The cave-profiler: a simple tool to describe the 3-D structure of inaccessible coral reef cavities

Abstract

Introduction An important part of the bottom of a coral reef consists of dead coral reef framework cavities, this includes the spaces and surfaces under rubble, the undersides of skeletal organisms such as corals, the shaded undersides of overhanging dead or live coral, and deep framework cavities. Cavities are formed below protruding edges of stony corals, in the coral reef framework and are often enlarged by bioeroding organisms. These cavities make up a major part of the volume of the skeleton of a reef. Estimates of the volume encompass 30-75% of total reef volume (Ginsburg, 1983). Cavities provide a surface area for colonization by organisms that may be greater than the horizontally projected reef surface area (Ginsburg, 1983; Gischler & Ginsburg, 1996; Jackson & Winston, 1982). The species composition of these cryptic habitats has been extensively studied (Kobluk & van Soest, 1989; Meesters et al., 1991). Sessile groups such as sponges, crustose coralline and filamentous algae, ascidians, polychaetes, bryozoans, and foraminiferans, usually dominate cryptofauna. Bioeroding organisms, such as clionid