We here at Universal Jellyfish have been on top of this for awhile. If people decide to get serious about eating them - that would probably take care of it.
Here is a BBC article with updates:
In the last decade enormous plagues of jellyfish have been taking over the seas. And it is our fault.
As I rose to a couple of metres below the surface, I saw the problem too late: the shallow water was carpeted with mauve stinger jellyfish (Pelagia noctiluca). There was no avoiding it, reaching the surface meant I had to swim through the flames of stingers....
Locals told me the carpet of jellyfish, known as a bloom, was not an isolated case. My dive instructor said he had seen massive blooms off the coast of Gozo every year since 2000. But never before then.
In fact, huge annual jellyfish blooms have been cropping up not just across the Mediterranean, but also the Black Sea, the Gulf of Mexico, and the Yellow and Japan Seas. Is this a bizarre blip in the continually changing balance of oceanic life, or the beginnings of a new state change in marine diversity?Or in other words: in the Anthropocene, will the seas be filled with slime?If they are, we face some serious problems.
Last year alone, nuclear power plants in Scotland, Japan, Israel and Florida, and also a desalination plant in Israel, were forced to shutdown because jellyfish were clogging the water inlets. The entire Irish salmon industry was wiped out in 2007 after a plague of billions of mauve stingers – covering an area of 10 sq miles (26 sq km) and 35ft (11m) deep – attacked the fish cages. Two years later, a fish farm in Tunisia lost a year's production of sea bream and sea bass after jellyfish invasions.
Perhaps the most extraordinary blooms have been those occurring in waters off Japan. There, refrigerator-sized gelatinous monsters called Nomuras, weighing 485lb (220 kg) and measuring 6.5ft (2m) in diameter, have swarmed the Japan Sea annually since 2002, clogging fishing nets, overturning trawlers and devastating coastal livelihoods. These assaults have cost the Japanese fisheries industry billions of yen in losses.
Marine ecologists are warning of worse to come, and pointing the tentacle of blame at us. Some researchers fear that human changes to the marine environment may be leading to a tipping point in which jellyfish will rule the oceans, much as they did hundreds of millions of years ago in pre-Cambrian times. In 2009, Australian marine scientist Anthony Richardson and his colleagues published a research paper entitled The jellyfish joyride, in which they warn that if we do not act to curb current blooms, we will experience runaway populations that will cause open oceanic ecosystems to flip from ones dominated by fish biodiversity to ones dominated by jellyfish.
The problem is that no one really knows what causes the blooms. Some believe that population explosions result from overfishing of their dining competitors and predators, which include more than 100 species of fish, and animals such as turtles. However, other researchers point out that overfishing also hits jellyfish by reducing their food availability.Either way, what is clear is that jellyfish are simply better prepared than other marine life for many of the ways humans are changing the ocean environment, such as warmer temperatures, salinity changes, ocean acidification and pollution. In this sense, humans might be jellyfishes’ best friend.
For instance, pollution can cause algal blooms that reduce the water's oxygen content. This hits muscular swimmers like fish hard, but jellyfish can cope far better with these conditions.
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....
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....
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.