Description: Thallus cylindrical, erect, the cortication at the nodes is distinct to the naked eye. Loosely attached thalli to 20 cms long.

Habitat: Uncommon. Epiphytic, growing on muddy sand. Low littoral to 3 m.

Distribution: Widely dispersed in the British Isles. Europe: Mediterranean, Azores, Portugal, Atlantic coasts of Spain and France, Baltic Sea, Netherlands, Faroes and Norway. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Long Island, New Jersey, Delaware, Maryland, Virginia and Florida. Further afield: Bermuda, Bahamas, West Indies, Jamica and Canary Islands.

Similar Species: Other Ceramium species which are not with spines but with ecorticate internodes.

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

iNaturalist: Ceramium diaphanum at iNaturalist World Species Observations database.

WoRMS: Ceramium diaphanum at World Register of Marine Species. Accepted name: Ceramium diaphanum (Lightfoot) Roth, 1806. AphiaID: 144546.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Ceramiaceae; Ceramioideae; Ceramieae; Ceramium