Description: Main axis with transverse and longitudinal divisions ending with a large apical cell.Thalluserect 5 to 10 cms long, naked towards the base, the final branches opposite (pinnate) at every joint and closely set. Feather-like.

Habitat: Not uncommon. Sublittoral epilithic.

Distribution: Widely distributed around the British Isles. Europe: Baltic Sea, Norway, Faroes and Iceland. Atlantic coast of North America: Canada, Maine and New Hampshire. Further afield: Arctic Seas from Spitzbergen, Murman Sea, White Sea, Novaya Zemlya, Siberian Sea, American Arctic Sea Cumberland Sound and west coast of Greenland in Baffin Bay.

Similar Species: Most species of Sphacelaria, and other small branched brown algae, are very alike and require microscopic examination for identification.

Key Identification Features:

• Feather-like with opposite branching.

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

iNaturalist: Sphacelaria plumosa at iNaturalist World Species Observations database.

WoRMS: Sphacelaria plumosa at World Register of Marine Species. Accepted name: Chaetopteris plumosa (Lyngbye) Kützing, 1843. AphiaID: 497297.

Classification: Biota; Chromista; Harosa; Heterokonta; Ochrophyta; Phaeophyceae; Dictyotophycidae; Sphacelariales; Sphacelariaceae; Sphacelaria