African fish mercury burden and isotopic composition from archived museum specimens

Fish collected for taxonomic and systematic purposes are often preserved and then archived in museum collections. Preserved fish are commonly first fixed in a formalin solution and then transferred to ethanol for long-term storage. The wet preservation method can potentially introduce mercury (Hg) contamination or unintentionally extract Hg from tissue. An experiment was designed to test the utility of museum preserved fishes in reconstructing spatiotemporal trends in methylmercury (MeHg) concentration and Hg stable isotope ratios, which is used to trace Hg sources to fishes. Wet preserved fish specimens from the Congo River and river basins within Gabon were subsampled from archives at the the Royal Museum of Africa (Belgium). The fish tissue was analyzed for Hg speciation and carbon and nitrogen isotopes.