Substrate composition and adult distribution determme recruitment patterns in a Caribbean brooding coral

This study demonstrates the interactive effect of both substrate composition and adult presence on recruitment and mortality patterns of the earliest life stages in the coral Siderastrea radians in the Florida Keys. Low substrate complexity on a wreck (the 'Benwood') facilitated the location and identification of recently settled coral recruits (< 1 min). Increased adult cover and changes in substrate composition (mainly the presence of crustose coralline algae) enhanced local recruitment, indicating that positive changes in substrate composition acted as an important factor enhancing coral recruitment. Spatial differences in the number of arriving recruits dictated future patterns in local population density as mortality probabilities did not vary spatially. S. radians populations showed the potential to be regulated in a density-dependent manner as suitable settlement substrate was, or could become, limited by (1) its natural availability or (2) preemption by growing adults. Adult removal resulted in a 46% decrease in local (< 1 m(2)) recruitment, indicating that S. radians populations were facultatively closed at this spatial scale. Therefore, the S. radians/Benwood system allows for a detailed description of the processes that create structure in coral populations. Defining the relative contribution of processes that are important in shaping coral population structure contrasts with the more common approach in which only the pattern that results from them is quantified. A process-based approach will allow for a more rigorous investigation of coral population dynamics with obvious benefits for coral reef science and conservation.