Description: Very small branching uniseriate filaments, erect axes less than 1 mm tall with few branches.

Habitat: Epiphytic on other algae, low and sublittoral to 5 m.

Distribution: Widely distributed around the British Isles. Europe: Mediterranean, Atlantic coast of Spain and France, Baltic Sea, Norway, Faroes, Spitzbergen and Iceland. Greenland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut. Further afield: the Canary Islands, West Indies, Alaska to Vancouver Island, British Columbia, California and Australia.

Similar Species: All species of Acrochaetium are similar and require microscopic examination for identification.

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

iNaturalist: Acrochaetium microscopicum at iNaturalist World Species Observations database.

WoRMS: Acrochaetium microscopicum at World Register of Marine Species.