ROLE OF LIGHT-INTENSITY AND SPECTRAL QUALITY IN CORAL SETTLEMENT - IMPLICATIONS FOR DEPTH-DEPENDENT SETTLEMENT

On coral reefs scleractinian corals show strong patterns of vertical z onation, yet the underlying mechanisms creating and maintaining vertic al zonation are poorly understood. Here we examine the potential contr ibution of light-dependent settlement in scleractinian coral planulae to patterns of vertical zonation. The effect of intensity and spectral quality of light on the settlement of six species of scleractinian co rals (Goniastrea favulus Dana, Goniastrea aspera Verrill, Acropora ten uis Dana, Oxypora lacera Verrill, Montipora peltiformis Bernard, and P latygyra daedalea Ellis and Solander) with contrasting depth distribut ions was examined in laboratory trials. Light-dependent settlement was shown by planulae from five of the six species examined. Planulae fro m individual species showed a response to either Light quality or Ligh t quantity, but not both. Settlement patterns shown by planulae from a ll six species were consistent with the vertical distribution patterns of adults in the field. Settlement of planulae from con-generic speci es with similar adult distribution patterns did not respond to variati on in light intensity or spectral quality in a uniform manner, indicat ing the optimal light environment for settlement is species specific. The settlement patterns shown by planulae from five of the six species examined were more complex than required for selection of cryptic or exposed micro-habitats at settlement. The ecological function of such complex responses to light at settlement may be to identify optimum ha bitats for adult survival. (C) 1998 Elsevier Science B.V.