The photo shows a giant Echizen jellyfish, which has a body almost 5 feet across, floating near the coast of northern Japan. The combination of overfishing, high levels of pollution, higher sallinity and warmer waters due to global warming can lead to what researchers call a “jellyfish stable state” in which jellyfish rule the oceans. Jellyfish numbers are increasing everywhere: in Southeast Asia, the Black Sea, the Gulf of Mexico, the North Sea, Mediterranean. At the same time, populations of jellyfish predators such as tuna and turtles are diminishing. Jellyfish are normally kept in check by fish, which eat small jellyfish and compete for jellyfish food such as zooplankton. These huge creatures – a jellyfish called Nomura, which is the biggest jellyfish in the world, can weigh 200 kilograms (440 pounds) and is 2 meters (6.5 feet) in diameter – can burst through fishing nets, as well as destroy local fisheries with their taste for fish eggs and larvae. Nitrogen and phosphorous in run-off cause red phytoplankton blooms, which create low-oxygen dead zones where jellyfish survive, but fish can’t. In contact with human skin, jellyfish might provoke a powerful allergic reaction or even death, if it is a poisonous specimen like box jellyfish, the most venomous marine creature, which contains enough poison to kill three adult human beings.