Monitoring bioturbation by a small marine polychaete using microcomputed tomography.

Bioturbation is one of the principle biological processes involved in transporting particles and solutes within sediments, which contributes to the maintenance of biodiversity. In muddy polluted environments, bioturbation may increase pollutant flux at the water-sediment interface, thereby enhancing contaminant bioavailability. The behavior of organisms dictates bioturbation, and gallery shape influences the magnitude of solute transport. Thus, quantitative investigations of gallery shape are fundamental to understanding how pollutant and solute transport is enhanced by bioturbators in muddy sediments. However, there is a lack of tools for quantitatively analyzing gallery geometry, especially for assessing bioturbation and gallery properties through time. Despite the potential of microcomputed tomography (μCT) for quantitative analyses of bioturbation, few such studies have been carried out. Here, we aimed to investigate the potential of μCT for quantitatively assessing the shape and geometric properties of galleries made by small marine polychaetes and their evolution through time in muddy sediments. We focused on Laeonereis acuta (Treadwell, 1923) (Nereididae, Polychaeta), which is a key bioturbator in marine coastal ecosystems. Using 2D and 3D images generated from μCT, we evaluated L. acuta galleries and propose several indexes to quantitatively assess gallery evolution and the role of gallery parameters in bioturbation. Quantitative investigations of polychaete galleries using μCT can assist in monitoring how bioturbation influences sedimentary systems.