Why Is Metal Bioaccumulation So Variable? Biodynamics as a Unifying Concept

Abstract

Ecological risks from metal contaminants are difficult to document because responses differ among species, threats differ among metals, and environmental influences are complex. Unifying concepts are needed to bettertie together such complexities. Here we suggest that a biologically based conceptualization, the biodynamic model, provides the necessary unification for a key aspect in risk: metal bioaccumulation (internal exposure). The model is mechanistically based, but empirically considers geochemical influences, biological differences, and differences among metals. Forecasts from the model agree closely with observations from nature, validating its basic assumptions. The biodynamic metal bioaccumulation model combines targeted, high-quality geochemical analyses from a site of interestwith parametrization of key physiological constants for a species from that site. The physiological parameters include metal influx rates from water, influx rates from food, rate constants of loss, and growth rates (when high). We compiled results from 15 publications that forecast species-specific bioaccumulation, and compare the forecasts to bioaccumulation data from the field. These data consider concentrations that cover 7 orders of magnitude. They include 7 metals and 14 species of animals from 3 phyla and 11 marine, estuarine, and freshwater environments. The coefficient of determination (R2) between forecasts and independently observed bioaccumulation from the field was 0.98. Most forecasts agreed with observations within 2-fold. The agreement suggests that the basic assumptions of the biodynamic model are tenable. A unified explanation of metal bioaccumulation sets the stage for a realistic understanding of toxicity and ecological effects of metals in nature.

Avaliação de contaminação por metais pesados em amostras de siris azuis

“…Este modelo supõe que o processo de bioacumulação é o resultado do balanço de três mecanismos: taxa de entrada pela dieta, taxa de entrada por formas diversas e taxa de perdas pelo organismo 19 . Com isso, novos valores de limites máximos permitidos deverão ser estabelecidos de acordo com a localidade ou região de interesse.…”

Relative importance of direct and trophic uranium exposures in the crayfish Orconectes limosus: Implication for predicting uranium bioaccumulation and its associated toxicity

“…This is referred to as the critical body residues approach [7,[10][11][12][13][14], which focuses on the characterization of metal distribution in organisms. Even if the relationship between bioaccumulation expressed by the metal-available fraction and toxicity remains complex [15][16][17], toxicity is now seen to depend partly on the biological model, the metal, and more accurately, chemical binding of the metal within cells [17,18].…”

Heavy metals in zooplankton and decapod crustaceans from the Barents Sea

“…Thus, the total bioavailable fraction is only accessible by determining the amount of metals incorporated in organisms (Zauke et al, 1996b). The accumulation patterns and subsequent accumulated concentrations in marine organisms are often varying specifically as can be explained and predicted by toxicokinetic modelling (Clason et al, 2004;Luoma and Rainbow, 2005). As a result, we frequently can find different species of zooplankton with greatly varying metal concentrations in the same body of ocean water Petri and Zauke, 1993;Ritterhoff and Zauke, 1997d).…”

“…In order to differentiate human impact from natural variability, knowledge of background concentrations of metals and their fluctuations in biomonitor organisms is essential as well as a thorough understanding of accumulation and detoxification strategies (Luoma and Rainbow, 2005). Those depend on various aspects, including the biological species and element considered, the applied exposure regime, cation homeostasis mechanisms, life-history status, spatial and temporal scales and others.…”