What causes that turquoise color in some lakes?
Lakes with this coloration are often referred to as “marl lakes” and usually have very good water quality. Their lakebeds typically consist of marl, a mixture of clay, sand and limestone, which has a soft texture. These lakes also tend to be hard-water lakes, those with higher concentrations of calcium, magnesium and bicarbonate that can bind excess nutrients, such as phosphorus, and limit algal growth. The turquoise color is caused by the backscattering of light from the calcium carbonate floc suspended in the water and the high reflection of the light-colored (nearly white) marl lakebed. This backscattering is predominately blue-green in appearance versus the more green or yellow appearance seen in lakes with more suspended organic materials and sediments.
