Secchi Disk

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Secchi disk

[′sek·ē ‚disk]
An opaque white disk used to measure the transparency or clarity of seawater by lowering the disk into the water horizontally and noting the greatest depth at which it can be visually detected.

Secchi Disk


an instrument for measuring water transparency in a body of water. A white disk 30 cm in diameter, it is held horizontally and lowered into the water on a rope until it is no longer visible. The depth, in meters, at which it ceases to be visible is taken as a measure of the water transparency. The disk is named after A. Secchi, who measured the transparency of sea water by this method in 1865.

References in periodicals archive ?
Johns River) for the month prior to sampling was used (representing the approximate development time of immatures that would be collected during the sample effort), with water temperature and Secchi disk transparency data collected during the same prior month.
Trophic conditions of the General Sampaio Reservoir were derived from Trophic State Index (TSI) proposed by Carlson (1977) modified by Toledo Junior (1990), which incorporates Secchi disk transparency, total phosphorus and chlorophyll a as indicators (or variables) of trophic state, based on equations 1, 2 and 3:
Prairie Creek Reservoir 2005 * 2006 [dagger][dagger] Secchi disk transparency (m) 0.