(Table 1) Age, fork length, and tissue d15N and element concentration of arctic char (Salvelinus alpinus) from Lake Hazen

Arctic char (Salvelinus alpinus L.), the top predator in High Arctic lakes, often is used as a bioindicator of Hg contamination in Arctic aquatic ecosystems. The present study investigated effects of trophic position, size, and age of Arctic char in Lake Hazen, the largest lake in the Canadian High Arctic (81°50'N, 70°25'W), on Hg bioaccumulation. In addition, several essential (Se, K) and nonessential elements (Tl, Cs) in char muscle tissue were examined to compare their behavior to that of Hg. Trophic position of Arctic char was identified by stable isotope (d15N) signature. Temporal trends of Hg from seven sampling campaigns over a 16-year period (1990-2006) were investigated for the overall data and for one trophic class. Concentrations of Hg were not correlated with age but were positively related to fork length and trophic position. Large char with greater d15N signatures (>12 per mil) had larger Hg concentrations (0.09-1.63 µg/g wet wt) than small char with smaller d15N signatures (<12 per mil, 0.03-0.32 µg/g wet wt), indicating that Hg concentrations increased with trophic position. Nonessential Cs and Tl showed relationships to age, length, and trophic position similar to those of Hg, indicating their potential to bioaccumulate and biomagnify. Essential Se and K did not show these relationships. Concentrations of Hg were adjusted using d15N, leading to less within-year variability and a more consistent temporal trend. The d15N-adjusted trend showed no decline of Hg in Arctic char from Lake Hazen (1990-2006) in the overall data set and in the small morphotype. Trends for the same period before the adjustment were not significant for the overall data set, but a slight decrease was apparent in the small morphotype. The results confirm the need to consider trophic position and fish size when monitoring temporal trends of Hg, particularly for species with different morphotypes.

(Table 1) Age, fork length, tissue d15N and d13C and mercury content of arctic char (Salvelinus alpinus) across the Canadian Arctic

Among-lake variation in mercury (Hg) concentrations in landlocked Arctic char was examined in 27 char populations from remote lakes across the Canadian Arctic. A total of 520 landlocked Arctic char were collected from 27 lakes, as well as sediments and surface water from a subset of lakes in 1999, 2002, and 2005 to 2007. Size, length, age, and trophic position (d15N) of individual char were determined and relationships with total Hg (THg) concentrations investigated, to identify a common covariate for adjustment using analysis of covariance (ANCOVA). A subset of 216 char from 24 populations was used for spatial comparison, after length-adjustment. The influence of trophic position and food web length and abiotic characteristics such as location, geomorphology, lake area, catchment area, catchment-to-lake area ratio of the lakes on adjusted THg concentrations in char muscle tissue were then evaluated. Arctic char from Amituk Lake (Cornwallis Island) had the highest Hg concentrations (1.31 µg/g wet wt), while Tessisoak Lake (Labrador, 0.07 µg/g wet wt) had the lowest. Concentrations of THg were positively correlated with size, d15N, and age, respectively, in 88,71, and 58% of 24 char populations. Length and d15N were correlated in 67% of 24 char populations. Food chain length did not explain the differences in length-adjusted THg concentrations in char. No relationships between adjusted THg concentrations in char and latitude or longitude were found, however, THg concentrations in char showed a positive correlation with catchment-to-lake area ratio. Furthermore, we conclude that inputs from the surrounding environment may influence THg concentrations, and will ultimately affect THg concentrations in char as a result of predicted climate-driven changes that may occur in Arctic lake watersheds.