The secret to Tahiti's healthy coral reef
Across the world, coral reefs are dying as ocean temperatures rise. The warmer the water, the more coral bleaching occurs. But a reef discovered off Tahiti's coast appears to have remained untouched by climate change.
Great news from the South Pacific
Global warming threatens nature, both underwater as well as on land. That's why researchers were surprised when a coral reef they found in the South Pacific showed absolutely no signs of disease or dying corals. The "pristine" reef is "one of the most extensive healthy coral reefs on record," according to UNESCO. It is up to 65 meters wide (213 feet) and 3 kilometers long (1.9 miles).
The Tahiti corals are shaped like roses, some of them with a diameter of 2 meters (6.5 feet). The reef lies between 30 meters and 65 meters below the ocean's surface, an area that scientists know far less about than shallower waters. "To date, we know the surface of the moon better than the deep ocean," said UNESCO Director-General Audrey Azoulay.
Cradle of life
Coral reefs are crucial ecosystems for life in the world's oceans. They cover less than 1% of the ocean floor but are home to more than 25% of sea life, Lizzie McLeod from The Nature Conservancy told DW. Corals are made up of small creatures called polyps, and of algae, which give corals their vibrant colors.
Global heating threatens corals
Algae can start producing harmful chemicals if the water gets even a little warmer than what they're used to. The corals then expel the algae, which is their main source of food and energy, and they lose their color. In the final stages of coral bleaching, they can die completely. The IPCC has warned that with 1.5 degrees Celsius (2.7 Fahrenheit) of global heating, coral reefs could shrink by 90%.
Cooler depths ― a safe haven?
Worldwide, reefs are dying due to coral bleaching. The South Pacific around Tahiti was also hit by a wave of bleaching in 2019. Yet the newly discovered reef remained completely intact. Why? One possible explanation, scientists say, lies in the depths of the ocean where it is located ― where water temperatures are lower and corals are spared the stresses of extreme underwater heat.
Hope for deep sea corals
The discovery of the reef off Tahiti's coast could mean there are more coral reefs at great ocean depths that have so far survived the harmful impacts of rising water temperatures. It's another reminder of how little we know about the deep sea: Only 20% of the world's seabed has been mapped so far, according to UNESCO. Learning more about this reef could help protect corals everywhere.