This site supports a very rich invertebrate and amphibian fauna. A wide range of seminatural habitats are present, including valley mire, open water, swamp and tall fen. These habitats have a restricted distribution in the Mendip Hills. Priddy Pools is situated in the central Mendip lead orefield and the ecology of the area bears the mark of the lead industry. The northern pool was dammed in the 1850s to provide a supply of running water for the sifting and washing of slag. Lead was processed at St Cuthbert's Works until 1908. The hydrology of the site is complex. Nutrient-poor water flows from springs in the north of the site to St Cuthbert's Swallet where it disappears before re-emerging at Wookey Hole. A valley mire has developed in the area immediately to the south of the springs. Sphagnum recurvum and Sphagnum auriculatum are the most frequent mosses, and a range of higher plants can be found. Additional interest lies in the flora that can tolerate high concentrations of lead in the soil such as spring sandwort (Minuartia verna) and the moss Ditrichum plumbicola.