50% Of The Great Barrier Reef Is Dead Or Dying
There is unprecedented dying of Great Barrier Reef in the past years, with 50% mortality of the reef due to coral bleaching. Recent work on the Great Barrier Reef (GBR) indicates widespread disease, pollution, and bleaching of coral has led to more than half of the coral dead or dying to date.
Corals live in symbiosis with microalgae, called zooxanthellae, which provide the coral with nutrients and their incredible colors. When the surrounding waters become too warm, diseased, or polluted the zooxanthellae leave the corals. This leaves the corals bleached white and with little to no nutrients, hence the term coral bleaching. This does not kill the coral but leaves it in a weakened and stressed state. Eventually bleached corals can bring in new zooxanthellae but the environmental conditions have to swing back into balance before that is likely to happen.
Eventually, without the symbiotic relationship of the zooxanthellae, corals are overwhelmed by brown-green algae and other organisms and will die. Thankfully the southern hemisphere winter is coming to an end, bringing cooler temperatures that will stave off coral bleaching at least for a few months.
This is the worst coral bleaching episode in Australias history, with reports of coral dying in places that we thought would be protected from rising temperatures. Ove Hoegh-Guldberg, University of Queensland Global Change Institute Director Professor, said in a statement to the University of Queensland press.
http://www.forbes.com/sites/trevornace/2016/04/24/50-great-barrier-reef-dead-dying/#14545e8b1aea