"Severe bleaching" refers to a situation where something, such as coral reefs or hair, loses its natural color and becomes very pale or white. Full definition
The median time between pairs of severe bleaching events has also decreased, the researchers found — it's now just under six years, versus 25 to 30 years in the early 1980s. (sciencenews.org)
Australia's Great Barrier Reef is undergoing the most severe bleaching event in its history, as corals along the reef expel the symbiotic algae that provide them both with their rich colours and food. (scientificamerican.com)