Jellyfish are about to take over the oceans! Mass "blooms" will destroy fisheries, clog nuke plant intakes, ruin beaches! Long Island Sound, with its warming waters and high nitrogen pollution, is a prime candidate for the Jellyfish Apocalypse!
Connecticut environmental officials and a Yale University expert say there is no clear evidence that this predicted global jellyfish explosion is happening or will happen in our local coastal waters. In fact, there's a growing debate among marine scientists about whether jellyfish populations really are rising at dangerous rates all over the world.
There is also concern that we just don't know enough about what's happening with these strange, beautiful, gelatinous creatures; either in Long Island Sound or in Earth's oceans as a whole.
There has been a recent flood of ominous jellyfish headlines like, "They're Taking Over," and, "The World-Wide Slime Smackdown," and doomsday books like Lisa-ann Gershwin's Stung! On Jellyfish Blooms and the Future of the Ocean.
The arguments are generally that human-triggered ocean warming, increasing marine pollution and the "industrialization" of our coastlines are creating environments where jellies thrive. In some areas, there have been vast "blooms" of jellyfish that have had a major impact on fishing and other coastal activities, including blocking water intakes for nuclear power plants.
Long Island Sound would seem to have all the characteristics to make it a potential jelly disaster area: documented, long-term increases in water temperatures (which jellies like); high nitrogen levels from fertilizer and sewage runoff (which jellies like); lots of structures (ideal for jelly polyp habitats); and depleted stocks of some marine species such as lobsters and predator fish.
Several studies have found that those sorts of habitat changes — which often hurt other marine species — often favor various types of jellies and their reproduction.
"It does seem like conditions could be right for jellyfish to sort of be taking over the world," says Mary Beth Decker, a research scientist at Yale's Department of Ecology & Evolutionary Biology.
Except that a recent long-term study that Decker worked on found no definitive evidence that jellyfish populations are steadily rising around the globe. She was a member of an international scientific team that collected more than a century's worth of available jellyfish data from 37 regions.
"Overall, we didn't see a linear increase over time," Decker explains. Instead, the research indicated that global jellyfish numbers may be rising and falling in roughly 20-year cycles. And there were some regions where "jellyfish appear to be increasing," she added.
The team's results were published in the January issue of the "Proceedings of the National Academy of Sciences."
Those cautious results have triggered lots of controversy, Decker says. Some researchers, in areas like Japan and the Black Sea where huge blooms have caused serious problems, insist that something new is happening. Other scientists warn there isn't enough good historical or even current information about jellies and their population trends to draw any conclusions.
Long Island Sound may be a prime example of that information gap. "We don't have good numbers about what these jellies are doing in the Sound," says Decker.
Current data on jellyfish in Connecticut's coastal waters comes from the state Department of Energy and Environmental Protection's annual surveys of marine life in the Sound. And the only jellyfish species that's even being counted is the lion's mane (Cyanea capillata), says Penny Howell.
She's a fisheries biologist with the DEEP, and says the reason the only jellyfish being counted is lion's mane is that it's "the only one that would be out in the open water where they'd catch enough of them to make (the count) useful."
Unlike some real killer jellies (you do not want to ever be touched by the "Irukandji," a tiny box jellyfish found off Australia that does hideous things to you before you die), contact with lion's mane tentacles usually only results in painful stings. The lion's mane can be pretty impressive even if it isn't a seriously homicidal jelly: it can reach more than six feet in diameter, with tentacles as long as 49 feet.
Howell says these jellies only started being counted in 1992 — not a long time if changes are occurring over 20-year cycles.
The DEEP surveys involve dragging nets across the seafloor at random locations and counting what is brought up. Howell says the data collected so far on lion's manes in the Sound show "no particular trend."
"It looks like it's kind of boom and bust," Howell says of the jellies being counted year to year. In 1997, state marine biologists pulled in enough of the big jellyfish to count that as "a big year." Then the lion's mane population apparently dropped until 2006-'07, and stayed down till 2009, when the survey found relatively higher numbers.
Howell says indications were that 2011 and 2012 were "low years," and she adds the data from the 2013 survey hasn't been compiled yet.
Decker says those results tally with what she knows about the rise and fall of lion's mane in the Sound. "We have very high years, and years when the jellies are very low," she says. " was sort of a medium year for lion's mane." .
Howell says it appears that the numbers of jellies in the Sound rise and fall depending on how fierce our winter storms are and how many jelly predators are around. A bad winter means that not as many jelly polyps (sort of immature jellyfish that cling to stuff on the sea bottom until they're ready for the "medusa" stage with tentacles) survive.
The DEEP's annual survey is geared toward fin fish species, and doesn't count many of the smaller jellies causing huge problems in other parts of the world.
And some of these troublemakers, like the "comb jelly" (Mnemiopsis leidyi), look like jellyfish with their transparent, gelatinous bodies, but are actually a different species. In some scientific studies, the authors get all ticked off if you try to lump comb jellies in with "true" jellyfish like the lion's mane.
It was the comb jellyfish that devastated Black Sea fisheries and, in 2002, put a serious hit on fishing in Narragansett Bay by scarfing up all sorts of fish eggs and other marine creatures that fish need as food.
Despite the limited nature of the DEEP surveys, Decker thinks "it's great they are paying attention to jellies." She believes that more studies like that will eventually give researchers the sort of accurate, long-term data they need.
"We don't have time data for jellies in Long Island Sound," Decker says.
Without it, there's no good way to tell if the Jellyfish Apocalypse is really in our future.