Off-reef transport of coral fragments at Lizard Island, Australia

Hughes, T.P.

Abstract

The generation and movement of coral rubble is important to the sedimentary budget of a reef, in sediment facies development, and in the promotion of reef growth. This study examined the rate of down-slope transport of live and dead coral fragments from shallow reef fronts at Lizard island, on the Great Barrier Reef, Australia. Ten large (1 m²) collecting trays were deployed and cleared annually for 4 years at each of two sites at the base (8-12 m depth) of the steeply-sloping fringing reef. The rate of export of coral fragments down the reef slope was very high: an average of 132 fragments weighing 1.87 kg was recorded each year per meter of reef front. A mean of 2.25% of the fragments (representing 43 species) was five in the trays at each annual census, yielding an average rate of colonization onto the reef slope of 2.7 live fragments per meter of reef front per year. Reworking of hard calcareous substrates towards the slope promotes reef growth by two mechanisms: (1) passive dispersal of live coral fragments to peripheral, soft-sediment habitats that are unsuitable for larval settlement, and (2) subsequent colonization of rubble by coral larvae. There were no major storms during the course of the study, indicating that significant down-slope transport of fragments can occur even in the absence of cyclones.

Journal

Marine Geology

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Volume

157

ISBN/ISSN

1872-6151

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Issue

1-2

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Publisher

Elsevier

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DOI

10.1016/S0025-3227(98)00187-X