Regional and inter annual patterns of heavy metals, organochlorines and stable isotopes in narwhals (Monodon monoceros) from West Greenland.

Samples of 150 narwhals obtained in different years from two West Greenland areas, Avanersuaq and Uummannaq, were compared for concentrations of and regional differences in heavy metals and organochlorines and stable-carbon and nitrogen isotopes. Cadmium, Hg, and Se concentrations increased in the first 3-4 years of the animal's life, after which no dependence on age was observed. Females had significantly higher concentrations of Cd in all tissues and of Hg and Se in liver than males. No consistent difference in metal levels between narwhals from Avanersuaq and Uummannaq was found. Year-to-year variation in metal levels at one location was larger than the geographical variation. Metal levels were within the range of previous published results for narwhals from Arctic Canada. Organochlorine (OC) concentrations in blubber of narwhals were dependent on age and sex. Females showed decreasing OC concentration in the first 8-10 years, while for males increases were detected in the first few years of life, after which the concentrations became stable. Few statistical differences in mean OC concentrations among individuals were observed. However, narwhals from Avanersuaq in 1993 had the lowest levels, indicating a temporal decrease of SigmaPCBs. SigmaPCBs, DDTs, HCHs and toxaphenes seem to be at similar levels in West Greenland and Arctic Canada, which can be explained by the close winter distributions of populations as well as large ranges in concentrations, time span, number of analyses and the size/age composition of the data. PCB and DDT concentrations in West Greenland narwhals were half those found in East Greenland and Svalbard. Stable-carbon isotope ratios in muscle of 150 narwhals showed a decreasing trend in the first year when they gradually reduced their dependency on mother's milk, after which they became relatively stable. delta15 N values were significantly higher in samples from Uummannaq in 1993 compared to samples from Avanersuaq in 1984 and 1985 indicating that the diet of the narwhals in Uummannaq was at a higher trophic level. However, only a few significant correlations were found between stable isotope ratios and metal and OC concentrations.