Enlarge Image Green plague. In Fiji, rarely fished reefs (top) abound with colorful corals, but seaweeds start their invasions in exploited locales (bottom) Credit: E. Hunter Hay (top); I. P. Markham (bottom) "Attack of the killer seaweed" may sound like a cheesy horror flick, but for many coral species, murderous multicellular algae have become real-life villains. A new study of reefs in the South Pacific suggests that some algae can poison coral on contact. This chemical warfare may be increasing the pressure on struggling reef communities worldwide, researchers say. Along the reefs dotting Fiji, overfishing has pitted corals against...