Secchi Disk


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Secchi disk

[′sek·ē ‚disk]
(engineering)
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 ?
Field and laboratory methods used for different variables Variable Abbreviation Unit Physical and chemical variables Water level WL cm Secchi disk depth Secchi m Water surface Temp [degrees]C temperature Dissolved oxygen DO mg [L.
Prior to treatment MIM displayed greater turbidity and lower Secchi disk readings than pseudo-control waters (Table 1).
A Secchi disk (SD) was used to determine water transparency (Carlson & Simpson 1996), while wind speed was measured with a Kestrel 2000 Pocket weather meter (Nielsen-Kellerman, Boothwyn, Pennsylvania).
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.
Secchi disk readings (in cm) 1) 19 Sep-6 Oct 1983 31 31 34 2) 31 Oct-16 Nov 1983 37 28 23 3) 19 Jan-10 Feb 1984 3 4 3 4) 26 Mar-15 Apr 1984 9 7 8 5) 6 June-21 June 1984 31 32 30 6) 10 Sep-5 Oct 1984 53 49 52 7a) 8-9 Aug 2000 159 157 172 7b) 27 Sep-3 Oct 2000 169 200 214 Station Means: 1983-84 28 25 26 Station Means: 2000 164 179 193 Period/Date St.
In each account, we include scientific name, common name, total number of specimens (in parentheses), county, river drainage, reach, latitude and longitude, date, number of specimens at that locality, total length, weight when available, method and habitat of capture, temperature of water, turbidity (as depth of Secchi disk, m), and comments.
Transparency was measured in-situ with a Secchi disk according to the standard method (U.
50 Specific conductivity 2005 156 350 51 302 ([micro]S/cm) 2006 91 342 25 320 Total 247 347 43 302 Secchi disk (cm) 2005 146 86 18 50 2006 93 70 15 40 Total 239 80 19 40 Nitrates_N (mg/L) 2005 156 0.
Secchi disk readings were also taken to ensure that the mesocosm depths were consistently in the photic zone.
The effects of a week of continuous rainfall before the October sampling date can be seen in an increase in total P and integrated AGP, a sharp decrease in surface chlorophyll and GCP, and a dramatic reduction in the Secchi disk transparency.