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246:'s lake water quality assessment programs for some time; lake residents make periodic measurements and submit their readings to state and local agencies. The aggregated longitudinal data are used to reveal general trends in water quality. Similarly, the Indiana Clean Lakes Program trains and relies on volunteers to monitor turbidity in over 80 Indiana lakes using Secchi disks, and uses data submitted by volunteers to monitor lake quality in the state.
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Secchi depth data collected from the sea to a central database. The study's first scientific results were published in 2017. The Secchi Disk study was begun in response to a controversial scientific report that suggested the phytoplankton that influences water transparency had declined by 40% in the oceans between the years 1950 and 2008.
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the disk beyond a point of disappearance, then raising it and lowering it slightly to set the Secchi depth. Another method is to record the depth at which the disk disappears, lower it another few feet, then record the depth at which the disk reappears as it is slowly brought up. The Secchi depth is taken as the average of the two values.
319:"Relazione delle esperienze fatte a bordo della pontificia pirocorvetta l'Immacolata concezione per determinare la trasparenza del mare; Memoria del P. A. Secchi" [Report of the experiments made on board the pontifical steam corvette the Immaculate Conception to determine the transparency of the sea; Memoir of P. A. Secchi].
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A Secchi disk measurement should always be taken off the shady side of a boat or dock between 9:00 and 15:00. The period for best results is between 10:00 and 14:00. The same observer should take Secchi depth measurements, in the same manner, every time. One can approach the measurement by lowering
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In 2013, a team of marine scientists established the global citizen science Secchi Disk program for seafarers to study marine phytoplankton. This ongoing citizen science Secchi Disk study combines the traditional plain white, 30 cm diameter marine Secchi Disk with mobile technology to upload
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The Secchi disk readings do not provide an exact measure of transparency, as there can be errors because of the sun's glare on the water, or one person may see the disk at one depth, but another person with better eyesight may see it at a greater depth. However, it is an inexpensive and
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modified the original all-white Secchi disk to "...a disc about 8 inches in diameter, divided into quadrants painted alternately black and white like the target of a level-rod...". This modified black-and-white Secchi disk is the standard disk used in
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in bodies of water. The disc is mounted on a pole or line and lowered slowly down in the water. The depth at which the disk is no longer visible is taken as a measure of the transparency of the water. This measure is known as the
116:), for the available light averaged over the Secchi disk depth. While used as a variable, the extinction coefficient is also used as a variable for turbidity. The light attenuation coefficient,
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56:. Since its invention, the disk has also been used in a modified, smaller 20 cm (8 in) diameter, black-and-white design to measure freshwater transparency.
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straightforward method of measuring water clarity. Because of the potential for variation between users, methods should be standardized as much as possible.
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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
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Seafarers, Secchi Disk; Lavender, Samantha; Beaugrand, Gregory; Outram, Nicholas; Barlow, Nigel; Crotty, David; Evans, Jake; Kirby, Richard (2017).
717:
Brewin, Robert J. W.; Pitarch, Jaime; Dall’Olmo, Giorgio; van der Woerd, Hendrik J.; Lin, Junfang; Sun, Xuerong; Tilstone, Gavin H. (2023-03-07).
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can operate at depths of 150 m (492 ft) and can record visible, ultraviolet, and infrared parts of the spectrum.
83:. A plain white, 30 cm (12 in) diameter Secchi disk remains the standard design used in marine studies. In 1899,
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Secchi disk measurements do not indicate how attenuation changes with depth or particular wavelengths of light. Submarine
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Lee, ZhongPing; Shang, Shaoling; Hu, Chuanmin; Du, Keping; Weidemann, Alan; Hou, Weilin; Lin, Junfang; Lin, Gong (2015).
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719:"Evaluating historic and modern optical techniques for monitoring phytoplankton biomass in the Atlantic Ocean"
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Boyce, Daniel G.; Lewis, Marlon R.; Worm, Boris (2010). "Global phytoplankton decline over the past century".
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576:"Seafarer citizen scientist ocean transparency data as a resource for phytoplankton and climate research"
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Different kinds of Secchi disks. A marine style on the left and the freshwater version on the right
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Secchi App – The global scientific experiment by seafarers to study the marine phytoplankton
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Cole, Gerald A. (1994). Textbook of
Limnology. 4th ed. Prospect Heights: Waveland Press Inc.
39:, is a plain white, circular disk 30 cm (12 in) in diameter used to measure water
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446:"On the Universality of the Poole and Atkins Secchi Disk: Light Extinction Equation"
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have their own light sources and can measure transparency with scientific accuracy.
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Cialdi, M. and Secchi, P. A. (1865). "Sur la
Transparence de la Mer."
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The original Secchi disk was a plain white disk and was used in the
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Circular disk used to measure water transparency or turbidity
764:"Why does the Secchi disk disappear? An imaging perspective"
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Secchi disk measurements have been an integral component of
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Similar disks, with a black-and-yellow pattern, are used as
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Journal of the
European Optical Society: Rapid Publications
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Hou, Weilin; Lee, Zhongping; Weidemann, Alan D. (2007).
850:"Secchi disk science: Visual optics of natural waters1"
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532:"Indiana Clean Lakes Program – Volunteer Monitoring"
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The modified Secchi disk design used in fresh water
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207:, the intensity of light at the ocean surface.
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180:{\displaystyle {I_{z} \over I_{0}}=e^{-kz},}
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363:Comptes Rendu de l'Acadamie des Sciences.
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484:Handbook of Common Methods in Limnology
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378:New York: John Wiley & Sons, 73–5.
774:(6). The Optical Society: 2791–3502.
635:"Ocean greenery under warming stress"
418:"Why a Black and White Secchi Disk?"
120:, can then be used in a form of the
893:"On the history of the Secchi disc"
295:"On the history of the Secchi disc"
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848:Preisendorfer, Rudolph W. (1986).
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196:, the intensity of light at depth
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376:The Microscopy of Drinking-Water.
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985:Oceanographic instrumentation
891:Wernand, M. R. (2010-04-27).
811:Remote Sensing of Environment
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92:(freshwater) investigations.
903:. European Optical Society.
633:Schiermeier, Quirin (2010).
601:10.1371/journal.pone.0186092
395:. 1999-08-28. Archived from
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723:Frontiers in Marine Science
444:; Gilbert, R. Gene (1974).
374:Whipple, George C. (1899).
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854:Limnology and Oceanography
736:10.3389/fmars.2023.1111416
557:"Marine Secchi Disk study"
450:British Ecological Society
389:"What is the SECCHI disk?"
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867:10.4319/lo.1986.31.5.0909
824:10.1016/j.rse.2015.08.002
486:St. Louis: C.V. Mosby Co.
35:), as created in 1865 by
939:Secchi Disk Transparency
935:at Encyclopedia of Earth
910:10.2971/jeos.2010.10013s
817:. Elsevier BV: 139–149.
52:and is related to water
510:Encyclopædia Britannica
482:Lind, Owen, T. (1979).
110:attenuation coefficient
729:. Frontiers Media SA.
506:"Undersea exploration"
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114:extinction coefficient
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949:Secchi disk simulator
860:(5). Wiley: 909–926.
648:10.1038/news.2010.379
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956:at The Secchi Dip-In
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327:(1): 205–238. 1864.
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684:10.1038/nature09268
676:2010Natur.466..591B
592:2017PLoSO..1286092S
333:1864NCim...20..205.
270:Trophic state index
561:www.secchidisk.org
341:10.1007/BF02726911
306:2014-04-26 at the
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69:crash-test dummies
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980:Fisheries science
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427:2012-07-05
403:2023-03-18
281:References
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790:1094-4087
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516:1 October
393:mlswa.org
349:182945407
244:Wisconsin
240:Minnesota
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