30 percent of the coral died during mass bleaching in 2016
A recent study, published recently in the online journal Nature, reveals that massive corals have died in the northern Great Barrier Reef after the extensive heat wave of 2016.
"When corals get bleached during a heat wave, they can either survive and slowly regain their colour when the temperature drops, or they can die off. In average 30 percent of the coral in the nine-month period between March and November 2016 for the entire Great Barrier Reef died and have been lost," said Prof. Terry Hughes, director of the ARC Center of Excellence for Coral Reef Studies (Coral CoE).
The scientists mapped the geographic pattern of heat exposure using satellites and documented the survival of the corals on the 2,300 km long Great Barrier Reef after the extreme heat wave of 2016.
The extent of coral extinctions was closely related to the extent of bleaching and heat stress, with the northern third of the Great Barrier Reef being hit hardest. The study found that 29 percent of the 3,863 reefs that make up the world's largest reef system lost two-thirds or more of their coral. The ability of these reefs to maintain their full ecological functioning changed.
"Coral dying has led to radical changes in the composition of coral species on hundreds of individual reefs, transforming multiple reef communities into degraded systems with only a few resistant species remaining," said co-author Professor Andrew Baird of Coral CoE.
"As part of a global heat and coral bleaching operation in 2014-2017, the Great Barrier Reef experienced another significant heat stress and bleaching in 2017, this time in the central region of the reef," said co-author Dr. Mark Eakin of U.S. Pat. National Oceanic and Atmospheric Administration (NOAA).
"We are now at a point where we have lost almost half of the corals in shallow water habitats in the northern two-thirds of the Great Barrier Reef," adds Prof. Sean Connolly of Coral CoE.
But, according to the researchers, there are still a billion corals alive, which on average are more resistant than dead ones. Now it is time to help the surviving corals to recover.
"The Great Barrier Reef is certainly threatened by climate change, but it is not doomed to deal with greenhouse gas emissions very quickly, our study shows that coral reefs are already radically changing in response to unprecedented heat waves," says Prof. Hughes ,
The researchers warn that the non-containment of climate change, which causes global temperatures well above 2 ° C, will radically change tropical reef ecosystems.
Link to the study: https://www.nature.com/articles/s41586-018-0041-2.