Bioaccumulation of contaminants in amphibians in historical gold mining areas of Nova Scotia

Abstract

Nova Scotia has a long history of gold mining dating back to the mid-1800’s. Early mining techniques depended on the use of liquid mercury (Hg). As there were little or no environmental regulations at the time, over 3,000,000 tonnes of mine waste (tailings) were released into the environment. These tailings can contain high concentrations of toxic chemicals including Hg and arsenic (As). Such chemicals have negative effects on the environment and on wildlife. Frogs are often used as indicators of environmental conditions. Their thin, permeable skin and semi-aquatic lifestyle can lead to the bioaccumulation of toxins in frog tissues. This study compares bioaccumulation of Hg in frogs collected from six research sites and one reference site from within historical gold mining districts in Nova Scotia, Canada. Dried, ground frog-leg tissues were analyzed for Hg content using a Milestone DMA 80 direct mercury analyzer. This project tests the hypothesis that if concentrations of Hg are high at research sites identified as legacy tailing areas in Nova Scotia, then the concentrations of total mercury content (THg) in the tissues of amphibians collected at the respective sites will also be high. Adult amphibians sampled from contaminated sites had concentrations of THg ranging from 0.1324 - 2.1329 mg/kg. Tadpoles sampled from contaminated sites had concentrations of THg ranging from 0.1384 -15.9412 mg/kg. The THg concentrations in adult amphibians at a reference site ranged from 1.664 – 2.3959 mg/kg. The THg concentrations in tadpoles at the reference site ranged from 0.0494 – 3.3312 mg/kg. These ranges indicate elevated Hg levels in both adult amphibians and tadpoles. This project, as part of the legacy gold mine contaminants research led by the Dynamic Environment and Ecosystems Health Research (DEEHR) team at Saint Mary’s University will enhance the understanding of impacts of historical human activity on aquatic ecosystems.