Trace elements in bivalve shells: Records of contamination or contaminated record?

W.A. Shoults-Wilson, A. Fritts, J. Unrine, M. Fritts, A. Casper

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Since the establishment of long-term bivalve biomonitoring programs (aka “Mussel Watch” programs) interest has remained in using bivalve shells as indicators of anthropogenic release of toxic trace elements. While many authors have included these analyses without question, the literature is filled with questions about the utility of whole-shells as biomonitors of pollution. In order to answer this question, a meta-analysis of the literature was First performed. According to that analysis, bivalve shells may be suitable for only a handful of elements of concern such as Co, Cu, Mn and Pb, while they appear to be unsuitable for Fe and Hg. The greatest strength of bivalve shells appears to be in provid-ing a lower variability indicator of bioavailable trace elements. In order to validate the meta-analysis for freshwater bivalves, element concentra-tions were studied in native bivalve shells from modern, historic and prehistoric collections within the Illinois River System. These collections demonstrated the importance of shell allometry and bivalve species on within-shell accumulation. It also demonstrated significant trends in accumulation over a century of collection that reªects the rise in indus-trialization (Co and Ni) and a shift to organic pesticides (As). However, archaeological samples may indicate that prehistoric loads of some trace elements (Cd) were higher than modern loads. Spatial gradients in trace elements such as Mn appear to reflect a difference in river chemistry rather than anthropogenic loading. The most important confounding factor appears to be mussel age, indicating that studies which do not take this into account may draw unsupported conclusions. In a companion study, Dreissena polymorphashells from Lake Michigan were compared to tissues, demonstrating that shell concentrations are less variable than tissues both spatially and seasonally. These results validated the literature meta-analysis and indicated that while these shells are likely useful for monitoring As, Cd, Co, Cu, Mn, Ni, and Zn in freshwaters, they are not highly useful in monitoring Al, Cr, Hg, Pb and V
Original languageEnglish (US)
Title of host publicationSociety of Environmental Toxicology and Chemistry North America 36th Annual Meeting, 1-5 November 2015, Salt Lake City, Utah
StatePublished - 2015


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