changes in food supply.” Because food supplies change as climates change, and there’s no long-term data, it’s difficult to tell how long-term the swarms might be.
In the Gulf of Mexico, jellyfish appear to increase and decrease in decadal cycles, he said.
Webster isn’t concerned about jellyfish taking over the Lowcountry ocean — so far, he said. He’s been pulling trawl nets since 1987 and doesn’t see it happening yet. His surveys have kept count of cannonball jellies since 2001, and 2001 had the largest concentration. But the 2010 numbers were close, and the spring counts this year seem to be on track for a record.