Sediment-Profile Imaging

Brief description


Sediment-profile imaging (SPI) is a benthic sampling technique that produces undisturbed, vertical cross-section photographs (in situ profiles) of the upper 15 to 20 cm of the seafloor surface. Employing a specially designed camera and frame, SPI is a discrete sampling technique used for rapid collection, interpretation, and mapping of data on physical and biological seafloor characteristics.

See NOAA's summary table at summary view of Sediment -Profile Imaging technique (471 KB PDF).


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SPI

A sediment profile imaging (SPI) system uses a camera and prism mounted on a frame to take a picture of where the seafloor and water meet. This instrument is lowered to the bottom from a ship, then takes cross-section photographs of the upper 15-20 cm of the surface of the seafloor. It is a useful tool for identifying features such as sediment grain size, infauna, sub-surface methane pockets, dredged material deposition, and hypoxic conditions.

The imaging faceplate is in direct contact with the sediments, so SPI can be used in turbid waters. The sediment profile imaging (SPI) system is designed to photograph the sediment-water interface without creating disturbance. A sharp-edged prism cuts cleanly into the sediment to a depth of 15 to 20 cm. The camera is mounted in the top of the prism, and a mirror is used to reflect the sediment image to the camera from the vertical faceplate. Since the sediment is right up against the faceplate, lack of water clarity is never a limitation on this optical method.

Advantages

Sediment profile imaging is a useful tool for rapidly collecting data and analyzing a suite of seafloor parameters. These include: sediment grain size, camera prism penetration depth (an indirect measure of sediment density), roughness of the sediment-water interface, transition between oxygenated surface sediments and underlying sediments with little or no oxygen (called the apparent redox potential discontinuity layer), biological successional stage, and presence of methane gas bubbles, burrows, fauna, and dredged material.

More details are given in the NOAA SPI Benthic Habitat Mapping Site.

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