Description: Thallus a broad flat membrane, two cells thick, growing from a small holdfast to 50 cms or more long. The blade is often deeply devided with microscopic teeth near the base.

Habitat: Epilithic or epiphytic in the sublittoral, also in brackish water.

Distribution: Widespread in the British Isles from the Shetland Islands to the Channel Islands, probably under-recorded. Europe: Mediterranean, Portugal, Atlantic coasts of Spain and France, Netherlands, Baltic Sea, Norway, Faroes and Iceland. Atlantic coast of North America: Canada, Connecticut and Long Island, Delaware, Maryland and Virginia. Further afield: Canary Islands, Jamaica, and in the Pacific from Alaska to California, Chile, South Africa, Australia and New Zealand.

Similar Species: Ulva lactuca and Umbraulva olivascens, Ulva rigida has microscopic teeth near the base of the frond.

Key Identification Features:

• Microscopic teeth near the base of the frond.

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

iNaturalist: Ulva rigida at iNaturalist World Species Observations database.

WoRMS: Ulva rigida at World Register of Marine Species.