Dystrophic lake

Dystrophic lake in Bielawa nature reserve in Poland

Dystrophic lake refers to lakes with brown- or tea-coloured waters, the colour being the result of high concentrations of humic substances and organic acids suspended in the water. Because the term has long been misused in the literature, these lakes are better referred to as humic lakes. Although dystrophic lakes are often considered acidic, and nutrient-poor (oligotrophic), these lakes actually vary greatly in terms of both pH and productivity. They are common in the taiga of North America and Eurasia.

An example of this type of lake is Humic Lake in South Georgia, named for the dark water caused by the leaching of decaying peat from nearby slopes.