Phylum: Charophyta   Family: Desmidiaceae

Closterium leibleinii J. Ralfs 1848

A robust species with noticeable tumidity and an arc in the region of 140 degrees. It’s worth comparing with Cl. tumidulum F. Gay 1884 although that species tends to be smaller, but the parameters overlap.
Cell dimensions (2) L: 147-155 µm; B: 20.1-21.3 µm; Ap: 2.7-3.1 µm; Arc: 140-148°; L/B: 7-8.
A species that prefers circumneutral to slightly alkaline waters, although it has been found in more acidic habitats in Europe. In the Outer Hebrides it is found in shallow loch-margins but rarely recorded.

References: 
Brook, A.J. & Williamson, D.B. (2010). A Monograph on some British Desmids.
Coesel, P.F.M. & Meesters, K.J. (2023 second edition) Desmids of the Lowlands.