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The Secchi Dip-In |
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Contact the Dip-In at:
Web Site Updated: May 05, 2008 |
What is a Secchi Disk?  A Secchi disk is an 8-inch (20
cm) disk with alternating black and white quadrants. It is lowered into
the water of a lake until it can be no longer seen by the observer. This
depth of disappearance, called the Secchi depth, is a measure of the transparency
of the water. The Secchi disk measures the transparency of the water.
Transparency can be affected by the color of the water, algae, and
suspended sediments. Transparency decreases as color, suspended
sediments, or algal abundance increases. Water is often stained yellow
or brown by decaying plant matter. In bogs and some lakes the brown
stain can make the water the color of strong tea. Algae are small, green
aquatic plants whose abundance is related to the amount of plant
nutrients, especially phosphorus and nitrogen. Transparency can
therefore be affected by the amount of plant nutrients coming into the
lake from sources such as sewage treatment plants, septic tanks, and
lawn and agricultural fertilizer. Suspended sediments often come from
sources such as resuspension from the lake bottom, construction sites,
agricultural fields, and urban storm runoff. Transparency is an indicator of the impact of human activity on the land surrounding the lake. If transparency is measured through the season and from year to year, trends in transparency may be observed. Transparency can serve as an early-warning that activities on the land are having an effect on a lake. Return to the Secchi Disk Page
For more information on the Great American Secchi Dip-In, contact us at: DipIn@kent.edu or write The Secchi Dip-InDepartment of Biological Sciences Kent State University Kent OH 44242 |