Low water quality is affecting almost a quarter of the Great Barrier Reef, a new study shows.
The 10-year study carried out by the Australian Institute of Marine Science found 22 per cent of the Great Barrier Reef – almost 650 reefs – did not meet water quality guidelines.
The study found reefs with poorer water quality suffered a loss in coral biodiversity and an increase in seaweed cover.
“Seaweed is not bad, it’s a naturally occurring part of a coral reef,” AIMS coral reef ecologist Dr Katharina Fabricius told AAP.
“However, once it occurs in too great abundance it occupies space that is then not available for coral to recolonise after disturbances such as bleaching events of crown-of-thorns starfish outbreaks.”
The study also identified the water quality threshold, a measure of nutrients in water, which determine whether a reef will be healthy or unhealthy.
Dr Fabricius said the thresholds had already been used by the Great Barrier Reef Marine Park Authority to determine water quality guidelines.
The guidelines are utilised in discussions with governments and farmers along the north eastern coast of Australia about restricting the run off of nutrients from their properties.
“We don’t want to stop farming, what everyone wants is to keep top soil on the farm where it is doing a good thing,” she said.
Dr Fabricius said the biodiversity of affected reefs would improve over time if nutrient levels were reduced.