Failed recruitment of southern toads (Bufo terrestris) in a trace element-contaminated breeding habitat: Direct and indirect effects that may lead toa local population sink

We conducted a transplant study in which embryonic southern toads (Bufo ter restris) were held in a site polluted with coal ash (site AB; containing As , Cd, Cr, Cu, Se, and other elements) and a reference site (site R) through hatching and early larval development. To examine the remainder of the lar val period, surviving larvae in AB were then transplanted to R and back-tra nsplanted to AB, whereas surviving larvae from R were back-transplanted to R. Survival through early larval development was lower in AB than in R (34% versus 50%). However, site of hatching did not influence traits later in d evelopment (larval metabolic rate, larval morphology, duration of larval pe riod, size at metamorphosis, or average hopping distance by metamorphs). To ads that spent the entire larval period in R had high rates of survival (70 -94% of individuals transplanted after the embryonic period) regardless of where they spent the embryonic acid early larval period. However, toads hel d in AB for the duration of the larval period suffered 100% mortality. Alga l resources were scarce and their trace element concentrations high in AB c ompared to R, suggesting that mortality of larval toads resulted from a com bination of direct toxicity (via sediment- and foodborne exposure) and indi rect effects on resource abundance. The study suggests that the widespread practice of disposing of coal ash in open aquatic basins may result in sink habitats for some amphibian populations.