found: Work cat.: Betz, C.R. Wisconsin citizen lake monitoring training manual, 2005- :p. 1 (Secchi disc: an 8-inch diameter plate with alternating quadrants painted black and white that is used to measure water clarity) p. 2 (A Secchi disc is an 8-inch black and white disc that is lowered into the water on a marked rope until it can no longer be seen. The disc is then raised until you can just see it again and the average depth is recorded)
found: Preisendorfer, R.W. Eyeball optics of natural waters : Secchi disk science, 1986.
found: Chemistry, temperature, and Secchi disc data for Hatchery Bay, western Lake Erie, 1996.
found: Fuller, L.M. Predicting water quality by relating secchi-disk transparency and chlorophyll a measurements to satellite imagery for Michigan inland lakes, August 2002, 2004.
found: Wikipedia, May 16, 2007(Secchi disk. Created in 1865 by Pietro Angelo Secchi, the Secchi disk is a device used to measure water transparency in open waters of lakes, bays, and the ocean.)
