Bioaccumulation of metal pollutants and radionuclides in dragonflies (Odonata)

Inorganic pollutants released into aquatic habitats by human activity, such as metals and radionuclides, present a serious threat to biodiversity and ecosystem health. Various biomonitoring efforts were established to track their release and environmental concentrations, including sampling of bioindicator species, which can accumulate these pollutants and facilitate their detection. Dragonflies (order Odonata) are considered valuable bioindicator organisms due to their relative longevity and predatory lifestyle, and have been used to assess environmental concentrations of a wide variety of pollutants. However, there is a lack of systematic effort to determine which elements are likely to be accumulated in dragonfly tissue from surrounding water, and how the concentrations of accumulated materials correlate to their environmental concentrations. In this review, studies that used dragonflies as bioindicators for metals and radionuclides in aquatic environments were analyzed, and bioaccumulation factors for each element were calculated. The highest bioaccumulation factors were obtained for U and Cs, elements with the highest numbers of bioaccumulation studies were Hg and Cu, and Se was the most consistently accumulated element in analyzed studies. The results have shown that dragonflies are suitable bioindicator organisms for a variety of different radioactive and non-radioactive elements, and calculated bioaccumulation factors provide a link between their presence in dragonfly tissue and the environmental concentrations in their habitats.