Soils having at least 18 inches of organic matter at the soil surface are called hydric organic soils. These organic soils often are black, dark brown, or dark gray in color. Because their soils are acidic, bogs have even slower decomposition than most other wetlands. In bogs the moss and other organic matter hardly break down at all. A very thick layer of peat forms.
Peat soils are often a dark brown color.
Organic soils also may have a rotten egg smell. Since there is little or no oxygen in the soil, the ordinary bacteria that break down the organic matter cannot live. However, not all bacteria need oxygen to survive. In wetlands with organic soil you will find anaerobic bacteria. Anaerobic means that they do not need oxygen to live.