Bioaccumulation of contaminants in Scarabaeidae and Silphidae beetles at sites polluted by coal combustion residuals and radiocesium.

Anthropogenic contamination from coal-fired power plants and nuclear reactors is a pervasive issue impacting ecosystems across the globe. As a result, it is critical that studies continue to assess the accumulation and effects of trace elements and radionuclides in a diversity of biota. In particular, bioindicator species are a powerful tool for risk assessment of chemically contaminated habitats. Using inductively coupled plasma mass spectrometry (ICP-MS) and auto-gamma counting, we analyzed trace element and radiocesium contaminant concentrations in Scarabaeidae and Silphidae beetles (Order: Coleoptera), important taxa in decomposition and nutrient cycling, at contaminated and reference sites on the Savannah River Site, South Carolina, U.S. Our results revealed variability in trace element concentrations between Scarabaeidae and Silphidae beetles at uncontaminated and contaminated sites. Compared to Scarabaeidae, Silphidae had higher levels of chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), and zinc (Zn). Unexpectedly, concentrations of Cr, Cu, and Ni were higher in both taxa at the uncontaminated sites. Scarabaeidae and Silphidae beetles at the coal combustion waste site consistently had high concentrations of arsenic (As), and Scarabaeidae had high concentrations of selenium (Se). Of the 50 beetles analyzed for radiocesium levels, two had elevated radioactivity concentrations, both of which were from a site contaminated with radionuclides. Our results suggest carrion beetles may be particularly sensitive to bioaccumulation of contaminants due to their trophic position and role in decomposition, and thus are useful sentinels of trace element and radionuclide contamination.

Effects of industrial disturbances on biodiversity of carrion-associated beetles.

Energy production systems such as nuclear reactors and coal-burning power plants produce a multitude of waste contaminants including radionuclides, trace elements, and heavy metals. Among invertebrates, much of the effort to understand the impact of these contaminants has focused in aquatic environments, while relatively less attention has been on terrestrial communities. We investigated the effects of trace element and radionuclide contamination on assemblages of beetles that are drawn to vertebrate carrion. Samples were collected from riparian sites at the Savannah River Site in South Carolina to compare trap catches (i.e., measure of relative abundance) of beetles and species diversity along a habitat gradient (0-300 m) away from an aquatic habitat and between uncontaminated and contaminated sites. We collected 17,800 carrion-associated beetles representing 112 species in nine families, which were classified as either scavenger or predatory beetles. Beetle catches and species diversity were generally higher at contaminated than uncontaminated sites. These trends were likely driven by scavenger species, which showed similar patterns between sites, whereas patterns of catches and species diversity were variable between sites for predatory beetles. Species compositions of contaminated and uncontaminated sites were generally distinct, however habitat edges appeared to substantially affect beetle assemblages. Overall, our study suggests carrion beetle assemblages are sensitive to edge effects and may exhibit variable responses to the presence of anthropogenic contaminants or disturbances associated with energy production systems. Such results reflect the inherent variability among individual beetle species, populations, and communities to local environmental conditions, and underscores the need for multi-taxa approach in environmental impact assessments.