Sandimirov S.S. Catalogue of lakes in the Russian, Finnish and Norwegian Border Area. Finland, Jyvaskyla: Kopijyva Oy, 2008.

Fig. 43. Vertical distribution of the concentrations ofNi, Co, Pb and Cd (цд/д, dry weight) in the sediment core of Lake Guokalab­ balat. 2.5.3. Hydrobiological studies H yd rob iologica l in d ices Cyanobacteria are almost completely absent from the phytoplankton communities in Lake Guokalabbalat. The dominant species are the division of yellow-green al­ gae ( Crysophyta ), diatoms ( Bacillariophyta ) and green algae ( Chlorophyta ) (Sharov, 2004). According to earlier studies, the dominant complex in zooplankton communities ofJarfjord lakes is one species of rotifera ( K ellicotia longispina ) (Yakovlev et al., 1991). The density ofCladocerae and Copepoda does not exceed 15 000 specimens/m3. Cope- pods are predominant. The predominant species in the division of benthic communi­ ties are mayfly ( Ephemeroptera ) and stoneflies ( P lecop tera ). The relative abundance (%) of acid- and pollution-sensitive species is 1.6. The value of the Shannon diversity index of the benthos is 3.23 (Yakovlev et al., 2007). Ichthyofauna. Studies on the fish community of Lake Guokalabbalat were conducted in 1995 (Kashulin, 2004). The data indicate that trout and arctic char inhabit the lake. The average length of char is 16.3 cm, and weight 45 g.The size of the larges individu­ als reaches 30.8 cm and 314 g, respectively. The bulk of the char population consists of 2- to 3-year-old fish (~90%). 3-year-old specimens are predominant, and fish of other age classes are occasionally caught. Males are predominant in the sex distribu­ tion (1.3:1). H eavy m etals in £sh Heavy metal (Cu, Ni, Pb, Cd and Hg) concentrations in fish muscle do not exceed the established standard values (Table 29). Nevertheless, the concentrations of Cu (|ig/g dry weight) in the liver of char (up to 217.6 |ig/g) and trout (up to 266.6 |ig/g) are considerably higher than in muscle. The Ni and Cd concentrations in the kidneys of the above fish species reach 5.1 and 5.9 [ig/g in char, and 6.2 and 3.9 |_ig/g in trout, respectively. The variation in the Hg concentrations in this species are not significant. The analysis of heavy metal accumulation in different fish species showed that trout have the highest concentrations of Ni (in kidneys) and Cu (in liver). Lead and Hg ac­ cumulate more strongly in char muscle (Fig. 44). Catalogue o f Lakes in the Russian, Finnish and Norwegian BorderArea 85