Whiting Events

(Source: Environmental Assistance and Surface Water Quality Divisions, Michigan Department of Environmental Quality, 800-662-9278)

Whiting event on Black Lake, Cheboygan County, July 2005

In some lakes, a naturally-occurring phenomenon makes the color of the water change from clear blue to gray or milky white. This phenomenon is often the result of natural processes, not environmental pollution.

The cause for this whiting phenomenon is the precipitation (coming our of the water as a solid) of calcium carbonate. Calcium carbonate is a white, crystalline mineral that is widely distributed in nature and is the main ingredient in limestone, marble, coral, calcite, and chalk. Whiting events occur in lakes with very high concentrations of calcium carbonate (hard water lakes) during early summer. As the calcium carbonate precipitates, it forms chalky white clouds underwater and rains calcium carbonate on the lake bottom. When the calcium carbonate particles consolidate on the lake bottom, they form a soft rock called marl.

In the summers of 1998 and 1999, NASA's satellite capture images of a mysterious flush of color that spread across Lake Michigan . The color change was attributed to either a whiting event or an algae bloom.

Some white material in water can indicate pollution. When deciding if the milky appearance is natural or caused by pollution, consider the following:

Proximity to a potential pollution source
Some industries such as mining, metal cutting, salt processing, and paper manufacturing have materials that can cause water to appear milkly when released into the environment. A defined waste stream into the lake could indicate a pollutant source, while a sudden change of color from within the lake may indicate a whiting event.

The time of year
Whiting events most often occur in early to mid-summer.

A simple field test
Gather white particles by filtering some of the lake water through a fine filter. Next, place a drop of vinegar on the filtered white particles Bubbling or fizzing will occur in the presence of calcium carbonate. This is the same reaction that would occur if you put vinegar on baking soda.

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