A significant portion of coral on the Great Barrier Reef has died, the Australian government announced as its assessment of the area entered its second phase.

The Great Barrier Reef Marine Park Authority began its follow-up investigation into the extent of coral bleaching in early October. The project aims to analyze the level of damage caused by the worst mass bleaching event on record.

An initial survey of the landmark revealed 22 percent of coral on the reef died as a result of exposure. Officials report 85 percent of this mortality occurred in the area between Cape York and Lizard Island.

Average coral reef mortality was found to be 50 percent in the Far Northern Management Area, 16 percent in the Cairns-Cooktown Management Area, and 3 percent in the Townsville-Whitsunday Management Area. No bleaching-induced deaths were found south of Mackay.

Officials note studies were completed in the Cairns-Cooktown Management Area in March, and mortality levels are likely higher than initially recorded.

Mass bleaching in the Great Barrier Reef has been linked to a sharp uptick in coral reef deaths. Australian researchers used a microscope, camera and smart tablet to examine how organisms in the area responded to the heat stress in August, marking the first time behaviors specific to bleaching were captured on film.

News of the coral deaths and subsequent investigation come as scientists refute viral claims the Great Barrier Reef has "died." While experts concede the extent of the damage is severe, they note a large portion of the area remains intact.