M9 PM Multiple Stressors in Amphibian and Reptile Ecotoxicology
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 339-340

(ROW-1117-568038) Temporally- and Spatially-Disparate Influences of Anthropogenic Stressors on Amphibian Populations: Effects of Aquatic Contaminants and Terrestrial Habitat Reduction.

Rowe, C¹, Hopkins, W², Salice, C³, Pechmann, J, ¹ University of Maryland Center for Environmental Science, Solomoms, MD² Virginia Polytechinic University, Blacksburg, VA³ U.S. Environmental Protection Agency, Washington, DC

ABSTRACT- The complex life cycles exhibited by most extant amphibians results in susceptibility to environmental stressors operating at temporally- and spatially-distinct scales. The relatively brief aquatic life stages of many species limits the duration of exposure to conditions in aquatic habitats, and the spatially-limited nature of such habitats may provide exposures to stressors unique to the breeding site. On the other hand, long-lived adults dispersing into terrestrial habitats may experience landscape-scale disturbances operating over much longer periods of time. Focusing on the eastern narrowmouth toad (Gastrophryne carolinensis), we combined novel and existing data to construct matrix population models to examine potential influences of aquatic habitat contamination and reduced per capita availability of terrestrial habitat on projected population growth rates. Under conditions of low terrestrial habitat availability and contamination of the aquatic habitat, population growth rate was primarily influenced by survival through the first year (embryos, larvae, terrestrial metamorphs), followed by survival through year 2 (terrestrial juveniles). Under conditions of high terrestrial habitat availability and contaminated aquatic conditions, population growth rate was also primarily influenced by survival through the first year, however survival through ensuing years was relatively unimportant. When examined individually, aquatic contamination had a greater influence on population growth rate (33 % reduction) than did terrestrial habitat restrictions (19 % reduction). With respect to contaminants, larval survival had the greatest influence on population growth compared to reductions in hatching success and fecundity of females inhabiting the contaminated site. The combined influences of aquatic contamination and reduction in terrestrial habitat reduced projected population growth rates by 46 % compared to optimal conditions. Our study emphasizes the importance of considering multiple sources of stress operating at distinct temporal and spatial scales when attempting to identify potential correlates with amphibian population declines.

Key words: population model, amphibian, coal combustion wastes, habitat degradation