Abstract

While sediment has been shown in laboratory and small-scale field experiments to be detrimental to coral, we still have a very limited understanding of large-scale effects of sediment on reefs under natural conditions. We conducted benthic surveys on coral reefs at 21 sites in the eastern Caribbean to examine the relationship between reef composition and the size and source (calcareous or terrigenous) of surface sediment adjacent to the reef. Increases in terrigenous sediment were associated with a decrease in the cover of coral, macroalgae and turf algae, and an increase in the cover of sponges. Changes in terrigenous sediment levels were also associated with changes in coral species composition. Porites porites, Madracis mirabilis and Agaricia agaricites all significantly declined with increases in terrigenous sediment, while the hydrozoan Millepora alcicornis increased in cover. We found no relationship between the amount of fine-grained sediment and benthic composition. These results suggest that measuring the composition of surface sediment could be a good alternative to sediment traps in monitoring the effects of sedimentation on corals in this region.

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