Description: Thallus up to 1 m long, bushy, attached by conical disc holdfast. Axis cylindrical, branches arising spirally. Deciduous, leaving prominent scars or stumps. Aerocysts ovoid and up to 5 mm long in the terminal regions of the ramuli. Strongly iridescent underwater.

Habitat: Not uncommon. Epilithic. Rock pools of the low littoral and upper sublittoral.

Distribution: A south-western species, all around Ireland but generally from the south-weste, south-west Wales, south-west England and west Scotland. Europe: western Mediterranean (coast of north Africa), Azores, Atlantic coasts of Spain and France. Further afield: Canary Islands, Mauritania and Cape Verde Islands.

Similar Species: Other species of the genus Cystoseira.

Key Identification Features:

• Strongly iridescent underwater.

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

iNaturalist: Cystoseira tamariscifolia at iNaturalist World Species Observations database.

WoRMS: Cystoseira tamariscifolia at World Register of Marine Species.