temperature | depth | salinity | dissolved oxygen | turbidity | pH | nutrients | chlorophyll

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Turbidity is measured at many NERRS sites using an electronic monitor. Another way to measure turbidity is to lower a device called a Secci (pronounced seh-key) Disc into the water. A Secci Disc has black-and-white elements. As the disc is lowered into the water, increasing turbidity will cause the black-and-white areas to fade into one another, and the disc will slowly disappear from sight. To determine the turbidity of the water, a mathematical calculation is performed based on the depth of water at which the Secci Disc “disappeared.”

Turbidity is essentially a measurement of how cloudy or clear the water is, or, in other words, how easily light can be transmitted through it. As sediments and other suspended solids increase in the water, the amount of light that can pass through the water decreases. Thus, the cloudier the water, the greater the turbidity. As algae, sediments, or solid wastes increase in the water, so does turbidity.

Turbidity affects organisms that are directly dependent on light, like aquatic plants, because it limits their ability to carry out photosynthesis. This, in turn, affects other organisms that depend on these plants for food and oxygen.

Scientists often consider turbidity of the water in connection with other factors to get a better understanding of its causes and consequences. For example, high levels of turbidity can identify problems with shoreline erosion, or sewage processing facilities not functioning properly.


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