High density (HD) bands mark annual cycles of growth in X- radiographs of reef coral skeletons and presumably form due to physiological response to seasonal cycles of temperature and light. However, the mechanism of formation has not been established for any coral. The HD band is usually used to define the annual band, and thus understanding its formation, and the controls on variability in its timing is important. In the research, a conceptual model of how density bands form, based on physiological and morphological data obtained with earlier NSF funding, is will be developed. Four specific aspects of the work will include: (1) development of a mechanistic mathematical model for the formation of the HD band of Montastrea annularis, a major coral used in paleoclimate work; (2) conducting an in situ experiment to test the validity of the model; (3) evaluation of the genetic vs. environmental components of variation in time of formation of the HD band; and (4) assessment of the variation among corals in the relationship between HD bands and stable isotope profiles. This study will provide the type of environmental physiological data needed for the precise use of coral density bands for paleoclimatology.
