Gelatinous swimmer swarms can be so great they destroy all the other fauna, they've even caused nuclear power plants to shut down by clogging pipes. This would make jellyfish natural terrorists and threats to homeland security wherever they invade. No continent is immune.
Sea nettle, an abundant Arctic jellyfish with 20' tentacles. Photo courtesy NSF and Kevin Raskoff.
Here's some of what the NSF report has to say about the jellyfish swarms. "Jellyfish swarms have also damaged fisheries, fish farms, seabed mining operations, desalination plants and large ships. And proving that jellyfish can be political animals, knots of jellyfish have done the work of anti-nuclear activists: they have disabled nuclear power plants by clogging intake pipes. In short, since the 1980s, worldwide jellyfish blooms have caused hundreds of millions--or perhaps even billions--of dollars in losses."
Much of the recent research into these jellyfish swarms is heavily dependent on high tech submersibles, and computer modelling that can quantify the complex factors affecting jellyfish blooms and busts.