Phylum: Charophyta   Family: Desmidiaceae

Staurastrum lapponicum (W. Schmidle) R. Grönblad 1926

Mainly a triradiate species but 4-radiate cells are occasionally encountered. The size of the granules can vary between populations; it lacks supraisthmial granules found in similar species.
Cell dimensions: L: 30-45.3 µm; B: 30-42.9 µm; Is: 8.2-15 µm.
Found in circumneutral waters such as loch-margins, and also ephemeral winter flood plains. Rather common.

References: 
Coesel, P.F.M. & Meesters, K.J. (2013). European Flora of the Desmid Genera Staurastrum and Staurodesmus.
Van Westen, M.C. (2024). Sieralgen in Drenthe.