The role of coal combustion waste as a stressor in the southern toad, Bufo terrestris

Environmental pollutants have become ubiquitous components of many ecosystems. Many of these pollutants have wide-ranging effects from cellular to population levels and almost all of them are known to cause a stress response in exposed animals. The normal stress response involves a highly conserved suite of physiological mechanisms vertebrates use to mitigate homeostatic disturbance. It is highly adaptive in the short term, but if stress becomes chronic, some of the induced mechanisms become deleterious. This can lead to an increased energetic maintenance cost, immunosuppression, and adrenal and reproductive dysfunction. This study examined the effects of trace metals found in coal combustion waste (coal fly ash) on several critical physiological parameters in the southern toad, Bufo terrestris. I assessed the effects of coal fly ash exposure on metabolism, corticosterone and testosterone levels. I also monitored the levels of trace metals over time and assessed the protective potential of corticosteroid-binding globulin.; To examine these effects, male toads were collected, bled, and weighed in early spring from two sites, a coal fly ash basin and an uncontaminated control site. The toads were then divided into four groups: toads collected at the control site and maintained on either control substrate and food, or coal fly ash substrate and contaminated food and toads collected at the contaminated site and maintained on either control substrate and food, or coal fly ash substrate and contaminated food. All toads were kept outdoors in 2001 mesocosms.; Toads exposed to coal fly ash sequestered significant amounts of trace metals. The increase in metal concentrations in toads tended to peak around 4 weeks of exposure. This increase in metals coincided with a spike in corticosterone, indicating a stress response. None of the other parameters (standard and exercise metabolism, glucose, or testosterone) we measured seemed to be affected by ash exposure, although toads exposed to ash did gain less body mass when food was limited, when compared with control toads. Corticosteroid-binding globulin increased with the increase in corticosterone at 4 weeks of exposure but did not ameliorate the corticosterone spike. Toads exposed to ash did accumulate metals, and responded physiologically to the increased metal load, but I did not measure any deleterious effects associated with exposure.