Description: Thalli to 4 m or so long, repeatedly and alternately branched becoming bushy. Upper branches narrow, stalked air bladders in clusters 2 - 6 mm in size in leaf-like branch axils.

Habitat: Epilithic from intertidal rock pools to 10 m deep.

Distribution: First recorded from the Isle of Wight in 1973, has now spread along the south coast of England and to the Channel Islands. In Ireland it has been confirmed from Cos Down, Cork, Kerry and Wexford. Drift material has been found in Co. Sligo. Current data suggests that at least 5 independent events of introduction have occurred. Europe: Mediterranean, Portugal, Spain, France, Netherlands to Scandinavia. Further afield: Japan, introduced to the Pacific coast of North America about 1945 and has since spread from British Columbia to California.

Key Identification Features:

• Small stalked air bladders 2 - 6 mm in size.

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

iNaturalist: Sargassum muticum at iNaturalist World Species Observations database.

WoRMS: Sargassum muticum at World Register of Marine Species. Accepted name: Sargassum muticum (Yendo) Fensholt, 1955. AphiaID: 494791.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Fucales; Sargassaceae; Sargassum