Potamogeton praelongus Wulfen 1805 (Potamogetonaceae) as a potential species for inclusion in the Omsk region Red Book

This work is intended to prepare a justification for the inclusion of Potamogeton praelongus in the third edition of the Red Book of the Omsk Region. The tasks include the analysis of the species distribution in the region, summarizing the original quantitative data about its tolerance to a number of aquatic factors in the West Siberian Plain, and clarification of its ecobiomorphological parameters. Over more than 60 years in the Omsk Region, the species was only reported in 5 lakes of the forest and forest-steppe zones, indicating that it is rare. We obtained the quantitative information about the condition of the species population only in 2023 in the lake Bugaly of the Bolsherechensky District. The population has an area of up to 0.28 km2. The species forms a monodominant community with a projective cover of up to 30%. The community is formed on grey and dark-grey thin-detritus silts in the depth range 1.2-3.0 m. According to hydrochemical tests, the water in lake Bugaly has pH = 6.9, total hardness 2.06 mg-eq/dm3, and total salt content 0.44 g/dm3. In the West Siberian Plain, P. praelongus was found in waters with pH between 6.3 to 7.6 with total hardness 0.26-6.40 mg-eq/dm3 and total salt content 0.03-1.10 g/dm3. The content of lead in the ecotopes of the species was 0.10-0.22 µg/dm3, nickel 0.76 µg/dm3, zinc 2.58-17.61 µg/dm3, cadmium 0.01-0.02 µg/dm3, chromium 0.43-0.44 µg/dm3, copper 0.84-5.97 µg/dm3, manganese 7.61-32.55 µg/dm3. The content of the soluble forms of iron was up to 1,585.0 µg/dm3, which suggests that the species is tolerant to iron. Based on the ecobiomorphological study performed, P. praelongus can be characterized as a perennial (vegetatively annual), polycarpous, long-shooted, stoloniferous, emergent-flowering, neutrophilic, typically freshwater, water hardness-indifferent, iron-tolerant, silt hydatophyte. Potamogeton praelongus might be recommended for inclusion in the coming issue of the regional Red Book with status 3(R) as a rare species.