Richard Stone: “The world’s oceans have been experiencing enormous blooms of jellyfish, apparently caused by overfishing, declining water quality, and rising sea temperatures. In recent years, populations of several jellyfish species have made inroads at the expense of their main competitor — fish — in a number of regions, including the Yellow Sea, the Gulf of Mexico, and the Black Sea. Overfishing and deteriorating coastal water quality are chief suspects in the rise of jellies. Global warming may be adding fuel to the fire by making more food available to jellyfish and opening up new habitat. Now, researchers fear, conditions are becoming so bad that some ecosystems could be approaching a tipping point in which jellyfish supplant fish.”