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Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement


The effect of European settlement on water quality in the Great Barrier Reef of Australia is a long-standing and controversial issue1,2,3,4,5,6. Erosion and sediment transport in river catchments in this region have increased substantially since European settlement6,7,8,9,10, but the magnitude of these changes remains uncertain1,2,3,4,5,6,7,8,9,10. Here we report analyses of Ba/Ca ratios in long-lived Porites coral from Havannah Reef—a site on the inner Great Barrier Reef that is influenced by flood plumes from the Burdekin river—to establish a record of sediment fluxes from about 1750 to 1998. We find that, in the early part of the record, suspended sediment from river floods reached the inner reef area only occasionally, whereas after about 1870—following the beginning of European settlement—a five- to tenfold increase in the delivery of sediments is recorded with the highest fluxes occurring during the drought-breaking floods. We conclude that, since European settlement, land-use practices such as clearing and overstocking have led to major degradation of the semi-arid river catchments, resulting in substantially increased sediment loads entering the inner Great Barrier Reef.

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Figure 1: Map showing the location of the central Great Barrier Reef (after Belperio7).
Figure 2: The coral Ba/Ca record of suspended sediment into the GBR by the Burdekin river over approximately the past 250 years.
Figure 3: Plot of the maximum Ba/Ca flood peak height versus the maximum weekly Burdekin river discharge for flood events from 1921 to the present.

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This study has greatly benefited from developments in laser ablation instrumentation undertaken by S. Eggins, M. Shelley and L. Kinsley. Appreciation is extended to D. Sinclair whose initial work stimulated this research. We thank M. Devlin, D. Haynes, K. Fabricius, J. Brodie and J. Marshall for assistance in undertaking marine fieldwork and discussions on terrestrial impacts in the Great Barrier Reef. We thank P. Isdale for collecting the Havannah coral core. We are also grateful to A. Chivas for constructive comments on the manuscript. Data can be accessed at the World Data Centre for Paleoclimatology at This research is supported by a grant from the ARC.

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Correspondence to Malcolm McCulloch.

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McCulloch, M., Fallon, S., Wyndham, T. et al. Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement. Nature 421, 727–730 (2003).

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