Changes in the macrobenthos community of a sand flat after erosion

Following a severe erosion of the sand flat at the Telok Aling beach, Penang, the macrobenthos composition changed from being dominated by the gastropod Umbonium vestiarium Lamarck to a predominantly polychaete/bivalve community. Species richness increased to a total of 47 species per 0•25 m2 compared to eight pre-erosion, but the mean population density decreased 10 times to 158–330 individuals per 0•25 m2. All the ambient species, except Echinodiscus bisperforatus Leske, were replaced numerically by the polychaete Diopatra neapolitana Delle Chiaje, Prionospio malmgreni Clarapède and the bivalve Tivela sp. Recovery of U. vestiarium began in May 1989 and attained relatively high densities 6 months later, i.e. about 2 years after their disappearance from the beach.