Total Salt Content and Chemical Composition of Water as Important Factors for the Study of Ecobiomorphes and Ecological Niches of Hydromacrophytes

The aim of the work is to substantiate approaches to the differentiation of ecobiomorphes of hydromacrophytes based on quantitative data on halotolerance. The study of ecobiomorphes and ecological niches of hydromacrophytes is an important problem of hydrobotany. Most of the existing systems of the life-forms of aquatic macrophytes do not contain any quantitative information on the relation of these plants to the abiotic factors of the aquatic environment. Total salt content along with total hardness and pH of water are important factors strongly affecting the aquatic plants. Quantitative ranges of these factors revealed upon laboratory tests of water samples from natural ecotopes along with their biological-morphological parameters form the basis for the differentiation of the ecobiomorphes and the ecological niches of each species. It was demonstrated that in continental water bodies, quantitative information on salt content and composition of water can only be obtained based on laboratory tests. Based on studies conducted in 19842023, quantitative ranges for water salt content for 247 species of hydromacrophytes in the West Siberian Plain were obtained. In the aquatic marcophyte flora of this region, 2 floristic systems were identified: a freshwater one and a saltwater one. The natural ecological threshold between these systems is the salt content range of 8-25 g/dm3, which is called critical salt content in hydrobiology. Species of a freshwater system limited within a salt content of up to 0.2 g/dm3 are called ultrafreshwater, up to 1 g/dm3 typical freshwater, up to 3 g/dm3 conditionally freshwater, up to 5 g/dm3 slightly saltish freshwater, up to 8 g/dm3 middle-saltish freshwater, up to 25 g/dm3 strongly saltish freshwater. Species living in a salt content range between 8 to 80 g/dm3 form a saltwater system. These grades are used to identify ecobiomorphes of hydromacrophytes in combination with other ecological parameters (concentration of main ions and soluble forms of certain metals, total hardness and pH of water). These borders divide the ecological niches of the species making it possible to predict potential composition of hydrophyte conenoses based on the information on water salt content and composition in specific water bodies.