Effects of disturbance: disruption and enhancement of coral reef cryptofaunal populations by hurricanes

Abstract

Samples of solitary cryptofauna were collected from reef habitats before and after Hurricanes David and Frederic struck St. Croix, U.S.V.I. The intertidal beachrock zone suffered severe and sustained damage from waves, sand scouring and moving debris. Most bioeroded cavities in the substrate and several previously abundant cryptic taxa were completely obliterated from this environment for more than 6 months; numbers remained low or the pre-hurricane body size distribution had not been regained by the end of the 2 year study in a number of taxa. In 3 habitats at 2–3 m depths (fringing reef, patch reef, back of the bank barrier reef), some taxa underwent temporary decreases or dislocations, particularly on the fringing reef. Overall, however, this cryptofauna exhibited strong succession, with burrowers and then nestlers increasing above pre-hurricane densities. Many populations of nestlers were still increasing at the end of the 2 year study. Thus, the hurricanes enhanced densities of benthic invertebrates per piece of rubble (probably by providing fresh unburrowed substrate) in these moderately shallow subtidal habitats. On a deeper fore reef (12 m), we detected very few changes in cryptofaunal populations. The enhancement of invertebrate populations in reef habitats with intermediate levels of hurricane diturbance parallels recent findings that some species of corals have evolved colonizing life history tactics which allow them to prosper in moderately disturbed environments. Because the cryptofauna represent an important route of trophic flow (via predatory fishes) through the reef ecosystem, these relatively long term (≧2 y) changes in abundance of invertebrates have important implications for the structure and function of coral reef communities.