Distribution of Lemna at the Range Boundary in the North-West of the Murmansk Region as a Result of Anthropogenic Changes in Water Bodies

Data on the new localities of Lemna minor, L. trisulca, and hybrid between L. minor and L. turionifera (L. × japonica) (Lemnaceae) in the north-west of the Murmansk region (north of 68.5° N), i.e., in the Pasvik State Nature Reserve and neighboring territories in the drainage basin of the Paz River, are presented. Lemna minor and L. trisulca were previously known for the region by several reports. In the north-west of the Murmansk region, two new localities of Lemna minor, one locality of L. × japonica, and ten localities of L. trisulca were found. In total, representatives of Lemna occurred in 18 studied sites: L. minor in two, L. × japonica in two, and L. trisulca in 16 (L. minor and L. trisulca grew together in two sites). In the studied rivers and lakes, the pH range of water varied from 6.0 to 7.6, i.e., was mainly neutral (the average value was 6.9). TDS varied in the range from 17 to 251 ppm (on average, 53 ppm). The localities of L. minor in the unnamed lake near Zapolyarnyi town and in Kuetsjarvi Lake are probably the northernmost in the world, while the locality of L. trisulca in the Paz River in Klistervatn Lake is the northernmost in European Russia. In the north of the Murmansk oblast, L. minor and L. × japonica were associated only with anthropogenic eutrophicated water bodies with increased water mineralization in comparison to the background value. These taxa can be considered as indicators of high trophicity in this region. The localities of L. trisulca are mainly anthropogenic transformed water bodies. The maximum abundance of this species is also recorded in the areas of increased trophic level.