A new method for three-dimensional visualization and quantification of biogenic structures in aquatic sediments using axial tomodensitometry

Biogenic structures formed by the activity of macro- and meiobenthic organisms exert a great influence on the physical, chemical, and biological properties of sediments. Although bioturbation processes are recognized as ecologically important, the characterization and quantification of biogenic structures produced by benthic organisms remain difficult. Several techniques (e.g., resin casting, X-radiography) were previously used to quantify these structures. However, due to a lack of definition, entire burrows, including fine structures created by meiobenthic and small macrobenthic species, could not be identified with precision. Here, we show how axial tomodensitometry (CT scan) can be used to visualize biogenic structures and organic matter in three dimensions with high resolution. Further, a simple method for calculating the space occupied by biogenic structures at given depths is developed, based on comparisons of the densities of biogenic structures with those of surrounding sediments. Other potential uses of the CT scan technique in studying benthic ecology are discussed.