A simple instrument used to measure the transparency of surface water bodies such as lakes and reservoirs. A Secchi disk is a metal, plastic, or wooden disk that is 8–12 in (20–30 cm) in diameter. It may be white or have alternating black and white quadrants. A long calibrated rope is attached to the center of the disk. Researchers use the disk by lowering it into the water, usually from the shaded side of a boat, and measuring the depth at which it just disappears from sight. The disk is then lowered a little more and then raised until it reappears. The average of the depths at which the disk disappears and then reappears is known as the Secchi depth. The amount of sediment , algae, and other solids in the water affects clarity and depth of light penetration and thus, Secchi depth. Scientists use this measure of transparency as a simple indication of water quality , often by comparing Secchi depth measurements over a period of time to track changes in the clarity of a particular water body.
"Secchi Disk." Environmental Encyclopedia. . Encyclopedia.com. (July 23, 2019). https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/secchi-disk
"Secchi Disk." Environmental Encyclopedia. . Retrieved July 23, 2019 from Encyclopedia.com: https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/secchi-disk
Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).
Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.
Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:
Modern Language Association
The Chicago Manual of Style
American Psychological Association
- Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
- In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.