3D visualization and quantification of marine benthic biogenic structures and particle transport utilizing computer-aided tomography

Abstract

Computer-aided tomography was used to visualize and quantify biogenic structures (e.g. burrows, shells) in 3 dimensions (3D) by scanning 9 replicate cores obtained from a 41 m deep station in the Gullmarsfjord (Skagerrak, western Sweden). The main objective was to visualize and quantify the biogenic structures and their volumes in the sediment. In addition, the particle transport was studied by adding an aluminum oxide tracer to the sediment -water interface (SWI), which was analysed after 57, 80 and 128 h, in 3 replicate cores each time. A new software programme was developed for rapid and accurate analysis. The fauna in the cores, analysed after scanning, were dominated by the brittle stars Amphiura filiformis and A. chiajei. The volumes of 'active' biogenic structures, defined as connecting to the SWI, were generally greatest close to the interface with some secondary peaks, probably related to the position of the disc chamber of the brittle stars. A mean volume of 560 cm 3 of biogenic structures per m 2 of sediment surface was recorded within the sediment (down to a mean depth of 137 mm, where the biogenic structures ceased to be 'active'). Ejection of particles to the SWI (mounding) was calculated to be between 4 and 40 mm 3 h -1 .

Quantification of sediment reworking rates in bioturbation research: a review

“…This method measures the density of elementary (sediment) cells called voxels. It can be used as a tracer method, if the tracer particles are slightly different in density from the surrounding sediment (Rosenberg et al 2008). This new approach is promising, but still presents 2 difficulties: (1) Selective dispersal, as density differences between the tracer and the surrounding sediment may affect sediment reworking (see above).…”

“…water, sediment, tracer particles). Rosenberg et al (2008) tried to resolve this resolution problem when using aluminium as a tracer to study the sediment reworking of an Amphiura filiformis community. They proposed to consider that voxels with a density compatible with the presence of aluminium indeed corresponded to reworked aluminium only if they were connected to the sediment -water interface through a continuous series of water and/or aluminium voxels (i.e.…”

Influence of the mode of macrofauna-mediated bioturbation on the vertical distribution of living benthic foraminifera: First insight from axial tomodensitometry

“…This technical development has resulted in greater use of CT-scans being made in both marine (e.g. Perez et al, 1999;Mermillod-Blondin et al, 2003;Rosenberg et al, 2007;Mazik et al, 2008;Rosenberg et al, 2008) and terrestrial studies (Daniel et al, 1997). Computed tomography is now recognized to be an efficient tool for the three-dimensional exploration of biogenic structures and accurate volume quantification in soil and sediments.…”

Characterizations of how species mediate ecosystem properties require more comprehensive functional effect descriptors

“…Whilst context-dependent changes in species behaviour (e.g. in relation to food supply18, tidal periodicity25, temperature26 or photoperiod27) and key features of biogenic structures, including length, diameter, volume and configuration, have been described in detail for individual species282930 and communities31, there is a paucity of information on whether such information is of utility in distinguishing the functional standing of individual species323334. Here, we investigate the functional effect of three co-occurring species of benthic invertebrates, alone and in mixture, using a combination of high-resolution sediment profile imaging and computerized tomography that, together, allow multiple components of particle and fluid transport to be assessed alongside important aspects of burrow morphology at functionally relevant scales (microns to mm).…”