Phylum: Charophyta   Family: Desmidiaceae

Staurastrum lapponicum (Schmidle) Grönblad

An acidophile rather common in the phytoplankton

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition) The Freshwater Algal Flora of the British Isles
John, D.M. & Williamson, D.B. (2009) A Practical Guide to the Desmids of the West of Ireland