Description: Erect densely and irregularly branched in tufts of uniseriate filaments to 30 cms long, ecorticate. The plurilocular sporangia so9metimes tapering and ending as a short hair. Variable.

Habitat: Abundant. Epiphytic on other large algae. Mid littoral to sublittoral.

Distribution: Widespread in the world. Common on the coasts of the British Isles. Europe: Mediterranean, Portugal, Atlantic coasts of Spain and France, Denmark, Germany, Baltic Sea, Norway, Sweden, Faroes and Iceland. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Long Island, New Jersey, Delaware, Mayland and Virginia. Further afield: Spitzbergen, Murman Sea, White Sea and Baffin Bay in the Arctic Seas, Canary Islands, Mauritania, Morocco, South Africa, Pacific coast of North America, Argentina, Chile, Japan, China, south coast of Australia.

Similar Species: Many finely branched brown algae are similar. Microscopic examination required for determination.

Key Identification Features:

• Ribbon shaped plastids and plurilocular sporangia sometimes with a short terminal hair.

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

iNaturalist: Ectocarpus siliculosus at iNaturalist World Species Observations database.

WoRMS: Ectocarpus siliculosus at World Register of Marine Species. Accepted name: Ectocarpus siliculosus (Dillwyn) Lyngbye, 1819. AphiaID: 145410.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Fucophycidae; Ectocarpales; Ectocarpaceae; Ectocarpus