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Different kinds of Secchi disks. A marine style on the left and the freshwater version on the right. The Secchi depth is reached when the reflectance equals the intensity of light backscattered from the water. 1.7 divided into this depth in metres yields an attenuation coefficient (also called an extinction coefficient), for the available light averaged over the Secchi disk depth.
The following other wikis use this file: Usage on ca.wikipedia.org Disc de Secchi; Usage on cs.wikipedia.org Secchiho deska; Usage on de.wikipedia.org
Relationships between Trophic State Index, chlorophyll, phosphorus, Secchi depth, and trophic class (after Carlson 1996) [4] Trophic State Index Chlorophyll (μg/L) Phosphorus (μg/L) Secchi depth (m) Trophic Class < 30—40 0—2.6 0—12 > 8—4 Oligotrophic or hipotrophic 40—50 2.6—7.3 12—24 4—2 Mesotrophic 50—70 7.3—56 24—96
Different kind of Secchi disks. According to FIMR ((Finnish)[1]), a ~30 cm white disk is conventionally used in oceanography. Original : en:Image:Secchi disks.svg
Secchi depth is the depth at which a disk is no longer visible to the human eye. This measurement was created in 1865 and represents one of the oldest oceanographic methods. [23] [24] To measure Secchi depth, a white or black-and-white disk is mounted on a pole or line and lowered slowly down in the water. The depth at which the disk is no ...
The Secchi disk has the advantages of integrating turbidity over depth (where variable turbidity layers are present), being quick and easy to use, and inexpensive. It can provide a rough indication of the depth of the euphotic zone with a 3-fold division of the Secchi depth , however this cannot be used in shallow waters where the disk can ...
The standard measurement for underwater visibility is the distance at which a Secchi disc can be seen. The range of underwater vision is usually limited by turbidity. In very clear water visibility may extend as far as about 80m, [18] and a record Secchi depth of 79 m has been reported from a coastal polynya of the Eastern Weddell Sea ...
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