The distribution of many macrobenthic species in the back-reef lagoon of Discovery Bay, Jamaica can be related to a gradient in bottom stability. This gradient is defined by increasing rates of biogenic reworking and sediment resuspension in the western part of the lagoon. Infaunal diversity and coral growth decrease in the western, unstable areas. The infauna of the carbonate sand consists mainly of deposit feeders. In the western lagoon, the feeding activities of this group result in high biogenic reworking rates (up to 6-7 cm/week) producing loose surface sediment easily resuspended by waves. A maximum, mean resuspension rate of 19 mg/cm2/day was measured. Instability of the lagoon floor, resulting in high water turbidity, inhibits settlement and growth of most suspension feeders and reduces infaunal diversity and coral growth. Because stability of the soft-bottom is significantly influenced by deposit feeders, our observations represent an extension of the trophic group amensalism principle to tropical nearshore enviornments.