Scientists publish interactive map
Scientists from the ARC Centre of Excellence for Coral Reef Studies at James Cook University are surveying the extent of coral bleaching at the Great Barrier Reef (GBR) by re-examining the same 83 reefs they had studied in March this year.
They discovered that many bleached corals had perished in the northern third of the GBR. The situation is made worse by disease and coral predators.
“Millions of corals in the north of the Great Barrier Reef died quickly from heat stress in March and since then, many more have died more slowly,” said Dr Greg Torda, a postdoctoral research fellow. His team recently returned from re-surveying the reefs near Lizard Island.
Footage from the scientists revealed the extent of the bleaching in March and April, which was most severe in the northern 700km section of the GBR. In the southern half, the reefs were only lightly bleached and were in good condition. (Interactive Map of the reef including photos and videos: www.coralcoe.org.au/coral-bleaching-map.)
According to Dr Torda, “Six months after the peak bleaching, the corals now have either regained their algal symbionts and survived, or they have slowly starved to death without the nutrition the algae provide to them.”
The news continues to be dire. After surveying the reefs near Lizard Island, the team discovered that the amount of live coral covering the reef fell from around 40 percent to under five percent.
“In March, we measured a lot of heavily bleached branching corals that were still alive, but we didn’t see many survivors this week,” said Dr Andrew Hoey, a senior research fellow who currently works from Lizard Island Research Station.
“On top of that, snails that eat live coral are congregating on the survivors, and the weakened corals are more prone to disease. A lot of the survivors are in poor shape,” he added.
Professor Andrew Baird led the re-surveys of the reefs in the central section, and described these reefs as being in much better shape: “There is still close to 40% coral cover at most reefs in the central Great Barrier Reef, and the corals that were moderately bleached last summer have nearly all regained their normal colour.”
All the surveys will be completed in mid-November. Nevertheless, it is already evident that the latest bleaching episode is more severe than those in 1998 and 2002.
More information: www.coralcoe.org.au