Description: Forming tangled masses of branched uniseriate filaments.

Habitat: Abundant. Upper littoral especially in areas of low salinity.

Distribution: Widespread around the British Isles from the Shetlands to the Channel Islands. Europe: Portugal, Spain, France, Netherlands, the Baltic, Norway, Faroes, Jan Mayen and Bjornoya and Iceland. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut, New Jersey, Delaware, Maryland and Virginia. Further afield: Arctic Sea from Spitzbergen, Novaya Zemlya, Baffin Island and the west coast of Greenland, Alaska to Chile, South Africa and Japan.

Similar Species: Rhizoclonium tortuosum.

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

iNaturalist: Rhizoclonium riparium at iNaturalist World Species Observations database.

WoRMS: Rhizoclonium riparium at World Register of Marine Species.