Spatial variation in porosity and skeletal element characteristics in apical tips of the branching coral Acropora pulchra (Brook 1891)

Micro-CT scanning techniques were used to investigate fine-scale variation in porosity along branch tips of Acropora pulchra. Porosity variation is a result of progressive thickening of skeletal elements away from the apical tip of branches, rather than changes in the spacing of skeletal elements. A linear fit was found to describe the relationship between distance along the tip and both porosity and skeletal thickness. The slope of the line obtained may relate to branch extension rates and allow retrospective data to be obtained from Acropora specimens. Skeletal morphology examined by 2D and 3D imaging shows a progressive gradation in thickness occurring in the axial corallite wall and thickness changes at a site of incipient branch formation. The application of the micro-CT technique to museum and fossil specimens is illustrated.