Integrating Individual-Based Indices of Contaminant Effects

Abstract

Habitat contamination can alter numerous biological processes in individual organisms. Examining multiple individual-level responses in an integrative fashion is necessary to understand how individual health or fitness reflects environmental contamination. Here we provide an example of such an integrated perspective based upon recent studies of an amphibian (the bullfrog, Rana catesbeiana) that experiences several, disparate changes when larval development occurs in a trace element–contaminated habitat. First, we present an overview of studies focused on specific responses of individuals collected from, or transplanted into, a habitat contaminated by coal combustion residues (CCR). These studies have reported morphological, behavioral, and physiological modifications to individuals chronically interacting with sediments in the CCR-contaminated site. Morphological abnormalities in the oral and tail regions in contaminant-exposed individuals influenced other properties such as grazing, growth, and swimming performance. Behavioral changes in swimming activities and responses to stimuli appear to influence predation risk in the contaminant-exposed population. Significant changes in bioenergetics in the contaminated habitat, evident as abnormally high energetic expenditures for survival (maintenance) costs, may ultimately influence production pathways (growth, energy storage) in individuals. We then present a conceptual model to examine how interactions among the affected systems (morphological, behavioral, physiological) may ultimately bring about more severe effects than would be predicted if the responses were considered in isolation. A complex interplay among simultaneously occurring biological changes emerges in which multiple, sublethal effects ultimately can translate into reductions in larval or juvenile survival, and thus reduced recruitment of juveniles into the population. In systems where individuals are exposed to low concentrations of contaminants for long periods of time, research focused on one or few sublethal responses could substantially underestimate overall effects on individuals. We suggest that investigators adopt a more integrated perspective on contaminant-induced biological changes so that studies of individual-based effects can be better integrated into analyses of mechanisms of population change.

Efectos subletales de la exposición al vertido tóxico de Aznalcóllar en aves de larga vida

“…Por lo general, una adecuada evaluación de la exposición y efectos de los contaminantes ambientales requiere de la utilización de un conjunto o batería de biomarcadores, cuyas respuestas constituyen evidencias en las que apoyar dicha evaluación o valoración (Rowe et al 2001, Hagger et al 2006. La selección de los biomarcadores a estudiar y las pruebas diagnósticas (tests) empleadas dependerá en gran medida de la naturaleza del problema a tratar y de posibles condicionamientos locales (p.ej.…”

Developing methods to assess and predict the population level effects of environmental contaminants

“…The use of energetics has been suggested also by Widdows and Donkin (1991) and deCoen and Janssen (2003a, 2003b. Rowe et al (2001) make a case for integrating some biological responses from different systems (i.e., morphologic, physiologic, and behavioral) with bioenergetics for a broader view of contaminant effects. It would be unlikely that an assortment of physiologic responses that assess different systems would be susceptible to the same confounding effects, such as gender.…”

“…The complications imposed by interactions between contaminant effects and density feedback merely scratch the surface. Toxicant doses that cause no discernible effects in the lab might exert subtle physiologic adjustments that lower an organism's ability to find food, hold a territory, or escape predation (Rowe et al 2001; Stark and Banks 2003). These effects become perceptible when evaluated at the population level.…”