BIOMAGNIFICATION AND BIOACCUMULATION OF MERCURY IN AN ARCTIC MARINE FOOD-WEB - INSIGHTS FROM STABLE NITROGEN ISOTOPE ANALYSIS

Several recent studies have shown that the use of delta(15)N analysis to characterize trophic relationships can be useful for tracing biocon taminants in food webs. in this study, concentration of total mercury was measured in tissues from 112 individuals representing 27 species f rom the arctic marine food web of Lancaster Sound, Northwest Territori es. Samples ranged from particulate organic matter through polar bears (Ursus maritimus). Using delta(15)N values to identify trophic positi on, we found that total mercury in muscle tissue biomagnified in this food web. Polar bears were a notable exception, having a lower mean me rcury concentration than their main prey ringed seals (Phoca hispida). Most vertebrates showed greater variance in mercury concentration tha n invertebrates, and there was a trend in seabirds toward increased va riability in mercury concentration with trophic position. Within speci es, we found no evidence of bioaccumulation of mercury with age in the muscle tissue of clams (Mya truncata) or ringed seals. Because stable nitrogen isotopes illustrated the relationship in this biome between trophic position and mercury level on a continuous, quantitative scale , we were able to determine that log(10)[Hg] (mu g/g dry weight) = 0.2 (delta(15)N)- 3.3. The measurement of delta(15)N values and mercury co ncentration allowed us to quantitatively assess mercury biomagnificati on within this extensive arctic marine food web.