Australia’s Great Barrier Reef is experiencing one of its worst bleaching events since monitoring began nearly four decades ago, authorities say, with much of the famed reef showing signs of damage as warming ocean temperatures blight reefs worldwide. Bleaching occurs when heat-stressed coral turn white after expelling symbiotic algae that provide food and color. It’s a result of abnormal ocean temperatures in the past year that scientists worry could represent a major change to Earth systems. In the Great Barrier Reef marine park, 73 percent of the reefs surveyed have prevalent bleaching - which means that more than 10 percent of the coral cover is bleached, the Great Barrier Reef Marine Park Authority, which manages the area, said Wednesday. Very high and extreme bleaching was observed across nearly 40 percent of the reef system. “Climate change is the greatest threat to the Great Barrier Reef, and coral reefs globally,” said Roger Beeden, the authority’s chief scientist. “The Great Barrier Reef is an incredible ecosystem, and while it has shown its resilience time and time again, this summer has been particularly challenging.” The dire update on Earth’s largest reef system comes just days after scientists with the U.S.-based National Oceanic and Atmospheric Administration and the International Coral Reef Initiative said anomalous ocean temperatures are afflicting reefs worldwide. According to NOAA scientists, the world is experiencing its fourth global bleaching event, and the second in the last decade. At least 53 countries and local regions have experienced mass bleaching across the Atlantic, Pacific and Indian oceans, they said. Ocean temperatures began building in the Great Barrier Reef area in late December and continued to rise throughout the Southern Hemisphere summer, causing “the highest levels of thermal stress on record,” the marine park authority said. The most intense and prolonged heat stress occurred... |