Phylum: Charophyta   Family: Desmidiaceae

Staurastrum bieneanum L. Rabenhorst 1862

Coesel & Meesters (2013: 71) comment that the original concept of this species is rather unclear and have therefore based their present concept on West & West (1912: 135) exclusive of var. ellipticum Wille. A triradiate taxon, which is as broad as long in face view.
Cell dimensions: L: 25-37 µm; B: 26-38 µm; Is: 8-10 µm.
Zygospore: minus projections: c.33 µm; overall: c.50 µm.
Found in circumneutral, mesotrophic, waters such as moorland bogs and vegetated loch-margins. Frequently found.

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.
West, W. & West, G.S. (1912). A Monograph of the British Desmidiaceae, Volume 4.