Climate Change Drives Coral Bleaching, Turning Reefs White Across Caribbean and Tropics

Coral bleaching is described as a defensive response in which corals expel the symbiotic algae living in their tissues when they face drastic environmental changes such as variations in water temperature, light, or nutrients, turning corals completely white.

“MAJURO, Marshall Islands—Perched on the bow of an aluminum landing craft, Anne Cohen gazed a few yards ahead of the vessel toward a yellow robot gliding across the emerald Majuro lagoon”

Ars Technica

The main cause behind bleaching is identified as an increase in ocean temperature, described as a direct effect of climate change, with thermal rise triggering events that negatively affect coral health.

Ars Technica

The ESdiario account says the world suffered a massive loss of half of its Caribbean coral reefs in 2005 in a single year, with high temperatures centered on the Northern Antilles.

It also frames the current outlook as “the second major coral bleaching in a decade,” saying that from February 2023 to April 2024, the northern and southern hemispheres of every major ocean basin experienced significant bleaching.

Ars Technica adds that since 2023, record-breaking marine heat waves have swept through the tropics, fueling “the most severe global coral bleaching event ever recorded.”

In the Central Pacific, Ars Technica reports that Anne Cohen, a tenured scientist at the Woods Hole Oceanographic Institution in Cape Cod, uses an unmanned surface vehicle called Yellowfin to navigate to precise coordinates in the Majuro lagoon.

Cohen is quoted saying, “She’s the best dive buddy,” as the robot directs her toward a reef patch she has traveled thousands of miles to revisit.

Centre national de la recherche scientifique (CNRS)

Elsewhere, TF1 Info describes a discovery in the Tatakoto atoll off Tahiti of a coral reef recently discovered at 30 meters depth that “shows no signs of stress or disease,” and presents it as a hopeful sign for repopulating damaged areas.

UNESCO’s account says the Tatakoto atoll is located more than 1,000 kilometers from Tahiti and that expeditions supported by UNESCO, the Labex Corail, and the UPF in partnership with CRIOBE and SECOPOL and 1 OCEAN indicate that dozens of coral species thrive in the unstable lagoon.

UNESCO also reports that since 2021, six missions have been carried out at Tatakoto to determine whether exceptional resistance is due to temporary acclimation or durable genetic adaptation.

The La Relève et La Peste report describes the Tara schooner expedition, saying that on December 14 of last year, the Tara left Lorient (Brittany) and that from May 2026 it will spend seventeen months exploring the Coral Triangle.

It says the Coral Triangle concentrates a third of the world's coral reefs and nearly 600 coral species, and quotes Serge Planes, CNRS research director and co-scientific director of Tara Coral, noting, “There are no corals completely insensitive to heat.”

The same source says the expedition will conduct 1,440 dives on board Tara, with fragments of corals subjected to controlled thermal stress up to +9°C.

UNESCO warns that ocean warming triggers bleaching events in which corals expel their symbiotic microalgae, lose their color, and die if they cannot recover, and it states that the latest IPCC report warns that more than 90% of reefs could disappear by 2050.

TF1 Info adds that 70 to 90% of corals could disappear on a planet 1.5 degrees Celsius warmer than the preindustrial era, with climate scientists’ estimate for the early 2030s, and says up to 99% of corals could be threatened by 2 degrees Celsius of warming.