Phylum: Charophyta   Family: Closteriaceae

Closterium navicula (L.A. De Brébisson) J. Lütkemüller 1905

There is considerable variation in size and shape within this species and may include more than one taxon. Different habitat types may also suggest this.
Cell dimensions: L: 49-80 µm; B: 14-18 µm; L/B: 3.4-4.6.
Found in acidic habitats such as peaty pools and bogs, but also in slightly alkaline waters such as loch-margins. According to West & West (1904: 75) it is widely distributed, particularly in mountainous districts.

References: 
Coesel, P.F.M. & Meesters, K.J. (2023 second edition). Desmids of the Lowlands.
Van Westen, M.C. (2024). Sieralgen in Drenthe.
West, W. & West, G.S. (1904). A Monograph of the British Desmidiaceae, Volume 1.