Great Barrier Reef 'cooked' by extreme temperatures
Apr 20 2018
These days, it seems like we're getting only bad news about the state of coral in the Great Barrier Reef.
"We lost 30 percent of the corals in the nine-month period between March and November 2016", Professor Terry Hughes, director of the coral-reef center at James Cook University in Australia and lead author of the new research, said in a statement. Scientists have found that a large section of corals have died and most of the coral reef has altered forever.
The team warn that if changes are not made to consider climate change it will have a huge effect on tropical reef ecosystems and, therefore, a detrimental impact on the benefits those environments provide to populations of poor nations. In particular, elaborate branching corals that provide key fish habitat are being replaced by bulky, less intricate "dome-shaped" corals, Hughes said.
It was found that of the 3,865 reefs surveyed, an alarming 30 percent had lost two-thirds or more of their coral, significantly reducing their ability to sustain full ecological functioning. Not before yet another bleaching event occurs. The south, in particular, escaped much of the bleaching in 2016 and 2017.
A staggering 29 percent of the corals in the Great Barrier Reef have perished in 2016 as a direct outcome of global warming, reveals the research, conducted by scientists from the Australian Research Council (ARC) Center of Excellence for Coral Reef Studies at the university, in collaboration with the U.S. National Oceanic and Atmospheric Administration (NOAA) in Maryland. It is a fact nearly beyond comprehension: In the summer of 2015, more than 2 billion corals lived in the Great Barrier Reef.
Bleaching occurs when the ocean's waters become too warm and expel the photosynthetic algae, called zooxanthellae, which live in a symbiotic relationship with the coral.
Partnering up with these particular algae could give corals an advantage.
The north-east coast experienced the heatwave, also known as a prolonged ocean warming event, in 2016 and according to a report by Nature Research triggered an "unprecedented loss of coral".
If warming continues apace: "Then it's game over". The composition of coral assemblages on hundreds of individual reefs changed radically within just a few months of the heatwave.
Still, 1 billion corals have survived.
Yet the remaining billion are disproportionately made up of certain species, especially in the most damaged sectors. Others were killed more slowly.
While numerous most sensitive corals died immediately from heat exposure, many others died in the months that followed after they had been bleached and then been unable to recover. "The change in the mix of species is the story".
"Unless humans get climate change under control, the increase in the frequency and intensity of marine heatwaves will destroy most of the coral reefs around the world", Eakin said. Millions rely on reefs for protection of their nations from oceanic swells, for food and for other ecosystem services.
Cobb, who witnessed a similar mass coral die-off at the Pacific island of Kiritimati in 2016, agreed that "these hardest-hit reefs will need decades to regain the level of diversity they embodied before 2016". "That is useful to be able to predict future changes and how a given level of heat exposure is likely to have impact on the corals".