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

74 A. Lukin et al. / The Science of the Total Environment 306 (2003) 73-83 Fig. 1. Map illustrating the geographic position of Lake Kuetsjarvi and sampling stations. lake is directly exposed both to wastewater dis­ charges and air-borne load. During the seven years (1990-1996) hydro­ chemical, hydrobiological and ichthyological sur­ veys of the Kuetsja Rvi Lake have been carried out. The investigations of the lake were performed during the open water period (summer-autumn). The aim of the present paper is to estimate the state of the lake ecosystem and study its response to intensive anthropogenic load (with the example of lake Kuetsjarvi). 2. Materials and methods Kuetsjarvi (69°26'N, 30o08'E) is an oligotrophic lake belonging to the Pasvik river watershed, incorporated through a narrow strait with lake Salmijarvi (Fig. 1). The greatest length of the lake is 11.6 km, the greatest width 2.8 km, the maxi­ mum depth 32 m, the lake area 17 km2. The lake is located in the forest zone on the border between Russia and Norway. Sediment samples from Lake Kuetsjarvi were collected with an ordinary gravity sediment corer (Skogheim, 1979). Twelve sediment cores from six stations were taken between 1991 and 1994 (Fig. 1). The sediment samples were mainly rep­ resented by fine silt. Two layers were collected from each core: 1 cm thick a top layer showing the present situation in the lake and one layer from a depth of 20-30 cm supplying background metal content values. One core from the middle part of the lake close to the Salmijarvi strait connecting Lake Kuetsjarvi and the Pasvik River (station 3) was sectioned into 1-cm layers for analysis. Chem­ ical analysis techniques were described in more detail elsewhere and some data have already been published (Traaen et al., 1991; Rognerud et al., 1993; Moiseenko et al., 1994, 1995; Dauvalter, 1992, 1994, 1997). To assess the anthropogenic impact on the lake ecosystem, the contamination factor ( C f) was calculated for each heavy metal (Ni, Cu, Co, Zn, Pb, Cd, Hg, Mn, Fe) as the ratio of concentrations from the surface to the back­ ground layer according to Hakanson (1980). Phytoplankton was sampled in July-August 1994 and 1996. Phytoplankton samples were taken from the surface in several localities. After pres