Phylum: Cyanobacteria   Family: Nostocaceae

Trichormus variabilis (Kützing ex Bornet & Flahault) Komárek & Anagnostidis, 1989

A common species that can be found in freshwater as well as marine

References: 
John, D.M., Whitton, B.A. & Brook, A.J. (2011) - The Freshwater Algal Flora of the British Isles