The Secchi disk (or Secchi disc), as created in 1865 by Angelo Secchi, is a plain white, circular disk 30 cm (12 in) in diameter used to measure water transparency or turbidity 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 Secchi depth and is related to water turbidity. 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.
The modified Secchi disk design used in fresh water
The original Secchi disk was a plain white disk and was used in the Mediterranean Sea.[1][2] A plain white, 30 cm (12 in) diameter Secchi disk remains the standard design used in marine studies. In 1899, George C. Whipple 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...".[3][4] This modified black-and-white Secchi disk is the standard disk used in limnology (freshwater) investigations.[5][6]
Secchi depthedit
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. While used as a variable, the extinction coefficient is also used as a variable for turbidity. The light attenuation coefficient, k, can then be used in a form of the Beer–Lambert law,
to estimate Iz, the intensity of light at depth z from I0, the intensity of light at the ocean surface.[7]
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 straightforward method of measuring water clarity. Because of the potential for variation between users, methods should be standardized as much as possible.
A Secchi disk measurement should always be taken off the shady side of a boat or dock between 9:00 and 15:00.[8] 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 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.[9]
Secchi disk measurements do not indicate how attenuation changes with depth or particular wavelengths of light. Submarine photometers can operate at depths of 150 m (492 ft) and can record visible, ultraviolet, and infrared parts of the spectrum. Turbidimeters and Transmissometers have their own light sources and can measure transparency with scientific accuracy.[10]
Applicationsedit
Secchi disk measurements have been an integral component of Minnesota's and Wisconsin'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.[11]
In 2013, a team of marine scientists established the global citizen science Secchi Disk program for seafarers to study marine phytoplankton.[12] This ongoing citizen science Secchi Disk study combines the traditional plain white, 30 cm diameter marine Secchi Disk with mobile technology to upload Secchi depth data collected from the sea to a central database. The study's first scientific results were published in 2017.[13] 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.[14][15]
^"On the history of the Secchi disc". www.jeos.org. 2014-04-26 at the Wayback Machine
^"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]. Il Nuovo Cimento. 20 (1): 205–238. 1864. Bibcode:1864NCim...20..205.. doi:10.1007/BF02726911. S2CID 182945407.
^Cialdi, M. and Secchi, P. A. (1865). "Sur la Transparence de la Mer." Comptes Rendu de l'Acadamie des Sciences. 61: 100–104.
^Whipple, George C. (1899). The Microscopy of Drinking-Water. New York: John Wiley & Sons, 73–5.
^. mlswa.org. 1999-08-28. Archived from the original on 2012-08-14. Retrieved 2023-03-18.
^"Why a Black and White Secchi Disk?". www.nalms.org. Retrieved 2012-07-05.
^Idso, Sherwood B.; Gilbert, R. Gene (1974). "On the Universality of the Poole and Atkins Secchi Disk: Light Extinction Equation". British Ecological Society. 11 (1): 399–401. doi:10.2307/2402029. JSTOR 2402029.
^Lind, Owen, T. (1979). Handbook of Common Methods in Limnology St. Louis: C.V. Mosby Co.
^Cole, Gerald A. (1994). Textbook of Limnology. 4th ed. Prospect Heights: Waveland Press Inc.
^"Undersea exploration". Encyclopædia Britannica. 2008. Retrieved 1 October 2008 – via Encyclopædia Britannica Online.
^"Indiana Clean Lakes Program – Volunteer Monitoring". www.indiana.edu. Retrieved 9 February 2011.
^Seafarers, Secchi Disk; Lavender, Samantha; Beaugrand, Gregory; Outram, Nicholas; Barlow, Nigel; Crotty, David; Evans, Jake; Kirby, Richard (2017). "Seafarer citizen scientist ocean transparency data as a resource for phytoplankton and climate research". PLOS ONE. 12 (12): e0186092. Bibcode:2017PLoSO..1286092S. doi:10.1371/journal.pone.0186092. PMC5718423. PMID 29211734.
^Schiermeier, Quirin (2010). "Ocean greenery under warming stress". Nature. doi:10.1038/news.2010.379.
^Boyce, Daniel G.; Lewis, Marlon R.; Worm, Boris (2010). "Global phytoplankton decline over the past century". Nature. 466 (7306): 591–596. Bibcode:2010Natur.466..591B. doi:10.1038/nature09268. PMID 20671703. S2CID 2413382.
Further readingedit
Brewin, Robert J. W.; Pitarch, Jaime; Dall’Olmo, Giorgio; van der Woerd, Hendrik J.; Lin, Junfang; Sun, Xuerong; Tilstone, Gavin H. (2023-03-07). "Evaluating historic and modern optical techniques for monitoring phytoplankton biomass in the Atlantic Ocean". Frontiers in Marine Science. Frontiers Media SA. 10. doi:10.3389/fmars.2023.1111416. hdl:10871/132642. ISSN 2296-7745.
Hou, Weilin; Lee, Zhongping; Weidemann, Alan D. (2007). "Why does the Secchi disk disappear? An imaging perspective". Optics Express. The Optical Society. 15 (6): 2791–3502. doi:10.1364/oe.15.002791. ISSN 1094-4087. PMID 19532517.
Lee, ZhongPing; Shang, Shaoling; Hu, Chuanmin; Du, Keping; Weidemann, Alan; Hou, Weilin; Lin, Junfang; Lin, Gong (2015). "Secchi disk depth: A new theory and mechanistic model for underwater visibility". Remote Sensing of Environment. Elsevier BV. 169: 139–149. doi:10.1016/j.rse.2015.08.002. ISSN 0034-4257. OCLC 5867529207.
Preisendorfer, Rudolph W. (1986). "Secchi disk science: Visual optics of natural waters1". Limnology and Oceanography. Wiley. 31 (5): 909–926. doi:10.4319/lo.1986.31.5.0909. ISSN 0024-3590. OCLC 5718371060.
Wernand, M. R. (2010-04-27). "On the history of the Secchi disc". Journal of the European Optical Society: Rapid Publications. European Optical Society. 5. doi:10.2971/jeos.2010.10013s. ISSN 1990-2573.
External linksedit
Secchi disk at Encyclopedia of Earth
Secchi Disk Transparency
EPA OWOW
Secchi disk simulator
The Secchi Disk at The Secchi Dip-In
Secchi App – The global scientific experiment by seafarers to study the marine phytoplankton
February 18, 2024
secchi, disk, secchi, disc, created, 1865, angelo, secchi, plain, white, circular, disk, diameter, used, measure, water, transparency, turbidity, bodies, water, disc, mounted, pole, line, lowered, slowly, down, water, depth, which, disk, longer, visible, taken. The Secchi disk or Secchi disc as created in 1865 by Angelo Secchi is a plain white circular disk 30 cm 12 in in diameter used to measure water transparency or turbidity 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 Secchi depth and is related to water turbidity 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 The modified Secchi disk design used in fresh waterSimilar disks with a black and yellow pattern are used as fiducial markers on vehicles in crash tests crash test dummies and other kinetic experiments Contents 1 History 2 Secchi depth 3 Applications 4 See also 5 References 6 Further reading 7 External linksHistory editThe original Secchi disk was a plain white disk and was used in the Mediterranean Sea 1 2 A plain white 30 cm 12 in diameter Secchi disk remains the standard design used in marine studies In 1899 George C Whipple 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 3 4 This modified black and white Secchi disk is the standard disk used in limnology freshwater investigations 5 6 Secchi depth edit nbsp Different kinds of Secchi disks A marine style on the left and the freshwater version on the rightThe 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 While used as a variable the extinction coefficient is also used as a variable for turbidity The light attenuation coefficient k can then be used in a form of the Beer Lambert law I z I 0 e k z displaystyle I z over I 0 e kz nbsp to estimate Iz the intensity of light at depth z from I0 the intensity of light at the ocean surface 7 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 straightforward method of measuring water clarity Because of the potential for variation between users methods should be standardized as much as possible A Secchi disk measurement should always be taken off the shady side of a boat or dock between 9 00 and 15 00 8 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 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 9 Secchi disk measurements do not indicate how attenuation changes with depth or particular wavelengths of light Submarine photometers can operate at depths of 150 m 492 ft and can record visible ultraviolet and infrared parts of the spectrum Turbidimeters and Transmissometers have their own light sources and can measure transparency with scientific accuracy 10 Applications editSecchi disk measurements have been an integral component of Minnesota s and Wisconsin 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 11 In 2013 a team of marine scientists established the global citizen science Secchi Disk program for seafarers to study marine phytoplankton 12 This ongoing citizen science Secchi Disk study combines the traditional plain white 30 cm diameter marine Secchi Disk with mobile technology to upload Secchi depth data collected from the sea to a central database The study s first scientific results were published in 2017 13 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 14 15 See also editForel Ule scale Siemens star Trophic state index Water qualityReferences edit On the history of the Secchi disc www jeos org Archived 2014 04 26 at the Wayback Machine 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 Il Nuovo Cimento 20 1 205 238 1864 Bibcode 1864NCim 20 205 doi 10 1007 BF02726911 S2CID 182945407 Cialdi M and Secchi P A 1865 Sur la Transparence de la Mer Comptes Rendu de l Acadamie des Sciences 61 100 104 Whipple George C 1899 The Microscopy of Drinking Water New York John Wiley amp Sons 73 5 What is the SECCHI disk mlswa org 1999 08 28 Archived from the original on 2012 08 14 Retrieved 2023 03 18 Why a Black and White Secchi Disk www nalms org Retrieved 2012 07 05 Idso Sherwood B Gilbert R Gene 1974 On the Universality of the Poole and Atkins Secchi Disk Light Extinction Equation British Ecological Society 11 1 399 401 doi 10 2307 2402029 JSTOR 2402029 Lind Owen T 1979 Handbook of Common Methods in Limnology St Louis C V Mosby Co Cole Gerald A 1994 Textbook of Limnology 4th ed Prospect Heights Waveland Press Inc Undersea exploration Encyclopaedia Britannica 2008 Retrieved 1 October 2008 via Encyclopaedia Britannica Online Indiana Clean Lakes Program Volunteer Monitoring www indiana edu Retrieved 9 February 2011 Marine Secchi Disk study www secchidisk org Seafarers Secchi Disk Lavender Samantha Beaugrand Gregory Outram Nicholas Barlow Nigel Crotty David Evans Jake Kirby Richard 2017 Seafarer citizen scientist ocean transparency data as a resource for phytoplankton and climate research PLOS ONE 12 12 e0186092 Bibcode 2017PLoSO 1286092S doi 10 1371 journal pone 0186092 PMC 5718423 PMID 29211734 Schiermeier Quirin 2010 Ocean greenery under warming stress Nature doi 10 1038 news 2010 379 Boyce Daniel G Lewis Marlon R Worm Boris 2010 Global phytoplankton decline over the past century Nature 466 7306 591 596 Bibcode 2010Natur 466 591B doi 10 1038 nature09268 PMID 20671703 S2CID 2413382 Further reading editBrewin Robert J W Pitarch Jaime Dall Olmo Giorgio van der Woerd Hendrik J Lin Junfang Sun Xuerong Tilstone Gavin H 2023 03 07 Evaluating historic and modern optical techniques for monitoring phytoplankton biomass in the Atlantic Ocean Frontiers in Marine Science Frontiers Media SA 10 doi 10 3389 fmars 2023 1111416 hdl 10871 132642 ISSN 2296 7745 Hou Weilin Lee Zhongping Weidemann Alan D 2007 Why does the Secchi disk disappear An imaging perspective Optics Express The Optical Society 15 6 2791 3502 doi 10 1364 oe 15 002791 ISSN 1094 4087 PMID 19532517 Lee ZhongPing Shang Shaoling Hu Chuanmin Du Keping Weidemann Alan Hou Weilin Lin Junfang Lin Gong 2015 Secchi disk depth A new theory and mechanistic model for underwater visibility Remote Sensing of Environment Elsevier BV 169 139 149 doi 10 1016 j rse 2015 08 002 ISSN 0034 4257 OCLC 5867529207 Preisendorfer Rudolph W 1986 Secchi disk science Visual optics of natural waters1 Limnology and Oceanography Wiley 31 5 909 926 doi 10 4319 lo 1986 31 5 0909 ISSN 0024 3590 OCLC 5718371060 Wernand M R 2010 04 27 On the history of the Secchi disc Journal of the European Optical Society Rapid Publications European Optical Society 5 doi 10 2971 jeos 2010 10013s ISSN 1990 2573 External links editSecchi disk at Encyclopedia of Earth Secchi Disk Transparency EPA OWOW Secchi disk simulator The Secchi Disk at The Secchi Dip In Secchi App The global scientific experiment by seafarers to study the marine phytoplankton Retrieved from https en wikipedia org w index php title Secchi disk amp oldid 1197267690, wikipedia, wiki, book, books, library,
