Vandysh O. Assessment of copper-nickel industry impact on a subarctic lake ecosystem. The Science of the Total Environment. 2003, T. 306, № 1-3, c. 78-83

A. Lukin et al. / The Science o f the Total Environment 306 (2003) 73-83 77 Fig. 3. Phytoplankton volume (mm3 m 3). *, Cu-465 and 1499 mg g \ Co-81 and 165 *, Zn-162 and 309 mg g 1, Cd-0.33 and (Kryuchkov and Makarova, 1989) and the consid­ erably increased heavy metal concentrations at a sediment depth of 6 cm may be related to this period (Fig. 2 ). Therefore, the calculated sedimen­ tation rate is estimated at approximately 3-mm yeary \ Concentrations of Ni in the surface sediment layer of 12 cores were between 1556 and 3073 mg g mg g 3.40 mg g _1, Pb-11 and 52 mg g _1, Hg-0.31 and 0.42 mg g 1. Mean concentrations and contami­ nation factors are given in Table 1. The highest concentrations were recorded in the deepest site (station 3, 32 m depth) and in the area close to the mouth of the Kolosjoki river carrying the bulk of waste effluent from Pechenganickel (stations 4 and 5). Surface sediments of Lake Kuetsjarvi have higher concentrations of Ni, Cu, Hg and Co (Table 1, Fig. 2) as compared with the average back­ ground values in the Kola Peninsula (Dauvalter, 1997). Other heavy metals (Zn, Pb and Cd) did not differ significantly from the background values. 3.2. Phytoplankton Phytoplankton was found to comprise 83 spe­ cies, forms and varieties: Chrysophyceae-15, Chlo- rophyceae-28, Conjugatophyceae-1, Cryptophy- ceae-5, Cyanophyceae-7, Diatomophyceae-23, Dinophyceae -4. Maximum phytoplankton amounts (17335-mm3 my3) were recorded in the second 10 days of July 1993 in the central part of Lake Kuetsjarvi. During the investigations, the average total vol­ ume of plankton algae was low—623 mm3 m 3 in August 1994 and 1889 mm3 m 3 in July 1996 (Fig. 3). The diatoms Aulacoseira varians and Synedra spp. dominated the southern part of the lake in 1994. At that time Chlorophyceaen Pan- dorina morum dominated the northern part. Dia­ toms Asterionella formosa and Diatoma elongatum dominated both the northern part and the outlet. A few other groups of phytoplankton dominated the northern part of the lake in July 1996: Chryso- chromulina sp., Dinobryon sociale among Chry- sophyceae, Eudorina sp . among Chlorophyceae, Asterionella formosa among Diatoms. 3.3. Zooplankton A total of 11 Rotatoria, 6 Cladocera and 6 Copepoda species were observed in the investigat­ ed period. The highest numbers of species were recorded in 1993 and 1994. The dominant species in Lake Kuetsjarvi in July 1993 were Bipalpus