The study was published Monday in the online edition of the journal Proceedings of the U.S. National Academy of Sciences (PNAS).

　　The researchers investigated the interactions between eight different species of seaweed and three species of coral growing in the waters nearby the Fiji Islands, and identified a class of anti-coral organic compounds known as terpenes.

　　These chemicals, found on the surfaces of several species of seaweed, can kill the coral by suppressing its photosynthesis.

　　The finding suggests that the living space competition with seaweeds could be a factor of the coral's worldwide decline.

　　Plant-eating fish normally controls seaweed growth on coral reefs, but the populations of these consumers are declining by the overfishing, which eventually resulted in the seaweed's dominant position, according to the researchers.

　　Despite overfishing, pollution and warming oceans are also the contributors to coral's worldwide decline, said Jennifer Smith, a marine ecologist at the University of California, San Diego.