Exposure to trace elements has negative reproductive consequences for southern toads (Bufo terrestris) exposed to coal combustion waste
Metts, Brian Sears
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Bioaccumulation of contaminants and subsequent maternal transfer to offspring could be an important factor that affects amphibian reproduction and embryonic development. My research is among the few to investigate the individual and interactive effects of paternal and maternal exposure to contaminants on amphibian reproductive success, and to document relationships between contaminant concentrations in female amphibians or their eggs and reduced reproductive success. Specifically, southern toads (Bufo terrestris) exposed to coal combustion waste (CCW) accumulated several trace elements (e.g. selenium). Exposure to trace elements was associated with adverse effects on clutch size, embryo viability, and overall reproductive success. Compared to reference, reproductive success was reduced by 40% when either the male or the female was from the ash basin and by 58% when both parents were from the ash basin. Reproductive success was negatively correlated with Se concentrations in females and their eggs. In addition, this research demonstrates negative effects of larval exposure to CCW contaminated sediments, latent effects of maternal exposure to CCW derived contaminants, and their interactive effects. Most notably, survival to metamorphosis was reduced dramatically in larvae from females collected near CCW contaminated settling basins; however, the degree of this reduction was dependent on the type of sediment that their larvae developed on. Survival of larvae from contaminated females was lowest when reared on ash basin sediments but highest when reared on ash plume sediments. Negative sublethal effects on larvae (e.g., extended larval period) were attributable to sediment type during the larval period, and not previous maternal exposure. Interestingly, sublethal effects were less pronounced in larvae reared on ash plume sediments compared to ash basin sediments, suggesting the effects may decrease as sediments age. However, larval survival was substantially reduced by exposure to ash plume sediments. My research highlights the need for additional studies investigating the effects of exposure to contaminants on amphibian reproduction. It underscores the importance of further research investigating potential latent effects from contaminant exposure, particularly post-metamorphosis. My study provides evidence that CCW contaminated sites may ultimately serve as ecological traps, and highlights the importance of understanding how individual effects impact local amphibian population viability.