Modeling the Individual and Interactive Risks to an Amphibian Population Resulting from Breeding Site Contamination and Terrestrial Habitat LossEPA Grant Number: R829087
Title: Modeling the Individual and Interactive Risks to an Amphibian Population Resulting from Breeding Site Contamination and Terrestrial Habitat Loss
Investigators: Rowe, C. L. , Hopkins, William A.
Institution: University of Maryland , University of Georgia
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2002 through December 31, 2003 (Extended to December 17, 2004)
Project Amount: $280,059
RFA: Wildlife Risk Assessment (2001) RFA Text | Recipients Lists
Research Category: Biology/Life Sciences , Ecological Indicators/Assessment/Restoration , Ecosystems
The status of many amphibian populations worldwide is an issue of great concern, yet rigorously assessing the population dynamics of these animals has proven difficult due to the complexity of their life cycles. As a result, the influences of human activities on amphibian populations are poorly understood. Because many amphibians occupy specific habitat types during different stages of the life cycle (aquatic embryos/larvae, terrestrial juveniles/adults), anthropogenic activities occurring in different habitats may interact to affect amphibian populations via impacts at various life stages. Thus, to understand population-level responses of amphibians to anthropogenic stresses, it is necessary to integrate responses across habitat types and life stages, and ultimately generate population models that reflect spatial and temporal effects.
The proposed project will examine a population of eastern narrow-mouth toads inhabiting the Savannah River Site, SC, where they may be affected by many different human activities, including chemical contamination of aquatic habitats and modification of natural terrestrial habitats. Specifically, the project will examine the influences of exposure to contaminants during aquatic life stages and reductions in per capita habitat availability during terrestrial life stages on population dynamics. The project will combine original, experimental research with existing data to assess habitat- and life stage-specific stresses, ultimately generating stage-based matrix population models with which individual and interactive effects of the stresses will be compared. A model based upon existing data for juvenile and adult responses to per capita reductions in available terrestrial habitat indicates that survival and growth during early life stages are critical to population dynamics. Therefore, an objective of the project is to quantify the effects of aquatic contamination on early life stages, thus allowing parameterization of population models to rigorously assess aquatic and terrestrial stresses individually and interactively. Experiments will be conducted in an aquatic site contaminated by coal combustion wastes which is heavily used by the population for breeding and has been extensively studied by the PIs. Results for other amphibian species indicate that survival, growth, and performance of larvae in the contaminated site are substantially reduced, yet rigorous, population-level analyses have not been attainable due to insufficient information on terrestrial juveniles and adults. The proposed project will provide for such an integrated assessment of the local population because it will incorporate empirical data from studies of both the aquatic and terrestrial life stages. The project will thus provide a holistic evaluation of amphibian population responses to anthropogenic stresses based upon empirical data.
While the project will specifically address real-world risks to the local population of narrow-mouth toads, it will also serve as a model to guide future examinations of amphibian population dynamics in ecological, toxicological, conservation, and risk assessment contexts.