SHINICHI Ue, a professor at Japan’s Hiroshima University, warned that “the world’s seas will be in big trouble”, if the international community “fails to get serious about countermeasures against jellyfish massive outbreaks.”
A study by Ue found the jellyfish, especially Nomura jellyfish, are born in northern parts of the East China Sea. China’s coastal areas have been significantly developed, and its seashores are rapidly being overrun by concrete embankments. These embankments provide ideal surfaces for polyps – baby jellyfish – to stick to and grow. Polyps- those clone sacks that churn out baby jellyfish are “key to their ability to bloom in such incredibly rapid fashion and shocking numbers. Fast-developing Chinese coastal areas are also pouring huge amounts of sewage and agricultural wastewater into the sea. This contains nitrogen and phosphorus, which boost the populations of plankton on which jellyfish thrive.
Jellyfish feed on zooplankton drifting in the seas. A particularly large Nomura’s jellyfish takes in enough seawater each day to fill a swimming pool, gobbling up any plankton it catches in the process.
Due to overfishing and pollution, jellyfish have few predators such as tuna, salmon, swordfish, sea turtles and albatross – animals that are increasingly scarce. Some jellyfish eat 10 times their own body weight every day. They feed on eggs of other fish, and also eat up the food that other species need to survive, which collapses fish populations. They can live in polluted waters like “dead zones” created by what scientists call “eutrophication,” where oxygen depletion of the water body happens, where other fish cannot live. They need very little oxygen to survive. So as other animals dwindle, jellyfish colonies expand. Even global warming may be good for jellyfish. In fact, some jellyfish have more babies in warmer water.
