The Con Dao National Park Management Board said Friday that the reef damage occurred a few days ago 30-40 meters from shore.
Temperatures at the bottom of the water have hovered around a hot 32 degrees Celsius in recent times while the ideal range for corals is 24-30 degrees.
The high temperature causes the corals to expel the algae living in their tissues, thus preventing photosynthesis and leading to their death.
The El Niño-Southern Oscillation is a recurring climate pattern caused by changes in water temperature in the central and eastern tropical Pacific Ocean.
Son said some coral species have a significant recovery potential when water temperatures drop. However, if the temperatures continue to stay high, a large number of corals will die.
Bleached coral in Con Dao National Park, May 2024. Video by Minh Bang
Currently, the Con Dao National Park Management Board is collaborating with the Nha Trang Institute of Oceanography in Nha Trang City to conduct more detailed surveys and assessments of this situation.
Con Dao Archipelago off the coast of Ba Ria - Vung Tau Province comprises 16 large and small islands spread over an area of 76 square kilometers.
The main island is one of the top tourist destinations in Vietnam.
Con Dao National Park spreads over 19,998 ha with forest and forest lands accounting for 5,998 ha and a biodiversity marine protected area for 14,000 ha with a buffer area of 20,500 ha.
Corals thrive in the park, with 360 species spread over an area of 1,500 hectares.
Coral death phenomena occur frequently on Con Dao, with the most severe instances being in 1998, 2010 and 2016 due to El Nino.
According to research by non-profit Global Coral Reef Alliance, extreme temperatures worldwide are the main cause of coral bleaching, a process that turns them white and strips them of their vibrant colors.
Scientists have found 2023 to be the worst year ever for coral bleaching in the northern hemisphere.
They expect the southern hemisphere to experience its worst year in 2024.
Nearly two-thirds of the world's coral reefs have been subjected to heat stress bad enough to trigger bleaching over the past year, the U.S. National Oceanic and Atmospheric Administration said in May.