Concentration of nickel.

In all fish species caught in the affected area the concentration of nickel in the tissues were significantly higher compared to fish from control waters. The highest concentration of this metal was observed in the kidneys and gills of fish from the Kuetsijavre Lake, and it declined as the distance from the source of the pollution increased. There is a strong positive correlation between the factor of nickel pollution of sediments (Cf) and nickel concentrations in the kidneys of fish.

Dependence of Ni concentrations in the kidneys of fish (mg/g dry wt) versus factor of nickel pollution of sediments (Cf)

In the muscles and liver this relationship is not significant.

In different species of fish, nickel is accumulated in different organs in various amounts. Thus, in the Kuetsijavre Lake, it was distributed in the organs of different fishes in the follow sequence:
Northern pike: kidneys > gills > liver > skeleton > muscles;
Perch: gills >> kidneys > skeleton > liver > muscles;
Whitefish: kidneys > gills > skeleton > liver > muscles.

For all species, the concentration of nickel was high in the kidneys and gills and low in the muscles, where the concentrations of nickel were virtually identical in all species and was not changed in different water bodes. In fishes from the control waters, as in whitefish and pike, the greatest relative concentrations of nickel were observed in the gills.

The levels of nickel accumulation were various for different species of fish:
benthic whitefish > pelagic whitefish > pike>
Muscles: perch > pike > benthic whitefish > pelagic whitefish
Liver: benthic whitefish > pelagic whitefish > pike > perch
Kidneys: benthic whitefish > pelagic whitefish > pike
Skeleton: benthic whitefish > pelagic whitefish > perch > pike

Concentration of copper.

For the investigated species of fish, the highest concentrations of cooper were found in whitefishes: benthic whitefish > pelagic whitefish > pike > perch. The tissue distribution of this metal in different fishes is similar: liver >>> kidneys >> gills > skeleton > muscles. The greatest concentrations of copper are found in the liver, and the lowest in the muscles.

No direct correlation was found between accumulation of copper in fish and the level of lake pollution.

Dependence of Cu concentrations in liver of fish (mg/g dry wt) versus factor of nickel pollution of sediments (Cf)

It should be noted that in the Kuetsijavre Lake, near the source of the pollution, the concentration of copper in fish was lower or equal to control or to it value in fish captured from more remote region. Generally, the concentration of copper was below the control levels despite the fact that the concentration in the sediments exceeded the background level.

Concentration of zinc.

In the fish investigated, the concentration of zinc in the organs and tissues was highly variable. This metal is accumulated in the greatest quantities compared to the others, despite its relatively low concentration in the water. However, the concentration of zinc in the liver was lower then in control fishes, and decreased as the sample site approached the source of pollution. The concentration of zinc in gills and kidneys of whitefish captured near the source of pollution were higher then in the control fishes, but lower then in fishes from the upper reaches of the Pasvik River. The lowest concentrations of zinc were found in the muscles.
Dependence of Zn concentrations in liver of fish (mg/g dry wt) versus factor of nickel pollution of sediments (Cf)

The quantity of metals in the organs and tissues of fish are determined by the complex interaction of external environmental factors (environmental concentration of the metals, water hardness, pH, feeding habits, etc.) and metabolic processes in the organism (absorption, distribution in the organism, redistribution, biotransformation of organometallic compounds, accumulation and excretion). Even more complicated are the interrelationships of different metals inside the organism, which depend on the chemical activity of the metal and its competitive capability in interacting with organic substrates on membranes and inside cells. Thus, in a living organism, nickel interacts with calcium, magnesium, iron, and other metals. In our case, most important is its interaction with copper and zinc. There is a lot of the evidens about the antagonistic interrelationships between nickel and cooper, which are explained not only by the competition for general protein carriers but also by the capability of nickel to replace copperisomorphically in various cell metabolites (Vrednye khimicheskiye veshchestva ..., 1989; Larskiy, 1990). The results of our research show, that the accumulation of nickel is proportional to the laud of nickel. The accumulation of zinc is recprocal to the laud of nickel and clearly suppressed by the level of pollution. Accumulation of copper is more complex. The level of copper and zinc in the investigated fishes was below that in the control fishes. Being based on data from the literature and analysis data received in our researches, it is possible to draw a conclusion that nickel is the principal determinant of the concentration of the other investigated metals and is the best indicator of this type of pollution. Therefore the index of fish kidney nickel concentration may be used for environmental monitoring for this region.

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