Description: This 1 aquatic lichen with thick, foliose, tongue-like lobes (to 1cm wide) can be found growing in loose bundles on rocks and boulders in clean, usually fast-flowing rivers and streams. Though grey when dry, the thallus becomes emerald green when wet which is useful in distinguishing it from other members of the same family. It occurs in the zone just above the ‘submerged’ which means it is usually at, or just above or below, the waterline. It is scattered in suitable habitat in Ireland.

Key Identification Features:

• The emerald green, rounded, foliose thallus when submerged helps to indicate this species. It is beige coloured when dry
• All other aquatic species of Dermatocarpon are relatively unchanged when submerged.

Original text submitted by Simon Davey

Distribution Map from NBN: Dermatocarpon luridum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Dermatocarpon luridum at iNaturalist World Species Observations database.