Virtual sectioning: a micro-CT and point counting workflow for non-destructive organism quantification

A common method to assess the inner structure of a fossil, a litho- or a bioclasts are thin sections. However, producing thin sections requires the destruction of the examined object, rendering it unavailable for subsequent studies. Moreover, the number of sections that can be obtained from one sample or object is limited, making quantitative analyses difficult.

Herein, we introduce an advanced methodological solution for this issue. A methodological combination of virtual micro-CT cross-sections with a modified point counting approach allows for straightforward and non-destructive identification and quantification of the examined sample.

We demonstrate the benefits of this method through a pilot study examining the quantitative biological composition of calcareous rhodolith matrices from the Arctic Svalbard archipelago. These calcareous matrices can be composed of one or more crustose coralline algal taxa, as well as a mixed assemblage of various invertebrate encrusters. Due to their unique skeletal structure, these biological components can usually be clearly identified in micro-CT scans.

Virtual cross cutting of scanned matrices, quantification of their taxonomic compositions via point counting and subsequent analyses via binomial regression models revealed bathymetrically influenced proportional differences of the rhodoliths.