High, but localized recruitment of Montastraea annularis complex in St. John, United States Virgin Islands

This study describes relatively high recruitment of Montastraea annularis complex (hereafter, MAC) on the shallow reefs (≤9 m depth) along 4 km of the south coast of St. John that have been censused for 16 years. Before 2008, the density of juvenile MAC along this stretch of coast was <0.068 colonies m⁻² (and often <0.032 colonies m⁻²), but in 2008 it increased to 0.152 colonies m⁻² and remained at 0.116 colonies m⁻² in 2009. These densities were driven by only 7–9 colonies year⁻¹, but against the long-term context of weak recruitment and declining cover of this taxon, the densities are notable. In 2009, the spatial extent of the surveys was expanded to 47 km, along the north, east, and south coasts of St. John. This larger effort demonstrated that MAC recruitment was localized to the initial 4 km surveyed; outside this area, the mean density was 0.010 juvenile colonies m⁻². These results demonstrate that MAC is still capable of recruitment at rates similar to those of the 1970s, but the highly limited spatio-temporal extent of the effect is unlikely to appreciably alter the declining population trajectories of this taxon.