In a world where 93 percent of the Great Barrier Reef has been destroyed, from Hawaii to the Indian Ocean, about 12,000 square kilometers of coral reefs are predicted to be destroyed by the end of the year. The problem of coral reef bleaching has become too serious to ignore.
Now, for the first time, scientists have photographed the process of coral reef bleaching, which is more rapid and severe than previously predicted.
For the uninitiated, the causes of coral reef bleaching are often attributed to environmental changes, such as rising temperatures and increased pollution.
Coral reefs themselves don't grow the "hats" that make them colorful—thanks to the algae that live within the coral tissue. They provide reefs with an abundance of nutrients in exchange for a safe place to live and reproduce.
This mutually beneficial relationship between reefs and algae -- also called a symbiotic relationship -- is a perfect fit for both parties. But when conditions get worse, the reefs will brutally drive off the algae to protect themselves, and in the process, the reefs will turn white.
Reefs will die if living conditions are not restored quickly enough to allow new algae to take root.
What's really interesting is that coral reefs are always pretty quick and rampant when it comes to expelling their symbiotic inhabitants," said Brett Lewis of the Queensland University of Technology in Australia. Lewis' team has been watching reef species during bleaching, especially rock coral.
After controlling for the environmental variables of the stony corals and symbiotic algae, the researchers were able to observe and record their responses to temperature increases.
For the first twelve hours, the team raised the water temperature from 26 degrees Celsius to 32 degrees Celsius (78-89 degrees Fahrenheit) and kept the temperature there for the next eight days. At this water temperature, the reef loses its color within a few hours.
"The stony corals start to drive off the symbiotic algae that live on them within two hours of rising water temperatures," says Lewis.
"Our stony corals use a pulsed expansion to expel the symbiotic algae - the reef first expands itself to 340 times its original size, then opens its mouth and ejects the symbiotic algae through rapid contraction and jetting. Experiments The reef repeats this process from day four to day eight," added Luke Northduft, another researcher on the team.
Even more troubling, the researchers say they chose stony coral because it is the best-living and hardiest reef species on the Great Barrier Reef.
Mature stony corals are approximately 20 cm in diameter and 7 cm in height (7.8 and 2.7 inches, respectively), a unique mushroom-shaped coral that feeds on a large amount of sugar produced by symbiotic algae. And these algae also use their fearsome tentacles to capture plankton from the surrounding waters.
Symbiodinium has a colorful appearance, from dark brown to soft velvety green, bright and stunning iridescent, yellow, pink, purple and red, all of which can be found in Symbiodinium. No kidding, at first glance they look like they've stepped out of an underwater fairy tale world.
Although stony corals are listed as endangered on the IUCN Red List of Threatened Species, previous research has shown that stony corals are well-adapted to the challenges of thermal change and have exceptional resilience. Now Lewis and his team think this may be because stony corals have an unimaginably fast response time.
"Our observations suggest that the rapid recovery of stony corals may be due to their ability to rapidly expel symbionts during temperature changes, thereby greatly increasing their odds of surviving abnormally warm ocean temperatures," he said.
Aside from a deeper understanding of the behavior of coral reefs, the researchers had no other good news, and the status quo remains bleak.
What we now know is that stony corals, one of many reefs on the Great Barrier Reef, have survived relatively well in the side effects of global warming. But its survivability is strong because it knows how to abandon the car and keep it handsome. It realizes faster than other species that it needs to sacrifice the nutrients it needs to survive, which is a rather terrifying concept.
We can now only hope for more and more in-depth scientific research. It is hoped that scientific research will give us a better understanding of coral reefs and the plight they face, and a better chance for the government to formulate relevant policies, so as to give the last 7% of coral reefs a silver lining and prevent them from being bleached again.
Lewis' team's research has been published in Coral Reef.