In a world where 93 percent of the Great Barri×"er Reef has been destroyed, from Hawaii to th∞☆e Indian Ocean, about 12,000 square kilometers <•&♦of coral reefs are predicted to be destroyed b≈™y the end of the year. The pr¥↕→≈oblem of coral reef bleachin↔ε g has become too seriousα∑$ to ignore.
Now, for the first time, sci<δentists have photographed ÷>the process of coral reef ∏σ↑bleaching, which is more rapid and se≤↓®vere than previously predicted.
For the uninitiated, the ♠λ✔causes of coral reef bleaching↕→ε± are often attributed to environme↕≠εntal changes, such as rising ∑÷temperatures and increased∏ pollution.
Coral reefs themselves don't§↓♠→ grow the "hats" that make them colorf♣®Ωul—thanks to the algae that li§₽×ve within the coral tissue. They ε<§provide reefs with an abπ>undance of nutrients in exchange↑₩ for a safe place to live and reproduce.
This mutually beneficial relationship between re&÷≠efs and algae -- also called a symbiot↕¶ic relationship -- is a perfect fi≠∑→₽t for both parties. But when conditions get wo¶<ε₩rse, the reefs will brutally γβdrive off the algae to protect themselves, and in★ Ω♣ the process, the reefs will turn wh★↕ite.
Reefs will die if living conditions are 󱶮not restored quickly enough ↔∑to allow new algae to take root.
What's really interesting i÷☆s that coral reefs are always pretty q∑↑§uick and rampant when it comδ↑es to expelling their sym♣↑☆☆biotic inhabitants," said Bγ≈ rett Lewis of the Queensl and University of Technology in Austr¶×÷alia. Lewis' team has been watching re♠¥♠∑ef species during bleaching™≈•, especially rock coral.
After controlling for the e¶↑ nvironmental variables of the stony coralsπ↓ and symbiotic algae, the researchers wα₽ere able to observe and reco±★↕rd their responses to temperature inc•α&reases.
For the first twelve hours, the team rais♥Ω÷ed the water temperature δ>&from 26 degrees Celsiu>←₹φs to 32 degrees Celsπ®∞ius (78-89 degrees Fahrenhe↓ σ↑it) and kept the temperature ther∏&∞£e for the next eight days. At this water tempera↑ε¥ture, the reef loses its color wi×↓thin a few hours.
"The stony corals st₹art 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 Ω÷&∞expansion to expel the symbiotic a↔δlgae - the reef first ¥σ®expands itself to 340 times its origi×δ±nal size, then opens its mout¶&h and ejects the symbiotic algae t×$÷hrough rapid contraction and jetting. Experiments↔α★ The reef repeats this process•₽↓ from day four to day eight," added Luke Nor↑≥thduft, another researcher on the team.
Even more troubling, the researchers say they∞© chose stony coral because it is the§✔Ω best-living and hardiest ↕÷≥★reef species on the G λ→"reat Barrier Reef.
Mature stony corals are approxima≤₩©tely 20 cm in diameter and 7 cm in height (7§α←≠.8 and 2.7 inches, respe©£ctively), a unique mushroom-shaped coral tσ∑σhat feeds on a large amount of suga∞★β✘r produced by symbiotic algae. And these a≤₽δ"lgae also use their fearsome tentacles to c®→<apture plankton from the surroundi"'ng waters.
Symbiodinium has a colorful appeara $nce, from dark brown to soft↕&↑♣ velvety green, brigh©εt and stunning iridescent, yellow, pink, purple↕ " and red, all of which can be found in SymbioΩ₽dinium. No kidding, at first g♥γγlance they look like t≈γקhey've stepped out of an u₽∏♠nderwater fairy tale world.
Although stony corals are listed as endange&∑≥¥red on the IUCN Red List of Threatened Spπφ&ecies, previous research ha ¥πs shown that stony corals are well-adapted to thσ♠∞e challenges of thermal c≈↑↑hange and have exceptional resilienc→®∑e. Now Lewis and his te"₽λam think this may be b>ecause stony corals have an unimaginably fast re≠<✘sponse time.
"Our observations suggest that the rapid ★™€recovery of stony corals m∏÷ay be due to their abα§≤≥ility to rapidly expel sym↔γbionts during temperature chang→ es, thereby greatly increasing their odds of s>&urviving abnormally warm ocean tempera≥<πβtures," he said.
Aside from a deeper underst÷♣γanding of the behavior of★λγβ coral reefs, the researchers had no β§δ≤other good news, and the stat♠±us quo remains bleak.
What we now know is that stony corals, one of ma₽>ny reefs on the Great Barrier Reef, have survived≠γ≈ relatively well in the side effects of global ₹÷πwarming. But its survivability i×♦s strong because it knows≥÷ how to abandon the car and keep it handsome. Iλ≤≈t realizes faster than other speπ↔cies that it needs to sacrifi∞↕ce the nutrients it needs to survive, which is$& a rather terrifying concept.
We can now only hope for more a↕♠©nd more in-depth scientific research. It is ho↔±"×ped that scientific research will give us a φ₹₹σbetter understanding of coral reefs and the plig'✔ht they face, and a better chance for §↔✔γthe government to formulate relevantα✔ policies, so as to give the last 7λσ% of coral reefs a silver lining andφ±→∑ prevent them from being bleach→✔€ed again.
Lewis' team's research has been publi∑÷¥shed in Coral Reef.