Coral reefs are turning white

Scientists are alarmed as coral reefs around the world are turning white due to rising ocean temperatures, which has triggered the fourth global mass coral bleaching event, according to the National Oceanic and Atmospheric Administration (NOAA).

The event threatens to be the worst ever recorded as NOAA confirmed the mass stress is in all oceans.

Around 54% of ocean waters containing coral reefs have experienced heat stress high enough to cause bleaching. The portion is increasing by 1% per week, says Derek Manzello from NOAA’s Coral Reef Watch program.

The last global bleaching event was recorded between 2014 and 2017, which saw 56.1% of the ocean’s reef corals exposed to a level of heat stress high enough to turn them white. The current event will likely surpass that, warns Manzello.

Coral reefs are important ecosystems as almost a quarter of ocean species depend on them at some point in their lives. They support fish and also protect coastal areas from storms. Reefs across the world also bring in an estimated $2.7 trillion annually in tourism.

Over the past year, mass bleaching has affected at least 53 countries, including corals in Fiji, the Florida Keys, Australia’s Great Barrier Reef (GBR), and the Indian Ocean.

• Authorities overseeing the 2,300-kilometer (approximately 1429 miles) area of the GBR recently said that more than 50% of the 1,000 individual reefs they surveyed had high or very high levels of bleaching.
• Record-breaking summer temperatures in 2023 have caused extensive coral bleaching in the Florida Keys.

Coral bleaching
Coral bleaching occurs when the water it lives in is too hot and loses the symbiotic algae it needs to survive, indicating it is starving.

Historically, bleaching events have coincided with the weather phenomenon El Nino when oceans warm up. The subsequent La Nina, which cools ocean temperatures, provides some relief to corals.

But experts now worry large-scale mass bleaching events are occurring regardless of El Nino or La Nina phases.