Warmer water encourages jellyfish reproduction, and they can also better tolerate population crashes because their reproductive strategies are complex and adaptable. Some species of jelly can clone themselves, whereas others reproduce sexually but also have a polyp stage – like corals, with which they are related – that allows large populations of immature individuals to multiply while waiting for the right conditions to mature into adulthood. In these ways, they can withstand impacts that devastate other marine species.
Even the coastal infrastructure we build seems to be working to their advantage. Rob Condon, a marine scientist at Dauphin Island Sea Lab in Alabama, says that the pontoons, piers and even drilling platforms help provide anchors for jellyfish polyps, encouraging local population explosions.
But Condon, who set up a global jellyfish database initiative (the wonderfully named JEDI) to monitor blooms, says that the “jellygeddon” scenario envisioned by Richardson and others is unlikely. Jellyfish blooms are nothing new, says Condon, "4,000 years ago in Ancient Crete, they used to paint jelly blooms on their pottery, and even in the 1920s, media were reporting “unprecedented” numbers of moon jellyfish in Monterey Bay."
The JEDI team of more than 20 scientists has now compiled over half a million reports dating back to 1790, and found "no evidence for a global increase in jellyfish blooms". There are some places that are experiencing a pronounced increase in jellyfish blooms, for example "they went berserk in Japan," Condon says, but the data does not support a global increase.
Gathering data on jellyfish, though, is notoriously difficult. Although 70% of the planet is covered by ocean, we really only have a hazy idea about most of the life outside of coastal or estuarine zones. Jellyfish, which inhabit open oceans and deep waters, are still an enigma in many ways. Monitoring individuals and blooms cannot be done by satellite because they are so transparent, have very low biomass, and often occupy waters below the optical depth for satellite penetration. Even finding polyps and larvae in sea grass is tricky. So, despite JEDI's efforts, no one can say for sure whether blooms are increasing or not.
Dealing with blooms where they do turn up is tricky. Shin-ichi Uye, professor of biological oceanography at Hiroshima University in Japan, has devised an early-warming system, called Stop Jelly, which can predict blooms of huge Nomura along the Japanese coastline up to three months in advance. It may allow fishermen to plan ahead, and perhaps allow patrols to ward invaders off before they cause trouble. The government is providing specially designed layered nets, which snare the jellyfish in one, while trapping escaping fish in another.
But once you trap blooms, what do you do with them? Japanese fishermen initially tried chopping them up in the waters, only to discover that the Nomura's defence strategy is to release its sperm and eggs, thus propagating the problem. In Spain, special jelly patrols were dispatched to fish up huge netfulls of them for burial in landfill.
Condon thinks this is a shame. "It might be a good quick-fix for socio-economic reasons, but we don't know what environmental effects destroying blooms could have," he says. "Jellyfish are an important food source for apex predators, and if we start tinkering with the natural bloom system, we don't know what the ripple-down effects may be." They may even help mix and fertilise the world's oceans, some researchers think.
Perhaps one solution is to sustainably exploit their abundance. Jellyfish do have their uses: in collagen preparations (to treat rheumatoid arthritis, for example), they are popular attractions in aquaria, and their fluorescent proteins have been instrumental in biomedical discoveries.
And, of course, they are a source of food. In Japan and other parts of Asia, jellyfish are dried and chopped into noodle-like strips to be added to soups, for example. Some entrepreneurial Japanese are even making vanilla-and-jellyfish ice cream. Jellyfish are 80% protein and very low in fat, although the high sodium content probably outweighs their health benefits.
So… jellyfish and chips anyone?