An outbreak of coral bleaching has been reported over the summer in Gang Gurak Barlu National Park on the Cobourg Peninsula, 60km northeast of Darwin, homeland of several clans of the Iwaidja-speaking Aboriginal people of Western Arnhem Land.
As no formal monitoring or assessment program is in place for these reefs, it’s impossible to gauge the full severity and extent of the bleaching. However, this video from Black Point on the Cobourg Peninsula contrasts the healthy reef in 2015 and the bleached reef in 2018.
The Northern Territory has unique marine ecosystems which are largely untouched and sit in waters receiving flow from untamed rivers. There are extensive coral reefs with abundant breeding turtle populations, saltwater crocodiles and sharks.
In January this year, the water temperature between the Northern Territory and Papua New Guinea reached what the National Oceanic and Atmospheric Administration (NOAA) calls Alert Level 2 – its highest alert for the risk of bleaching and subsequent coral death.
This is an indication of the duration and intensity of a warming event, measured in “degree heating weeks” – the number of degrees above the average summer maximum temperature, multiplied by the number of weeks. Alert Level 2 indicates at least eight degree heating weeks.
This is not the first time coral bleaching has been seen in the NT. Severe bleaching was recorded in seas off Arnhem Land during the global bleaching event in 2015-16.
Increases in sea surface temperature cause mass bleaching events. The bleached corals have lost most of the single-celled algae, called zooxanthellae, that live and photosynthesise inside the coral cells and provide the corals with most of their energy.
The Great Barrier Reef also suffered severe bleaching in 2016. This resulted in 67% mortality in its northern sections, dwarfing the effects of previous bleaching events in 1998 and 2002.
Originally Published by The Conversation, continue reading here.