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Glossary

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2D image or tomograph - are graphical representations of two-dimensional data or a single two-dimensional (height and width) CT image

3D - all 2D images of a sediment core assembled into one large data set so that a true-life image (height, width, and depth) can be viewed from any angle.

3D animations (movies)---- these are a series of 3D views of objects within sediments in which the objects have been rotated every 30 degrees and the view is recorded. This is repeated through a total of 360 degrees. Then all the 3D views are compiled as a movie.

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anthropogenic stresses - human additions, often contaminant metals and/or organics, to natural environments which can stress populations and reduce the number of species

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"bamboo worms"- marine polychaete worms (Family Maldanidae) capable of constructing dense sediment tubes.

bioturbated sediments - sediments that have been mixed by macrofauna

bioturbation - the mixing of sediments by macrofauna

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Computer Aided Tomography (CT) - a powerful imaging technique based upon X-ray penetration of samples to accurately depict and quantify internal structures of varying densities.

CT scanned or scanning - the process of running a sample through a CT machine and making a series of images or sections of the sample

CT numbers (CT#) - when a subject is CT scanned, these are the units in a calibrated scale that relates densities within the subject to X-ray linear-attenuation coefficients.

corers - devices used to collect sediment cores

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ecological state - the interrelationship between organisms and their environments

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flapper valve - a one-way valve, which holds sediment within a corer by suction after sampling

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hydrated sediment - black, watery sediment that often has a strong smell of hydrogen sulfide and sometimes contains gas bubbles.

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macrofauna - animals larger than 0.5mm size living within sediments

macrofaunal tubes and tunnels - the tubes and tunnels or structures and cavities created by macrofauna within sediments

marine sediment communities - all the life forms within specific sediment habitats

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organic loading - the amount of organic matter deposited to a specific area or volume of sediment

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pixel(s) - single points in a 2D image that are each associated with a specific CT # value. Pixels have a height and width, which are usually equal.

pollution gradient - a decease in sediment contaminant level in association with increased distance from a source of pollution

PTTA - the percentage of macrofaunal tubes and tunnels filled with water (CT# range 0 to ~250) in an area of marine sediment

PTTV - the percentage of macrofaunal tubes and tunnels filled with water (CT# range 0 to ~250) in a volume of marine sediment

PVC - is, a type of plastic (poly vinyl chloride) with low X-ray reflective qualities which was used as the construction material for the coring tubes

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sediment habitats - the places where unique assemblages of species associated with specific sediment types and environmental conditions lives and grows

sediment-water interface (SWI) - this is the area in which seawater contacts the surface of the sediment

sediment X-ray attenuation (SXA) - is the average value for any individual CT slice or whole sediment core between the CT# range 251 to 750.

slice thickness - is the uniform distance between sequential slices or images that can be varied from 1.5 to 10 mm on medical scanners.

species - a basic category of individuals having common characteristics distinct from other organisms, which are able to interbreed and are designated by a common name.

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voxels - units of volume that are the equivalent elements to pixels with a depth component, which is related to slice thickness

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X-rays - an electromagnetic ray having an extremely short wavelength that can go through substances that ordinary light cannot penetrate. X-rays are used to diagnose certain diseases and locate breaks in bones prior to treatment.

X-ray imaging - The procedure in which X-rays are used to produce a digitized computer image (tomograph) based on densities within the object that is being CT scanned.

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