Phylum: Cyanobacteria   Family: Gloeotrichiaceae

Gloeotrichia pisum Thuret ex Bornet & Flahault

Spherical colonies found on submerged plants and stems in freshwater

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