Various reports of huge swarms of very large jellyfish (one British report calls them “fridge-sized” and says they may weigh 450 pounds) have been cited over the last several months as evidence of climate change. Lewis Page, writing in The Register, says that “Particularly aggressive specimens are said to be capable of causing serious damage to ships, and have even managed to knacker nuclear power plants.” http://www.theregister.co.uk/2008/12/15/jellyfish_gone_wild/
Most frightening for swimmers, these slimy monsters can inflict deadly stings with their enormously long tentacles. I was hit by one in the Gulf of Mexico years back and hospitalized in Galveston. But perhaps equally problematic, they can depopulate regions of fish, interfere with shipping, clog harbors and even small seas, foul engines and have even attacked the intake valves at nuclear power plants.