The news is almost unrelentingly grim for shallow water coral reefs. Bleached by rising temperatures, harmed by overfishing and more frequent natural disasters and with changing ocean chemistry inhibiting their recoveries, the ocean's richest and most beautiful ecosystems may vanish in our lifetime. So marine biologists are as astonished as they are delighted to discover an exception, a coral reef experiencing a growth spurt.
One Tree Island sits near the southern end of the Great Barrier Reef (GBR). The coral that fringes it is part of a collection of reefs cut off from the bulk of the reef by the Capricorn Channel. Since 1976 a research station has been located there, making this otherwise apparently ordinary reef the subject of an unusual amount of research.
“A devastating cyclone hit the One Tree Island reef in 2009, and no metabolic recovery was detected even five years after. In 2014, calcification had declined at One Tree Island by 75 percent, and we expected this trend to continue due to ocean acidification inhibiting coral recovery,” said Southern Cross University PhD student Kay Davis in a statement. “However, we found that the coral ecosystem has completely recovered from this cyclone event after eight years.”
In three years the rate of new coral formation – measured through chemical analysis of the water – jumped 400 percent, Davis reports in Frontiers in Marine Science. It is now slightly higher than 50 years ago, before things started to go wrong for the world's largest system of coral reefs. A 70 percent increase in coral area confirmed the finding.
One Tree Island Reef's southern location means corals start at the cooler end of their comfort range and tourists and fishing are banned. It's also far enough offshore to avoid the worst effects of runoff, but that still doesn't explain why the growth is so fast.
Davis told IFLScience she is not aware of any similar positive findings elsewhere using the same techniques, but pointed out “The field of water chemistry for reefs is still quite small.” She added the GBR's southern end suffered far less damage from recent bleaching events than the north, but has not yet had a chance to see if other reefs are experiencing the same surge in coral production, leaving the cause a mystery.
Meanwhile, Davis has another research site at Lizard Island near the GBR's opposite end. Despite having some of the same protections as One Tree Island, Lizard Island is, in Davis' words, in “total ecosystem collapse”, with coral formation almost halving, and algae taking over.
Without understanding the cause we can't predict if One Tree Island will continue to thrive. If it does, one can only imagine how precious it will become, and how great the pressure will be to allow tourism, as others disappear.