Phylum: Charophyta   Family: Closteriaceae

Closterium rostratum J. Ralfs 1848

There is some similarity with Closterium kuetzingii but that species is more slender. The fine striae average 10/10 µm.
Cell dimensions: L: 291-420 µm; B: 17-28 µm; Ap: 3-4 µm; L/B: 12-21.
Widespread but infrequently recorded in the Outer Hebrides. Generally, an acidophile of boggy pools and vegetated loch-margins, but tolerant of less acidic conditions. Also found with mosses.

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.
Ralfs, J. (1848). The British Desmidieae.
Van Westen, M. (2024). Sieralgen in Drenthe.