University of Queensland researchers predict an increase in coral deaths this summer.

Researchers studied the Porites coral colonies or 'bommies' in the Great Barrier Reef. Porites are considered to be more resistant to environmental changes than other types of corals.

Understanding how climate change will affect the tough corals could help determine the extent of damage that the Great Barrier Reef will suffer in the future, researchers said.

"We found that there has been a significant correlation between the timing of deaths in the Porites colonies and unusually high sea-surface temperatures in the past 150 years, as well as an increased frequency of deaths in the past thirty years" said Dr Tara Clark, lead author of the study.

"Porites can live for several centuries and grow to several metres in diameter, providing important habitat for reef fishes and serving as valuable recorders of past environmental change," Clark said in a news release.

The Great Barrier Reef stretches 2,300 kilometres along the coast of Queensland and has around 2,900 reefs, according to WWF. As many as 1,500 species of fish, 30 species of mammals and 134 species of sharks and rays live in the GBR, making it one of the world's most biologically diverse regions. Recent study has suggested that the Great Barrier Reef is tougher than previously assumed.

For the present study, researchers used a modified uranium-series dating method, which was customized to calculate the timing of death of corals. Knowing the time of the coral death helped researchers find the probable causes of their death.

The team found that large number of corals died during environmental disasters such as global bleaching event of 1997/1998 and two Burdekin River floods.

"The 1997/1998 bleaching followed a strong El Niño event on top of a decline in water quality and a long-term global warming trend, which seems to have pushed the most robust corals past their tolerance limit," said Professor Jian-xin Zhao, project leader, according to a news release. "Considering that a similar El Niño event is predicted to occur this coming summer, we have grave concerns for the reef."

The study was funded by the Marine and Tropical Science Research Facility, the National Environmental Research Program and others. It is published, here