After record-high temperatures for the last four months of 2021, the Great Barrier Reef is at risk of another mass bleaching event. Experts are shocked and concerned by the unprecedented levels of heat stress on the corals.

From September through December 14, 2021, National Oceanic and Atmospheric Administration (NOAA) noted more heat stress over the corals than usual. During these months, the minimum temperatures in an area spanning over 80% of the reef system were higher than any maximum temperatures ever recorded.

“There’s never been heat stress like that in our records,” said William Skirving, senior scientist and oceanographer with NOAA’s Coral Reef Watch. “It’s completely out of character and speaks to the fact that the minimum temperatures were higher than the previous maximums. This is almost certainly a climate change signal. Being a scientist in this field in this day and age is sometimes a bit nightmarish. Sometimes I wish I knew a little bit less.”

By mid-December, ocean temperatures were 0.5°C higher than water temperatures immediately preceding previous bleaching events, which could be a warning of what’s to come for the reef this year. Researchers are monitoring the area closely, and not all is doomed yet. Extended cloud cover, rain, and wind over the next several weeks could lower temperatures, and mass bleaching may still be avoided.

Scientists anticipate coral bleaching events to become more frequent in a warming world, but the Great Barrier Reef has already experienced multiple mass bleaching events in 1998, 2002, 2016, 2017 and 2020.

During a mass bleaching, temperatures cause algae, which provide food and vibrant color to coral, leave, and the coral reefs turn white. While they can recover from these events, the corals come back more vulnerable to diseases and with lower reproduction numbers.

Read the full article about barrier reef bleaching by Paige Bennett at EcoWatch.