The first find of Althenia filiformis (Zannichelliaceae) in the Omsk region

The genus Althenia Petit ( Zannichelliaceae ) is new to the flora of the Omsk Region. In 2016, in two salt lakes in the far west of the West Barabinsk Plain, populations of Althenia filiformis F. Petit subsp. orientalis Tzvel were found. In the studied habitats, the projective cover degree of A. filiformis was within 1 %, the height of the generative shoots reached 4 to 5 cm. A flowering hydrophyte Ruppia maritima L. also contributed to the formation of the coenoses, although the green algae Ulothrix implexa (Kütz.) Kütz., U. flacca (Dillw.) Thurn. and cyanobacteria of the genus Oscillatoria Vauch. prevailed. Such aggregations were common in vast water spaces along the shore line of both lakes. In the West Siberian Plain, Althenia filiformis subsp. orientalis occurs in sodium chloride and sulphate sodium chloride waters with salinity between 18,1 to 79,97 g/dm3, total hardness between 98,9 to 420,5 meq/dm3, рН between 7,1 to 9,2 or higher. A study of the morphology and ecology of A. filiformis showed that in the south of the West Siberian Plain this species was a typical therophyte. As for water salinity, A. filiformis together with Ruppia drepanensis L. and R. maritima forms a salt-water floristic complex of species which does not extend into fresh waters.