Great Barrier Reef Health Information
Update #2 – 11 April 2016:
2 weeks ago we spoke to our Marine Biology experts for some up to date information about what coral bleaching is and to what extent it was affecting our region.
Today we catch up with the Quicksilver Group’s Environmental & Compliance Manager, Dougie Baird, to get an update on current conditions and have a chat with some guests to find out about their reef experiences.
Update #1 – 31 March 2016:
The Great Barrier Reef is a massive, dynamic living natural wonder spanning 344,400 sq km. In light of the recent media coverage about coral bleaching, the Quicksilver Group have put together some of the facts. Two of the Quicksilver Group’s senior environment and marine biologists give us a better understanding of what coral bleaching is and what the impacts are.
Commonly asked questions about Coral Bleaching:
Coral bleaching is caused when coral under stress voluntarily expel the microscopic marine algae, called ‘Zooxanthellae’, from their cells. Through photosynthesis these algae give corals most of the energy they need to grow, reproduce and provide the colour to the coral. As a coral gets more stressed more and more Zooxanthellae are ejected from the transparent tissue of the coral, and more of the corals white skeleton is revealed. The coral is still alive, but is in a distressed state.
Bleaching can be caused by a number of things: prolonged elevated ocean temperatures, sudden temperature drops (as seen in the southern part of the reef in winter occasionally), extreme amounts of freshwater (usually caused by tropical storms) and sedimentation caused by run off. What some areas of the reef are currently experiencing is above average ocean temperatures caused by a severe El Nino event, similar to what was experienced in 1998.
The Great Barrier Reef consists of 4 general sections: Far Northern Section, Cairns Section, Central Section and the Mackay-Capricorn Section. The area under the most stress from the current bleaching event that is being widely report in the news media, is the Far Northern Section that runs from Lizard Island up to the tip of Cape York. Lizard Island is approx. 200kms north of Port Douglas and 250kms north of Cairns.
The ‘Cairns Section’ which runs from Cooktown, past Port Douglas and down past Cairns, is not experiencing the extreme bleaching event seen in the Far Northern section.
All corals can be affected to varying degrees, but Staghorns and corals in shallow water are the most at risk. Soft corals are the most resilient, but if exposed to high water temperature for prolonged periods of time they will experience paling and eventually bleaching (1 degree Celsius above normal summer max temperature for 4 weeks is normally the trigger).
It can be, but not always. Importantly, coral bleaching does not mean a death sentence. As corals get most of their energy requirements from the zooxanthellae, without them the corals starve, but if the causative stress is short lived, the plant cells will be reabsorbed and the corals colour rebounds quickly. These corals may however experience reduced growth and reproductive capability for that year, and are more vulnerable to disease. The more prolonged the stress event, the more chance of mortality.
Yes, the Great Barrier Reef system is over 18 million years old and has rebounded from various geological events like Ice Ages, low sea water levels, and warmer water over its enormous life span. In the current bleaching event, some corals will recover once ocean temperatures drop below 29.5 degrees Celsius and corals that have died can be recolonised by coral larvae during the next spawning event. In some cases recovered areas may be recolonised by hardier corals and be more robust for future events.
It depends on the severity and length of the bleaching event, as well as the type of coral involved. It could be weeks, months or even years.
In the short term not much. In the longer term, fish which normally hide in coral colonies may be more visible to predators and therefore more vulnerable, and fish that normally eat coral polyps will find their food source is reduced.
Currently the reefs off Port Douglas and Cairns have proven to be very robust in the face of the current bleaching event. When the sea temperature decreases as is now trending as we move into April, affected corals will start to recover with minimal mortality. If the water temperatures remain high, then mortality in the staghorn and other more susceptible corals will become visible.
Recent photos taken at reef sites
Agincourt Reef – Poseidon
Agincourt Reef – Quicksilver