Algae may have launched coral reefs by hijacking coral cells, genetic experiments suggest

The reefs scattered throughout the tropics arose only after algae took up full-time residence in coral cells, supplying corals with abundant food and enabling them to build extensive shallow-water communities.

But with warming oceans, algae are often abandoning coral—causing what's known as bleaching—and turning reefs that were once teeming with life into ghost towns. ...