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 81 ko et al., 1994). These fluctuations are related to the high content of nutrients in the water (total phosphorus> 15 mg l -1, total nitrogen>180 mg l -1). During mass development of plankton algae, a reduction of Si content in the water down to 0.7 mg l -1 was often observed. These data indicated that Kuetsjarvi is a eutrophic lake. This conclusion is corroborated also by frequent mass development of species typical of eutrophic lakes (Asterionella formosa, Fragilaria capucina). Absence of season­ al successions and significant fluctuations of the total volume prove the phytoplankton community to be unstable, which can be explained by intensive anthropogenic loading of the lake. Exceptionally high zooplankton biomass (> 2000 mg m -2 dry wt.) was recorded in Lake Kuetsjarvi in 1990. It was associated with high productivity in the lake (Nost et al., 1992). How­ ever, in 1991-1992 the biomass reduced to approximately 500 mg m -2 dry weight. This was due to much lower numbers of B. longirostris and D. cristata in the past years—a reduction which could be explained by changes in planktivorous fish predation pressure on zooplankton and nega­ tive impacts of pollution (Nost et al., 1992; Langeland et al., 1993; Moiseenko et al., 1994). The biomass level in 1993 was not high (0.35 g m -3 ww). High biomass was recorded in the southern part in 1994 due to the abundance of large-sized cladocerans (Bosmina longispina , Daphnia cristata) and copepods (Eudiaptomus gracilis). Low biomass level (0.27 g m -3 ww) in the northern part in June 1996 were probably associated with high numbers of small-sized Rota­ toria. Lower abundance of Cladocera and Cope- poda, and possibly with low water temperatures (8.6 °N) in the study period, which could cause a shift of the growing season of large-sized Clado- cera and Copepoda. The high density and biomass of zoobenthos represented mainly by pollution-tolerant chiron- omids, tubificidae worms is another indication of increased concentrations of nutrients and contam­ ination. Invertebrate species sensitive to water contamination (mayflies, Tanytarsini and Ortho- cladiinae chironomids) occurred in littoral and deep sites only at considerable distance from the Kolosjoki stream mouth. The highest metal (particularly Ni and Cu) concentrations in invertebrates reflect the increased content of those metals in the water and lake sediments. Nikanorov and Julidov (1991) reported maximum concentration of Ni in aquatic biota in Russia to be 144 mg g -1 . Exactly the same level was found in our study for Polycentropodidae caddisflies. For a comparison, only the mean concentration of Zn was higher in 56 small lakes of Finnish Lapland studied in 1993-1994, and the distribution was Zn > Cu > Ni > Pb > Cd > Co. The European vendace Coregonus albula (L) is a new fish species for the Pasvik river system. This species was acclimatized in Lake Inari, from which the Pasvik river flows, and in recent years has migrated via the system of reservoirs down­ stream (Amundsen and Staldvik, 1993; Amundsen et al., 1993). In our catches from Lake Kuetsjarvi vendace was first found in 1995. European white- fish Coregonus lavaretus (L) is represented in the lake by two ecological forms (Lukin and Kashulin, 1991). One of them is a typical sparsely rakered (16-32) pydschjan whitefish, feeding mainly on benthos, which can be attributed to the subspecies C. lavaretus pidschian (Gmelin). The second form is a densely rakered (32-42) whitefish with the prevalence of zooplankton in the diet, which can be attributed to the subspecies C. lavaretus medios- pinatus (Pravdin) (Reshetnikov, 1980; Reshetni- kov and Amundsen, 1994). The results of our research show that the accu­ mulation of nickel is proportional to Ni load (volume of nickel deposited in the water ecosys­ tem from the Nickel smelter) (Fig. 6). Cu accu­ mulation pattern is more complex (Fig. 7). The accumulation of Zn is reciprocal to Ni load and clearly suppressed by the level of pollution (Fig. 8). The level of Cu and Zn in the fish examined was below that in the control fish. Data from the literature (Harmful chemical substances, 1989; Larskiy, 1990) and analysis of our own data suggest that Ni is the principal determinant of the concentrations of other investigated metals, and is the best indicator for this type of pollution. There­ fore, the index of fish kidney Ni concentration can be used for environmental monitoring in this region.