The Amazon River is known far and wide for its vast array of wildlife ranging from pink dolphins to flesh-eating piranhas and has now revealed a new treasure trove - a massive coral reef that stretches for some 600 miles, scientists say.

Scientists unveiled the first smoking-gun evidence Wednesday that growing ocean acidity caused by global warming is already stifling growth of vital coral reefs.

Corals worldwide are at risk from a major episode of bleaching which turns reefs white, scientists have confirmed.