Phylum: Charophyta   Family: Desmidiaceae

Cosmarium sp. Charnain and near Lochmaddy 

This unidentified species has some affinity with Cosmarium tinctum in terms of size, general shape, and the cell wall being generally coloured yellowish- to reddish-brown due to incrustation with iron salts. It differs in having a closed sinus from the isthmus and, for the most part, distinctly retuse apices. Two populations have now been found which are remarkably consistent in size, shape and colour.
Cell dimensions: L: 12.1-13.7 µm; B: 11.1-12.7 µm; Is: 5.3-5.9 µm; Th: 6.7-7.7 µm; L/B: 1.06-1.15.
The habitat is acidic moorland bogs and pools, especially with Sphagnum.

References: 
Kouwets, F.A.C. (2025). European Flora of the Desmid Genus Cosmarium.