Great Barrier Reef
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Great Barrier Reef

April 7, 2007

In late February 2007, NASA satellite images revealed that even the outer portions of the Australia's Great Barrier Reef can be bathed in land-based pollution carried far offshore by plumes of river water. Conventional thinking was that river plumes affected only the lagoon and the inner portions of the reef. But images from the MODIS on NASA's Terra satellite verify a new theory that not even the outer reefs are spared the impact of land-based pollution, which includes excess sediment, fertilizers, and pesticides.

This image from February 9, 2007, shows plumes of sediment flowing into Princess Charlotte Bay, which is about halfway down the east coast of Queensland's Cape York Peninsula. After heavy rains fell in late January and early February, several rivers were emptying muddy water into the bay. The plumes merge into a 12-kilometer-wide river of sediment-laden water (flanked by white arrows) that heads almost due north and washes over a large coral reef. The sediment makes the normally turquoise-colored reef look greenish-brown. The plume veers northeastward away from the first reef, and although the plume becomes fainter, it does reach the outer reef. Similar plumes are visible along much of the coastline (visible in the large version of the image).

According to the scientists at Australia's Commonwealth Scientific and Industrial Research Organisation who first publicized them, the images provide proof that scientists monitoring and trying to safeguard the health of Australia's Great Barrier Reef must begin to consider the effect of extreme coastal flooding events that can spread pollution much farther than they previously thought.

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