Influence of Alien Species Pistia stratiotes L., 1753 on Representative Species of Genus Salvinia in Ukraine

This work purpose was to find the impact of Pistia stratiotes L., 1753 - a new species on the territory of Ukraine, on the vitality of other free-floating hydrophytes so-called pleuston- Salvinia natans (L.) All., 1785, S. laevigatum (Humb. and Bonpl. ex Willd.) Heine, 1968, to determine the degree of stability and competitiveness of these species for resources in natural ecosystems relatively to the undesirable species. To find out the influence of P. stratiotes on other free-floating on the water surface plant species which compete for elements of nutrition among each other, we have investigated changes in the content of photosynthetic pigments in S. laevigatum and S. natans, which were exhibited with P. stratiotes for 14 days. Besides changes in water indices, oxygen content, mineralization and pH, were measured.