Sandimirov S. Heavy metal contents in whitefish (Coregonus lavaretus) along a pollution gradient in a subarctic watercourse. Environ. Monit. Assess. 2011, V. 182, №1-4, p. 301-316.

Environ Monit Assess (2011) 182:301-316 311 comparison, a hundred-fold decline was observed in water concentrations and a fifty-fold decrease in sediment levels of Ni from Kuetsjarvi to the three upstream lake sites in the watercourse (i.e. Vaggatem, Rajakoski and Lake Inari). Similar, but less pronounced decreases were also seen for Cu and Cd. The two whitefish morphs generally exhibited very similar concentrations of Ni, Cu, Cd, Zn and Pb in the investigated tissues, and these metals did not increase with fish size or age. In contrast, the Hg concentration increased with increasing age across all investigated tissues, indicating bioaccumulation (i.e. increasing tissue concentrations with age, Wiener and Giesy 1979). The Hg concentration was also significantly higher in DR than in SR whitefish, which likely is a result of their different trophic ecology as higher Hg concentrations typically are found in fish species associated with pelagic rather than benthic food chains (Power et al. 2002; Stewart et al. 2008). An accumulation of Hg through food intake sug­ gests that the contaminant level of this element will increase with increasing trophic level (bio­ magnification), as frequently observed in other freshwater food webs (Watras et al 1998; Chen et al. 2000, 2005; Pickhardt et al. 2005). The ob­ served Hg levels in environment and whitefish tissue were however low relative to findings from comparable sites in Fennoscandia (e.g. Iivonen et al. 1992), and all samples were below the critical limit for human consumption in EU (0.5 ц-g g-1 wet weight). Furthermore, the Hg content in en­ vironment and fish did not exhibit any clear trend with distance from the Nikel smelters, indicating that Hg does not constitute an important pollutant output from the smelter activities. All six heavy metals studied in the present in­ vestigation are potential hazards that can endan­ ger both animal and human health (Mance 1987; Jewett et al. 2003). Knowledge of their concentra­ tions in fish is therefore important both with re­ spect to nature management and human consump­ tion of fish. The exploration and evaluation of heavy metal contents in fish is however a challeng­ ing task as the concentrations in fish tissue appear to be the result of complex interactions of many chemical and biological factors (Wiener and Giesy 1979;McFarlane and Franzin 1980;Dallinger et al. 1987; Iivonen et al. 1992). In contrast to the rel­ atively low concentrations observed for Hg and Zn, the concentrations of the other studied metals appeared to be highly elevated in both environ­ ment and whitefish in Kuetsjarvi. The levels of Ni and Cu observed in the surficial sediments are for instance much higher than background levels observed in Arctic and subarctic lakes with little anthropogenic influence (see e.g. Rognerud and Fjeld 1993; Pacyna 1995; Allen-Gil et al. 1997), al­ though somewhat lower than observed in lakes in the vicinity of the large Sudbury and Norilsk met- allurgic industries (Nriagu et al. 1982; Blais et al. 1999). Furthermore, in the Kuetsjarvi whitefish, the concentration levels of these and other metals were higher than observed in fish from unpolluted to moderately polluted lakes (see e.g. Iivonen et al. 1992; Allen-Gil and Martynov 1995; Allen- Gil et al. 1997, 2003), and similar to levels found in fish near other large metallurgic smelters like in Sudbury and Flin Flon, Manitoba (McFarlane and Franzin 1980; Bradley and Morris 1986). For the other investigated lake sites in the Inari-Pasvik watercourse, the heavy metal concentrations in whitefish were at levels typically observed in lakes with low anthropogenic impacts. The heavy metal concentrations in whitefish showed large differences between the different organs and tissues that were explored (i.e. gill, liver, kidney and muscle). The levels of Ni and Cd were highest in the kidney. Experimental studies with dietary nickel in lake whitefish (Coregonus clupeaformis ) accordingly demonstrated that the kidney is an important target organ for Ni accumulation and toxicity (Ptashynski and Klaverkamp 2002; Ptashynski et al. 2002). Cd is a persistent element that may be toxic to aquatic organisms at relatively low concentrations, but Taylor (1983) considered the bioconcentration of Cd in aquatic vertebrates to be so low that it was likely of little significance. Dallinger et al. (1987), in contrast, pointed out that most heavy metals are biologically significant or even harmful at very low tissue concentrations. The observation that Pb levels decreased with increasing age across all the investigated tissues potentially indicates that high Pb contamination is associated with higher mortality, but we could not find any studies reporting biological effects in fish exposed to Pb levels similar to the ones observed in our study. Springer