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The Seckey Project

Secci disks have been used in fisheries for many years.

From the side of a boat, a disk is lowered into the pond water on a cord and the depth at which it disappears is recorded. The more algae, color, turbidity, etc., the less the distance to such disappearance.

A small device for the angler's tackle box is proposed (with publication). An elaborate device for the staff is proposed since the measures are gross and highly variable.

Idea: suspend a mirror below the water on a 6-foot metal tape measure. Cast a hand-held laser light to the mirror and read the magnitude of the reflection. Correlate with standard Secci readings.

Or, similarly use a flashlight with a controlled light intensity (quick field calibration with changing battery power)

Or (and in addition) cast the laser light at a sharp angle through the surface layer of the water, say over 6-8 feet to a depth of 3-4 feet to get the photosynthetically active surface measure. Correlate this reading with other factors such as fish food productivity, filtered biomass, etc.

See comments of light loss in marine waters.

Biological and Chemical Measurements Within Water

To relate the physiological activity of microorganisms in water to water chemistry, standards were set in Great Britain about 1900 for the dilution of sewage wastes in water. The Biochemical Oxygen Demand (BOD) test is an arbitrary measure of oxygen uptake by the water sample, in-cluding organisms over a 5-day period at 200 degrees C. The BOD test indicates the amount of oxygen necessary for aerobic decomposition of organic matter under standard conditions. The test is a satisfactory measure of the polluting power of organic effluents when the water is warm enough for effective biological activity, and it is the major criterion used in river pollution control.

Chemical Oxygen Demand (COD) also measures the polluting strength of wastes. It is especially important in studying industrial waste effluents. The organic compounds are oxidized to carbon dioxide and water by strong oxidizing agents such as potassium dichromate under acid conditions over a 3-hour period.

Direct-dissolved-oxygen tests can also be made from field-collected water samples. However, the measurements vary greatly depending upon the time of day, the nature and amount of plankton, light, temperature, and other rapidly changing variables.

Turbidity (the amount of particulate matter in the water) can be estimated with a Secchi disk This black-and-white disk is towered into the water and the distance in feet below the surface at which it disappears is a relative measure of turbidity. Readings may vary from person to person and with the time of day and sky conditions. A turbidimeter, which measures the amount of light reflected from the particulate matter in the water, gives quite consistent readings after calibration in Jackson turbidity units.

The measurement of major nutrients such as phosphorus and nitrogen compounds in natural waters, although complex, is important. These nutrients can accelerate eutrophication (over enrichment) and often are added to natural waters from sewage, agricultural runoff, and some industrial wastes. Tests for other specific pollutants like iron and chlorides as well as radionuclides and their biological cycling may also be routinely studied. General tests for pH, detergents, total hardness, total dissolved solids, and organic sludge may also be run (American Public Health Association, 1969).

With the information obtained from these tests, correlations between water chemistry and the aquatic organisms present will indicate water quality. Adequate control methods can then be formulated to provide clean, productive waters.

References

American Public Health Association, Inc., Standard Methods for the Examination of Water and Wastewater, 1969

Butcher, R. W., Studies in the ecology of rivers II. The microflora of rivers with special reference to the algae on the river bed. Ann. Dot., 1969. 46, 813.

Butcher, R. W., Studies in the ecology of rivers IV. Observations of the growth and distribution of sessile algae in the river hull, Yorkshire, Ecology, 1940, 28, 210.

Field Enterprises Educational Corporation, Sci-ence Yearbook, 1971. 106. Foerster, 3. W., and Schlichting, H. E., Jr., Phycoperiphytori in an oligotrophic lake, Trans. Amer.Microscop. Soc., 1965, 84, 485.

Fremling, C. R. 1968. An experiment in diffusion, water pollution and bioassay using polyethylene film as a semipermeable membrane, Amer. Biol. Teacher, 1968, 30, 575.

Mackenthun, K. M., and Ingram, W. M., Biological Associated Problems in Freshwater Environments, U. S. Government Printing Office, Washington, D. C., 1967.

Mackenthun, K. M., The Practice of Water Pollution Biology, U. S. Government Printing Of-fice, Washington, D. C., 1969.

Palmer, C. M., Algae in water supplies, Public Health Service Publication No. 657, U. S. Gov-ernment Printing Office, Washington, D. C., 1959.

Wetzel, R. G., Techniques and problems of pri-mary productivity measurements in higher aquatic plants and periphyton. in Primary Productivity in Aquatic Environments, (G. R. Goldman, editor), University of California Press, Berkeley, 1966.

Wickipedia article, September, 2009 http://www.eoearth.org/article/Secchi_disk

References

American Public Health Association, Inc., Standard Methods for the Examination of Water and Wastewater, 1969.

Butcher, R.W., Studies in the ecology of rivers II. The microflora of rivers with special reference to the algae on the river bed. Ann. Dot., 1969. 46, 813.

Butcher, R.W., Studies in the ecology of rivers IV. Observations of the growth and distribution of sessile algae in the river hull, Yorkshire, Ecology, 1940, 28, 210.

Field Enterprises Education Corporation, Science Yearbook, 1971. 106. Foerster, 3.W., and H.E. Schlichting, Jr., Phyco-periphytori in an oligotrophic lake, Trans. American Microscop. Society, 1965, 84, 485.

Fremling, C.R. 1968. An experiment in diffusion, water pollution and bioassay using polyethylene film as a semipermeable membrane, Amer. Biol. Teacher, 1968, 30, 375.

Mackenthun, K.M., and Ingram, W.M., Biological Associated Problems in Freshwater Environments, U.S. Government Printing Office, Washington, D.C., 1967.

Mackenthun, K.M., The Practice of Water Pollution Biology, U.S. Government Printing Office, Washington, D.C., 1969.

Palmer, C.M., Algae in water supplies, Public Health Service Publication No. 657, U.S. Government Printing Office, Washington, D.C., 1959.

Wetzel, R.G., Techniques of primary productivity measurements in higher aquatic plants and periphyton in Primary Productivity in Aquatic Environments, (G.R. Goldman, editor), University of California Press, Berkeley, 1966.

Wikipedia article, September, 2009 http://www.eoearth.org/article/Secchi_disk

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