T7 PM Metals and Bioaccumulation
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 327-329

(GAN-1117-551675) Mercury concentrations in Salvelinus alpinus from Lake Hazen (Nunavut), effects of size and trophic position.

Gantner, N¹, Koeck, G², Babaluk, J³, Reist, J³, Lockhart, W³, Solomon, K¹, Muir, D^{1, 3}, ¹ University of Guelph, Guelph, Ontario, Canada² University of Innsbruck, Innsbruck, Austria, Austria³ Freshwater Institute, Department of Fisheries and Oceans, Winnipeg, Manitoba, Canada

ABSTRACT- Arctic char (Salvelinus alpinus), the top predator of High Arctic lakes, is often used as bioindicator of mercury (Hg) contamination in Arctic aquatic ecosystems. Concentrations of Hg in muscle tissues of landlocked char have been shown to exceed the Health Canada Guideline for subsistence consumption (0.20 g g-1 wt weight) in some lakes in the Canadian Arctic. Purpose of this study was to identify effects of size and feeding ecology (trophic position) of Arctic char in Lake Hazen, the most northerly large lake in Canada (81°50′N; 70°25′W), on Hg bioaccumulation and thereby allow better interpretation of temporal trends of Hg contamination. The feeding ecology of the char was identified by analysis of stomach contents and their trophic position measured with stable isotope ¹⁵N and ¹³C signature, revealing three different morphotypes. Total Hg was measured in dorsal muscle tissue. Total Hg concentration was then related to trophic position, size and age of the sampled fish. Temporal trends over a 12 year period (1992 – 2004) for two size classes were identified. Larger individuals (>375mm fork length) with higher ¹⁵N signature (>12) had greater Hg concentrations (THg, 0.24 – 0.78 g g-1 ww) than smaller individuals (<375mm fork length) with lower (<12) ¹⁵N signature (THg, 0.11 – 0.18 g g-1 ww), indicating that feeding ecology (trophic position) plays a key role in causing differences in Hg bioaccumulation. In comparison to feeding ecology and size, age seemed to play a smaller role. Our results from Lake Hazen suggest that future studies monitoring temporal trends of Hg bioaccumulation must be carried out carefully in regard to age, size and trophic position.

Key words: Salvelinus alpinus, trophic position, mercury, bioaccumulation