Components of benthic communities in a coral reef system subjected to elevated particulate organic loading show differential biomass responses to this food resource. The macrofaunal biomass of the hard-bottom cryptofaunal community was elevated under such loading; termination of the nutrient input resulted in a rapid decline in hard substratum cryptofaunal biomass. In contrast, adjacent soft substratum communities showed minor variation in macrofaunal biomass. Such pronounced changes in hard-bottom communities to nutrient loading suggests that these endolithic components may be more responsive to and closely regulated by food than are their soft substratum counterparts. Thus, hard-bottom communities probably yield more information than soft-bottom assemblages in sewage (nutrient loading) studies on coral reefs.