Column SFF Bestiary  A Real-Life Monster Movie Giant mindless monsters swarm the coasts, overwhelm fisheries, and defying all attempts to stop them… By Judith Tarr | Published on December 1, 2025 Photo by Maryna Seradzenka [via Unsplash] Comment 0 Share New Share Photo by Maryna Seradzenka [via Unsplash] The 2010 documentary titled Monster Jellyfish—also called Realm of Giants and Nomura’s Giant Swarm—tells a story as viscerally alarming as any monster movie. It hits all the notes: giant mindless monsters swarming the coasts of Japan, overwhelming the fisheries, defying scientists’ attempts to stop them. What’s worse, it’s not a one-off. It’s turned into an annual event. The Nomura jellyfish was first known to science around 1921. It’s one of the largest jellyfish species, with a bell growing as large as three meters (over ten feet) across. It breeds on the coast of China, at the mouth of the Yangtze River, and drifts on ocean currents until it reaches the coast of Japan. Every forty years or so, there would be a bloom of Nomura jellyfish: a massive increase in population. Then in 2002, something changed. The blooms began to occur almost annually. By 2009, Japan’s fishing industry was suffering serious losses. Fishermen were hauling in nets overloaded with 200-kilogram (440-pound) monsters, so heavy they were swamping boats. Nomura jellyfish don’t eat fish; they live on a diet of zooplankton. But blooms of jellyfish consume the zooplankton on which many fish also subsist, and cause an environmental collapse. It’s not just Nomura jellyfish. The documentary describes a series of blooms all over the world. In 2006, thirty thousand people were stung by jellyfish in the Mediterranean. In 2007, a swarm of jellyfish covering ten square miles destroyed a salmon farm, wiping out 100,000 salmon. In 2008, dozens of athletes competing in a triathlon were stung by jellyfish in the Hudson River in New York. Opinions are divided as to why jellyfish populations suddenly exploded. Climate change and warming of the oceans is a definite factor. Pollution may also contribute, along with overfishing. Somewhat paradoxically, jellyfish blooms may kill off or drive out fish by consuming all of the available zooplankton, but overfishing increases the supply of plankton on which jellyfish feed and grow. The uniquely complex life cycle of the jellyfish helps to determine the timing and extent of a bloom. The Nomura specifically has an adult life span of only a year. In that year, it grows at a rate determined by how much it is able to eat, and it does not stop until it dies. A single female Nomura produces over a billion eggs, and a male over a trillion sperm. They scatter these into the water, producing tiny fertilized larvae that attach to the sea floor. Each larva matures into a polyp that grows feeding tentacles to catch passing zooplankton. And then it gets weird. A polyp can move in a sort of walking motion, leaving behind a trail of tissue that develops into new polyps, each a clone of the original. Polyps can lie dormant for decades, until ocean conditions are just right to form saucer-like segments that break off and become tiny jellyfish. Each of these babies is a miniature version of the giant it will become in a matter of months: a stomach, reproductive organs, and eight light-detecting eyes, all protected by the bell. Eight arms hang below it, surrounded by hundreds of tentacles covered with a network of nerves that react to touch with a sting. A Nomura sting is not lethal to humans, but it can be very painful. Its purpose is to stun its prey. This fascinating animal on its own or in small numbers is not a problem, but then there are literally billions of it, it’s an ecological disaster. Masses of jellyfish choke out the oxygen in the water, drive or kill off fish, shut down beaches. The documentary shifts its focus at this point from the natural history of the jellyfish to the effects of the bloom on the humans who fish in those waters. They are, in a word, catastrophic. Various authorities have tried a number of possible ways to resolve the problem. On the grand scale of things, reversing climate change and eliminating pollution would take care of it, but realistically, that’s not happening. More localized solutions may at least reduce the size and frequency of the blooms. Direct confrontation turned out to be a terrible idea. Huge nets with metal cables shredded the jellyfish—but as they died, they released all their eggs and sperm. And now there are billions and trillions of polyps lying dormant on the floor of the Sea of Japan, waiting for conditions to be right. That’s nightmare fuel. For real. It’s all too likely that this species, which to date has bred only in China, may be about to establish a second breeding ground off the coast of Japan. If that happens, a big problem will become huge. One researcher set out to breed jellyfish in the lab, to study their life cycle in detail and try to figure out a way to short-circuit it. He did finally succeed in producing baby jellyfish, bells and tentacles and all, and he was able to determine that higher temperatures cause jellyfish to grow faster—confirming that climate change is a contributing factor to jellyfish population explosions. But as far as birth control goes, he didn’t really find anything that would work. Another possibility that seems to have had some success was the building of artificial reefs off the coast, and stocking them with file fish. File fish have thick, tough skins that are impervious to jellyfish stings, and they will happily nibble on the tentacles of a fully adult jellyfish. The principle there is to build up fish populations, especially fish that eat jellyfish, and restore the balance of the ocean. Meanwhile there are still billions of jellyfish to contend with. China deals with them by eating them. Japan has been a much harder sell. The documentary shows us a chef who has found ways to process jellyfish and developed recipes that are, according to people who have tried them, delicious. But people are just not interested. Short of a stroke of luck and a viral fad, jellyfish is not about to become a viral food sensation in Japan. Japan’s problem may only be the beginning. The more the climate changes, the more jellyfish blooms we’re likely to see, until the ocean is full of them. We have to find a way to solve the problem. We have to try to save the ocean. That’s where matters stood in 2009. I was able to find a paper that provides an update from 2009 through 2024. According to the paper, jellyfish blooms decreased significantly after 2014, but the reprieve was short-lived. By 2021, they were back. There is a glimmer of hope. The paper lists some very interesting developments in medical and environmental research. A great deal can be done with jellyfish apart from eating them, that may save human lives and help repair the planet.[end-mark] The post  A Real-Life Monster Movie appeared first on Reactor.