Great Barrier Reef Threatened

The above image, taken on Feb. 9, of Princess Charlotte Bay in far North Queensland shows the sediment plumes (brown and green) against the blues of the "normal" reef waters.

Remotely sensed images like this one taken from Feb. 9 through Feb. 13 provide visual evidence that sediment plumes in the Great Barrier Reef system flow to the outer reef. The snapshots challenge conventional assumptions, which have held that the churned up water gets captured by longshore currents and travels just six to nine miles (10 to 15 kilometers) offshore, never reaching the outer reefs.

Not only did the images show the plumes moving at a swift pace, the water reached as far as 80 miles (130 kilometers), to the outer reef. Managers of the reef system have long examined the effects of pesticides, herbicides and fertilizers that hitch rides within the sediment loads.

Heavy rainfalls in northern Queensland resulted in flood waters that carried atypically large sediment loads from creeks and rivers. Such floods haven't occurred for some time, and the accumulated material in the rivers coupled with increased sediment runoff from the land is causing a significant transport of material to all areas of the reefs.

"A re-think is needed now that we know where flood plumes go," said Arnold Dekker of Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO). "And what this means as organic micro-pollutants may be traveling to parts of the reef scientists hadn't thought to look before."

--LiveScience Staff

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Credit: CSIRO/GeoScience Australia