Lagoon sediments have heterogeneous structure and texture, contain shells and plants and
are often highly bioturbated and disturbed by human activities. In such sediments, the selection of
representative cores and the choice of a subsampling strategy are important but difficult. In this study,
we examine the usefulness of X-ray computed tomography (CT) for inferring sediment features
that will help in making optimal decisions prior to core opening (24 cores from seven lagoons).
Various algorithms (intensity projections, slice thickness, axial and sagittal images, CT number
profiles and volumetric region of interest) are tested to visualise low- and high-density volumes
or objects and to quantify the relations between the average volumetric CT number and the bulk
density of the sediment matrix. The CT number is related mainly to water content and indirectly
to total nitrogen and <16-m grain-size fraction (model R2 = 0.94). The outliers are attributed to a
weak correspondence between the fraction of sediment sampled for water content determination
and the volume of sediment matrix used for CT number measurements in highly heterogeneous
sediment slices. In conclusion, CT is a powerful tool for the initial screening of cores recovered from
heterogeneous lagoon sediments. The adequate use of available algorithms may provide quantitative
information on various sediment features, allowing the purposeful selection of cores and subsamples
for further investigation.
