Deep coral reefs at nine sites within the Great Barrier Reef are 40 percent bleached, while shallower reefs are up to 69 percent bleached due to a 2016 coral-bleaching event, according to a study published yesterday (September 4) in Nature Communications. Anywhere from 8 percent to 12 percent of shallow reefs and 6 percent of deep reefs are dead, indicating that no depth is safe from the effects of bleaching.
P. Frade et al., “Deep reefs of the Great Barrier Reef offer limited thermal refuge during mass coral bleaching,” Nat Commun, doi:10.1038/s41467-018-05741-0, 2018.