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APPLICATION OF COMPUTER-AIDED TOMOGRAPHY TO VISUALIZE AND QUANTIFY BIOGENIC STRUCTURES IN MARINE SEDIMENTS
Citation:
ROSENBERG, R., E. W. DAVEY, J. GUNNARSSON, K. NORLING, AND M. FRANK. APPLICATION OF COMPUTER-AIDED TOMOGRAPHY TO VISUALIZE AND QUANTIFY BIOGENIC STRUCTURES IN MARINE SEDIMENTS. MARINE ECOLOGY PROGRESS SERIES. Inter-Research, Luhe, Germany, 331:23-34, (2007).
Impact/Purpose:
To use computer-aided tomography and 2D analysis of marine sediment cores to quantify biogenic structures
Description:
We used computer-aided tomography (CT) for 3D visualization and 2D analysis of
marine sediment cores from 3 stations (at 10, 75 and 118 m depths) with different environmental
impact. Biogenic structures such as tubes and burrows were quantified and compared among stations.
Subsequent to CT scanning, the animals and other material in the cores were collected to validate
the image analysis. The shallowest (10 m) station was the most anthropogenically impacted,
having horizontally stratified sediment with few biogenic structures close to the sediment surface but
many shells and relic tubes (i.e. tubes with no connection to the sediment¿water interface) deeper in
the sediment. The sediment at the reference station (75 m) and the deepest station (118 m, previously
impacted by hypoxia) had large numbers of polychaete tubes throughout the sediment down to at
least 30 cm, although many of the tubes deeper down in the sediment were considered relic tubes.
Inhabited tubes had a similar density to shells and seem to persist in the sediment for many years.
Water volume of inhabited tubes was largest close to the sediment-water interface, whereas water
volume in relic tubes was greater between depths of about 3 cm to 30 cm. Many bivalves, particularly
Thyasira equalis, were distributed in the middle and deep part of the sediment at the 75 and 118 m
stations. Water volume of inhabited tubes was greatest at the 118 m station, showing that benthic
fauna recovering from previous hypoxic events can establish burrows and tubes with greater volumes,
and probably with greater impact on biogeochemical processes, than at a reference station
with more stable environmental conditions. This investigation demonstrated that utilization of CT
scanning and software can be applied to visualize and quantify physical and biological structures
within sediment thicknesses of several decimetres.