X-ray microanalysis and the axial elemental composition in alcyonacean octocorals (anthozoa, octocorallia)

Octocorals are among the most abundant and diverse organisms in the ocean. These animals are present in every ocean and can be found from the intertidal zone (0 m) to abyssal depths (over 6000 m). Gorgonians are octocorals with a solid, internal axis. There are three axial types that differentiate gorgonians: scleraxonians, holaxonians, and calcaxonians. This study analyzed the variation in axial chemical composition within these three gorgonian axis types with x-ray microanalysis, by using quantitative energy dispersive x-ray spectrometry (EDS). EDS successfully quantified the elemental composition of eleven gorgonian octocoral axes. Scleraxonian elemental composition showed significant similarity and suggests that, based specially on axial elemental composition, scleraxonians comprise a unified group. However, holaxonian and clacaxonian elemental compositions were significantly different within each group and thus do not represent concise grouping by axis type.