Description: This species can have a variable appearance. It commonly forms tufts up to 10 cm tall of erect branches surrounding a central axis. Under a hand lens you should be able to see a 'diving ladder' pattern formed by the pigment in some cells/parts of cells, which otherwise appear clear. It is brown to red, but bleaches to a yellow colour. Some parts may appear transparent. The holdfast is disc-shaped, but may also be formed by downward growing filaments if growing as an epiphyte.

Habitat: In rockpools and shallow subtidal. Grows as an epiphyte on other algae, and sometimes also on other artificial material.

Distribution: Most commonly recorded in southern areas but there are records from all around Britain and Ireland.

Similar Species: This species should be able to be identified in the field using a hand lens.

Key Identification Features:

• Tufts up to 10 cm.
• 'Diving ladder' pattern visible using a hand lens.
• Brown to red, some sections may be transparent. Disc-shaped holdfast.
• Holdfast is formed from downward facing filaments when epiphytic.

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

iNaturalist: Melanothamnus harveyi at iNaturalist World Species Observations database.

GBIF data for Melanothamnus harveyi

WoRMS: Melanothamnus harveyi at World Register of Marine Species. Accepted name: Melanothamnus harveyi (Bailey) Díaz-Tapia & Maggs, 2017. AphiaID: 1027787.

Classification: Biota; Plantae; Biliphyta; Rhodophyta; Eurhodophytina; Florideophyceae; Rhodymeniophycidae; Ceramiales; Rhodomelaceae; Streblocladieae; Melanothamnus