Marine heatwaves have wreaked “almost unprecedented” damage to ancient coral off Western Australia’s Pilbara coast, scientists say.
Preliminary results from a 5-year year study of the coastline revealed that a remote section of reef south of Barrow Island has suffered severe “bleaching and decimation,” according to the CSIRO, which is running the study with the University of Western Australia.
An extreme “bleaching event” in 2011 was known to have caused significant damage to the reef. But the study found another marine heatwave, in the summer of 2012-13, also caused trauma to the reef, including to its massive, 400-year-old porites corals.
The porites were thought to be particularly resistant to variations in climate extremes, and the cyclones which regularly hit in the area.
Modern summers give a new definition to ‘heatwave’
“To see them badly damaged, or completely dead, as a result of bleachings that happened over previous years, and likely the one in 2013, was surprising,” lead scientist Dr. Russ Babcock said.
Coral scientists expressed shock at the findings.
“It’s almost unprecedented,” said University of Western Australia professor Malcolm McCullough. “These corals were living for hundreds of years. And they died in the summer of 2012-13.”
The survival of coral depends on its symbiotic relationship with algae, which is absorbed by the coral and provides it with enzymes, sugars and its distinctive color.
“But when it gets hot, the [algae] gets damaged. And then when it receives light it’s essentially destroyed, and the coral ejects it,” McCulloch said.
Continuing temp. rise doesn’t bode well
As a result the coral becomes bleached, exposing its white skeleton. If conditions remain warm, the coral can starve to death.
McCulloch blamed the coral death on a strong La Niña phase that had produced “unusually warm waters, as well as the general increase in ocean temperatures as a result of global warming.
“Bleaching is not unusual, it’s been occurring now for about 20 years,” he said. “But by looking at the longer records the bleachings appear to be more common.”
The study is partly funded by Gorgon, which operates a nearby LNG gas project, but both Babcock and McCulloch ruled out the offshore gas fields as a possible culprit.
By Michael Safi. Source: The Guardian