Does tea-colored water in a lake mean it is polluted?
No. The color of water in a lake is not related to bacterial pollution or unsanitary conditions. It is caused primarily by decaying organic matter such as leaves, bark, humus and aquatic plants. Metals such as iron and manganese that occur naturally in the soils of the watershed and lake sediments may also contribute to a lake’s color. Highly colored lakes frequently have extensive wetlands along their shores or within their watersheds. It is the decomposition of the organic matter produced in these wetlands that contributes to the color. These highly colored ponds are usually naturally acidic because the dissolved organic matter causing the color is primarily organic acids such a humic and fulvic acids. Color is often associated with shallow lakes with mucky lake bottoms, primarily because lakes receiving such organic debris tend to have filled in over geologic time. Large, deep lakes with sandy/rocky bottoms tend to have clear waters.
