Algoflora of lakes in the Kurgal’sky Nature reserve (Leningrad region)

Various algocenosises in the brackish Lake Lipovskoe and ultra-oligotrophic Lake Beloe located in the Kurgal’sky Nature reserve were studied in May and July of 2019. In the algal flora of the lakes studied, we found 291 taxa belonging to 9 orders. The both lakes were characterized by high species richness, namely: 179 and 181 algae taxa were identified in the Lake Lipovskoe and Lake Beloe, respectively. In the Lake Lipovskoe, its phytoplankton was dominated by Cyanophyta, Cryptophyta and Dinophyta, among which brackish-water and marine species were presented. In the periphyton of this Lake, brackish-water diatoms and green algae were the most abundant. In the Lake Beloe, its phytoplankton was dominated by Dinophyta, Bacillariophyta and Chlorophyta; the blue-greens, diatoms and green algae dominated in the periphyton of Lake Beloe. Despite that the lakes are located close to each other, their algal flora is quite different: the Sorensen similarity index between the two lakes was 38% only. The phytoplankton biomass in both lakes was low, increasing from spring to summer. In the Lake Lipovskoe, the phytoplankton biomass varied from 0.45 to 1.9 mg/L, chlorophyll a fluctuated from 3.9 to 7.1 µg/L. In the Lake Beloe, the phytoplankton biomass varied from 0.3 to 1.4 mg/L, chlorophyll a fluctuated from 0.45 to 1.3 µg/L. The periphyton biomass was 20 g/m2  (chlorophyll a being 22 mg/m2 ) and 17 g/m2 (chlorophyll a being 17 mg/m2 ) in the Lake Lipovskoe and Lake Beloe, respectively. Nowadays, the ecological status of both lakes can be considered satisfactory, because based on trophic conditions and species compositions they belong to waterbodies of clean and satisfactory clean conditions (II–III classes of water quality). To preserve the unique flora of the lakes in the Kurgal’sky Nature reserve, nature-protected measures should be strengthened.