Wednesday 20 March 2013

The vanishing Corals of Pelorus Island.

Corals on Australia's Great Barrier Reef, as in other parts of the world, are known to be in trouble, with declining Coral coverage, diebacks, bleaching events and replacement of Corals by Macroalgae (Seaweed) on much of the reef. Unfortunately, recording of Coral fitness on the reef in an organized way only began in 1980, by which time the Corals were already suffering severe problems, meaning that attempts to understand what has caused this are highly speculative, since it is not clear when it started.

In an attempt to resolve this problem, a team of scientists led by George Roff of the School of Biological Sciences and Australian Research Council Centre of Excellence for Coral Reef Studies at the University of Queensland, drilled a number of cores into the (severely depleted) Coral Reefs on Pelorus Island, between the main Barrier Reef and the coast of Queensland, in order to build up a chronology of the reef's decline, the results of the study being published in a paper in the Proceedings of the Royal Academy Series B Biological Sciences on 7 November 2012.

The location of Pelorus Island. Roff et al. 2012.

Roff et al. found that coral dieback on Pelorus Island began between 1928 and 1944, and suggest that this may be linked to sediment flow from the Burdekin River. The area was settled by European colonists from the 1870s onwards, with a subsequent change in land use as forested land was cleared to make way for agriculture and livestock raising. This lead to increased soil erosion, particularly in years when there was draught or flooding. This was compounded from 1930 onwards, when the use of agricultural fertilizers became widespread in the region.

Sediment runoff from the Burdekin River. NASA/Earth Observatory.

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