A relationship formed millions of years ago, around the time dinosaurs first appeared on earth, between coral and algae is under strain and it's transforming the Great Barrier Reef.
Australian researchers find corals build cloud umbrellas to help keep cool and their decline could have wider implications for climate and agricultural production.
Top End rangers filmed large patches of bleached coral from the air this year in the same area where they filmed healthy coral three years ago, and scientists are warning that more bleaching events are expected.
