Floodwaters pose major threat to reef

FLOODWATERS washed out to sea could spell disaster for the Great Barrier Reef.

Aerial shots have shown sediment laden waters from the Burdekin River extending out to Old Reef about 60km offshore.

Senior research scientist Jane Waterhouse of TropWATER Catchment to Reef Research Group said the unprecedented rain event presented a multi-pronged threat to the reef.

She said it could lead to bleaching but there were a number of threats in the immediate term.

"The short terms effects we will see is a drop in light. (Then) once that dirty water settles you'll get algae growing," she said.

"Sometimes around Mission Beach and Tully it's like a pea soup.

"Having this much nutrient in the water you get a lot of algae growing ... some of that is favoured by the crown of thorn (starfish) larvae."

Ms Waterhouse said dirty water was detrimental to the seagrass beds in Cleveland Bay.

In the past fortnight about 14 million megalitres of water was discharged from the Burdekin River, the equivalent of 5.6 million Olympic sized swimming pools.

It is the largest discharge from the river in eight years.

Ms Waterhouse said there was concern high volume of floodwater could impact the reef's recovery.

"When the coral are already stressed and we have a major event like this, the chances of recovery are reduced a lot more," she said.

Ms Waterhouse said the reach of this plume was unique as a result of the calm weather following the monsoonal downpour.

"It's devastating how far off (the run out) has gone," she said.

"Quite often when we have these flood event we typically have winds.

"At the moment because we've got quite calm conditions, the river plume is tracking straight out to sea."

TropWATER staff are continuing to monitor the river plumes.