(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.

北极红点鲑（Arctic char, Salvelinus alpinus L.）是高北极湖泊中的顶级捕食者，常被用作北极水生生态系统汞（Mercury, Hg）污染的生物指示物。本研究以加拿大高北极地区最大的湖泊黑曾湖（Lake Hazen，81°50'N，70°25'W）中的北极红点鲑为研究对象，探讨其营养级（trophic position）、体型与年龄对汞生物累积（bioaccumulation）的影响。此外，本研究还检测了红点鲑肌肉组织中的几种必需元素硒（Selenium, Se）、钾（Potassium, K）与非必需元素铊（Thallium, Tl）、铯（Cesium, Cs），以对比其与汞的行为特征。北极红点鲑的营养级通过稳定同位素（stable isotope）δ¹⁵N信号进行确定。本研究基于1990-2006年这16年间的7次采样活动所获的全部数据与单一营养级数据，探究了汞的时间变化趋势。结果表明，汞浓度与年龄无显著相关性，但与叉长（fork length）及营养级呈显著正相关。δ¹⁵N信号值高于12‰的大型红点鲑，其汞浓度（0.09~1.63 μg/g 湿重）显著高于δ¹⁵N信号值低于12‰的小型红点鲑（0.03~0.32 μg/g 湿重），表明汞浓度随营养级升高而增加。非必需元素铯（Cs）与铊（Tl）同样表现出与年龄、体型及营养级的相关性，且变化趋势与汞一致，提示二者具备生物累积与生物放大的潜力。而必需元素硒（Se）与钾（K）则未呈现此类相关性。通过δ¹⁵N对汞浓度进行校正后，年内变异度得以降低，时间变化趋势也更为稳定一致。经δ¹⁵N校正后的趋势显示，1990-2006年间，黑曾湖北极红点鲑的汞浓度在全部数据集与小型形态型（morphotype）群体中均未出现下降。未进行校正的同期数据中，全部数据集的汞浓度变化趋势未达显著水平，但小型形态型群体则呈现出轻微的下降趋势。本研究结果证实，在监测汞的时间变化趋势时，需考虑营养级与鱼类体型的影响，对于存在不同形态型的物种而言尤为如此。