Habitat selection by larvae influences the depth distribution of six common coral species

The depth range of coral species has often been attributed to post-settlement mortality reflecting different physiological tolerances of species along physical gradients, such as light and water movement. Consequently, the potential of habitat selection by larvae to contribute to these patterns has been largely ignored. To test whether larvae prefer substratum conditioned in the parental habitat, the larvae of 6 common coral species, with contrasting depth distributions, were introduced to aquaria containing settlement tiles conditioned at 2 and 12 m (shallow and deep), plus unconditioned tiles. Goniastrea aspera and G. retiformis, reef-flat species, settled on shallow tiles in densities 4 times greater than on deep tiles. Fungia horrida, a species locally restricted to deeper water, was 6 times more abundant on deep tiles. F. repanda, with a similar distribution, settled exclusively on deep tiles. Platygyra daedalea, a species with a wide depth range, settled preferentially on shallow tiles; however, this preference was much less pronounced than in G. aspera or G. retiformis. Leptoria phyrgia, another species with a wide depth range, was equally abundant on deep and shallow substrata. We conclude that the depth distribution of these species is influenced, in part, by substrate preferences of larvae at settlement.