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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
In addition, inputs for water temperature (as an influence on development rate), and Secchi disk transparency as an estimator of phytoplankton (midge larval food) abundance were included in the model.
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:
Secchi disk transparency.--The mean summer values for water transparency ([Z.sub.s]) were 94 cm in 2005 and 88 cm in 2006 (Table 2).