Influence of Wetland Degradation on Amphibian Limb Malformations: Interactions Among Parasite Infection, Pesticide Contamination, and Eutrophication

EPA Grant Number: F5E11185
Title: Influence of Wetland Degradation on Amphibian Limb Malformations: Interactions Among Parasite Infection, Pesticide Contamination, and Eutrophication
Investigators: Lunde, Kevin B.
Institution: University of California - Berkeley
EPA Project Officer: Lee, Sonja
Project Period: August 8, 2005 through August 31, 2007
Project Amount: $107,126
RFA: STAR Graduate Fellowships (2005) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


The recent increase in severely malformed amphibians across the United States has caused concern among both scientists and the public. Reports of malformed amphibians date back to the 1700s, yet these occurrences appeared to be geographically and temporally isolated. In contrast, malformed amphibians have now been recorded in 48 states and 60 amphibian species. At some ponds nearly 90% of emerging frogs are deformed. Further, historical comparisons suggest that amphibian malformations are on the rise in distribution, abundance, and severity. Although many agents are capable of altering amphibian limb development, only two have been consistently implicated as causes of widespread malformations: trematode parasites and water-borne contaminants. This project will investigate the independent and synergistic effects of these agents on amphibian limb malformations.

The overarching question is: What are the mechanism(s) through which wetlands loss and artificial pond creation promote increases in amphibian malformations? In particular, this project will explore the additive, synergistic, or antagonistic interactions among cultural eutrophication, parasite infection, and pesticide contamination between natural and artificial wetlands. The hypothesis is that artificial habitats, which are commonly associated with agriculture or livestock, have become a nexus between amphibians and deformity-causing agents.


To investigate the mechanistic links between artificial wetlands and malformed amphibians, this project will use a combination of GIS analyses, intensive field surveys, and controlled mesocosm experiments. This multi-level approach is designed to answer the following questions: a) Are malformed amphibians more common among randomly selected artificial wetlands relative to natural wetlands? b) How have wetlands loss and artificial pond creation affected malformations at the local level? c) How do parasites, pesticides, and cultural eutrophication interact to drive this pattern? d) How have natural wetland loss and artificial pond creation contributed to increasing the number of potential wetlands supporting malformations?

Expected Results:

Malformed amphibians should be more common on artificial wetlands and that loss of natural wetlands has pressured additional wildlife onto these suboptimal habitats. Further, such sites are more likely than their natural counterparts to have elevated nutrient levels and contain pesticides. This project will tease apart the independent and combined ability of these agents to induce amphibian limb malformations. Another expectation is that low and moderate levels of pesticides probably stress amphibian larvae, reducing their immune response. In such circumstances these amphibians will suffer from higher infection intensities and have a greater likelihood to develop severe and debilitating limb malformations.

Supplemental Keywords:

Amphibians, parasites, nutrients, pesticides, wetlands,, RFA, Scientific Discipline, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, amphibians, Aquatic Ecosystem, Aquatic Ecosystems, Environmental Monitoring, Ecology and Ecosystems, eutrophication, frogs, aquaculture, ecosystem monitoring, toxicity studies, toxicology, amphibian malformations, parasitic infestations, pesticides, predators, multiple stressors, environmental stress, wetland degradation

Progress and Final Reports:

  • 2006
  • 2007
  • Final