Phylum: Charophyta   Family: Closteriaceae

Closterium limneticum var. tenue E. Lemmermann 1899

This taxon differs from the nominate variety and var. fallax in being noticeably less broad. Cells of Cl. limneticum varieties are noted for the chloroplast reaching a long way towards the apices and the terminal vacuoles supporting a single large crystal. Cl. aciculare is similar but can be separated by the chloroplast not reaching so far to the apices and that taxon supports a group of small crystals near the ends of the chloroplast.
Van Westen’s cell dimensions: L: 78-300 µm; B: 2.7-5.0 µm; L/B: 23-70
Mine - single cell dimensions: L: 256 µm; B: 3.4 µm; L/B: 75.
A seemingly rare species in the Outer Hebrides but may have been overlooked or misidentified in the past. Found in circumneutral waters.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe.