In situ settlement rates and early survivorship of hard corals: a good year for a Caribbean reef

Abstract

Coral settlement and early survivorship play an important role in reef resilience. In this study, we investigated the temporal and spatial variation of coral settlement and post-settlement survivorship in different reefs with high and low coral cover in Los Roques Archipelago, Venezuela. In situ estimations of settlement and post-settlement survivorship were compared between months of expected gamete release for broadcasters, and months when larval supply was expected mainly from brooders. Terracotta tiles were deployed at reefs with high (>50%) or low (<15%) hard coral cover, and recruit survivorship was evaluated during their first 4 mo of age by monthly examination of the tiles. Overall, mean (±SD) settlement rates varied between 30 ± 46 and 236 ± 143 ind. m-2 mo-1. At particular reefs and times, settlement rates were up to 7 times higher than previously reported for the Caribbean region. Settlement rates varied between reefs, but were similar between seasons, suggesting that settlement does not increase significantly after a spawning event. Survivorship of settled corals up to 4 mo old varied from 22 to 49% between reefs and was higher at reefs with more coral cover. Our results support the theory that preserving reefs with high coral cover (and maintaining the biological and environmental factors that promote this condition) will result in enhanced settlement and survivorship of coral in its early life-stages, and therefore is a key factor in the conservation of coral reefs.