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Biomagnification of mercury in a West African crater lake (Lake Bosomtwe, Ghana)

Biomass burning, coal combustion, metal processing, and long-range atmospheric transport are important sources of mercury (Hg) to West Africa (UNEP 2002). However, few studies have explored the risks posed by mercury to West African aquatic systems and those who rely on them. To study the trophic transfer of contaminants in aquatic systems, it is critical to understand the underlying food web. Results of stable carbon (Õ13C) and nitrogen (Õ15N) isotopic analyses can be used to characterize food webs and trophic interactions (PETERSON & FRY 1987, FRY 1991), and such data have been successfully applied in food-web contaminant studies in several tropicallakes (CAMPBELL et al. 2003a, Kmo et al. 2003, CAMPBELL et al. 2006). The purpose of this study was to measure mercury in the biota of Lake Bosomtwe (Ghana). Artisanal gold mining (AGM), which uses Hg in its processes and contributes to regional emissions, has been on the rise in Ghana since the early 1980s, and Lake Bosomtwe lies in the Pra River Basin, an important AGM region (DoNKOR et al. 2006). As a result, Lake Bosomtwe is at risk of increased exposure to mercury. This study pairs determination of total mercury (THg) concentrations in biotic samples with the characterization of the Lake Bosomtwe food web using stable carbon {Õ13C) and nitrogen (Õ15N) isotope analyses.