Colonization patterns of mobile cryptic animals into interstices of coral rubble

Coral rubble is one of the characteristic bottom habitats in tropical and subtropical coral reefs. Many mobile organisms inhabit the interstices among coral rubble. Because coral rubble habitats are frequently subjected to physical disturbances, the process of assemblage recolonization is important for maintaining the diversity and productivity in coral reefs. The present study examined the colonization patterns of these mobile organisms by using experimental traps with defaunated coral rubble at 3 areas (Back reef, Seagrass bed, and Nearshore) in a fringing coral reef on Ishigaki Island, Japan. Sixteen mesh trays filled with coral rubble were set at each of the 3 areas; 4 trays were collected after 1, 2, 4, and 8 wk. The experiment was repeated in winter and spring. The number of species that occurred in the trays generally increased with the time period, but detailed examination was difficult because of significant interaction factors, Higher order interactions (season, area, and time period) were also significant for variations in assemblage composition. Temporal and spatial variations in abundances of 15 numerically dominant species (gastropods and decapods) were analyzed by a general linear model with an Akaike's information criterion model selection. Although the patterns of colonization were species specific, initial (<1 wk) and time-dependent (2 to 8 wk) patterns were recognized. These results suggest that a short-distance movement within the local area is the main pathway for the colonization into a disturbed coral rubble habitat. Although seasonal variability in colonization requires consideration, the method using traps with coral rubble provides a standard habitat for quantitative assessment of the assemblage composition of cryptic organisms in coral reefs.