The Impact of Sediment on the Great Barrier Reef

The Impact of Sediment on the Great Barrier Reef

By: Kellie Brenton

Figure 1. Aerial view of sediment transport by stream runoff.

Recently, scientists have begun to notice there are large amounts of sediment being forced into oceans near the Great Barrier Reef as a result of rivers in the surrounding area. At first, scientists didn’t think too much about what damages stream runoff could cause, but new research is showing that the sediment transported by the runoff is actually harmful to the reefs. The research has shown that large river flood events are the reason for the high amounts of sediment being transported into the ocean.

Sediment that reaches the coral reefs is one of the biggest dangers to the health and stability of the offshore reefs. Sunlight is one of the major factors controlling the overall beauty of the coral reefs, but when sediment clouds the water, the sunlight can’t reach the algae that grows on the reefs to make them beautiful. The survival of the algae depends on sunlight. The sediment stays in the suspended load for up to several months, damaging not only the survival rate of the algae, but also of the sea grasses that fish and others eat to survive. The sediment trapped in the water could potentially lead to the death of fish and other mammals if the sea grasses begin to die.

The scientists in Australia have come to the conclusion that the fine sediment that is able to be transported to the ocean through flood events, is the sediment that comes from land erosion. There are scientific models showing that there has been an increase of land erosion since human settlement and the start of agricultural practices. Since the news came out that the reefs are being damaged by sediment, people have taken action to retain more of the sediment in catchments near the rivers.