Mortality on the Great Barrier Reef
Photo: ARC Centre of Excellence in Coral Reef Studies
After the most widespread and severe coral bleaching event on the Great Barrier Reef, scientists are continuing to watch the health of the reefs closely. In October 2016, 6 months after the high temperature event, scientists have returned to conduct surveys and measure coral survivorship and mortality. They have found that many of the corals that bleached have now died on the northern areas of the Great Barrier Reef and this mortality is compounded by predation from coral-eating invertebrates like snails. Scientists are concerned that even though some corals are surviving, the thermal stress may have weakened their immune systems, making them susceptible to disease. On coral reefs near Lizard Island, for example, the live coral cover has fallen from approximately 40% to under 5%. Full surveys of the Great Barrier Reef will be completed in mid-November, however, preliminary data shows that the 2015/2016 bleaching event is more severe that those in 2002 and 1998.
Fortunately, there are many corals that have since regained their algal symbionts and recovered, especially in the southern portions of the Great Barrier Reef. The ARC Centre of Excellence in Coral Reef Studies has released an interactive map with photos and videos showing the extent of the bleaching event. You can view the map here: https://www.coralcoe.org.au/coral-bleaching-map.