The study, published on Monday in the Nature Ecology and Evolution journal, said that improving local water quality may help some reefs better withstand the bleaching impacts of climate change.

Such freshwater - carrying debris, sediments, nutrients, and other pollutants into the coastal regions - adds further stress to the Great Barrier Reef.

The beleaguered natural wonder is recovering from two back-to-back coral bleaching events in 2016 and 2017, as well as damage incurred during Cyclone Debbie in 2016 and an outbreak of predatory crown-of-thorns starfish.

The study said reefs exposed to poor water quality are more resistant to coral bleaching, but any benefit is cancelled out by their slow recovery rate and other disturbances.

So the overall impact is a negative one, said the researchers from the Australian Institute of Marine Science, who studied data on coral cover from 46 locations between 1995 and 2017.

The future of the reef will be determined by its ability to resist disturbances and recover from coral loss, they said.

Last month, plumes of polluted water from devastating floods spread to parts of the Great Barrier Reef, with photos showing one river blanketing more than 60 kilometres from the coast to the outer reef.

The Great Barrier Reef is the world's largest coral system, covering an area larger than Italy, and is one of most biodiverse ecosystems on the planet.

Australian Associated Press