Ulva rigida C. Agardh
Common names: Sea Lettuce. Glasán (Irish).
Description: Thallus sheet-like, emerald green, stiff at the base and more delicate near the growing edges, to 300 long, sometimes with irregular elliptical holes (above). Persists throughout the year.
Habitat: on rock and growing as an epipthyte, often developing "green tides"
Distribution: Common and widely distributed.
Key characteristics: emerald green colour and stiffness of thallus; however, this and other species of Ulva in the NE Atlantic require expert identification, and even then there is much dispute as to the status of the various species that have been reported including U. lactuca, U. gigantea, U. scandinavica, and U. armoricana.
Photographs © M.D. Guiry