Influence of the energy relationships of trophic levels and of elements on bioaccumulation.

A concern of ecotoxicology is to predict to which trophic levels in biocenoses bioaccumulation of compounds or of elements occurs. Transformity, a measure of the energy required to produce and maintain a component or a flow resulting from an energy transformation process, may help predict bioaccumulation potential. This notion derives from two concepts. First, common substances are more likely to be processed by the biosphere. Moreover, the uptake of rare ones from the physical environment by organisms of low trophic levels makes them less unusual to organisms of high trophic levels, which may evolve a capability of processing them. Second, transformity expresses energy relationships between parts of a system. Substances that require more energy to form or concentrate are also the more unusual. The hypothesis was formulated that there is a correlation between the rarity, complexity, and energy required for concentrating a substance, and thus its transformity, and the transformity of the trophic level to which it bioaccumulates. This hypothesis was tested for a set of elements with published data on their biogeochemistry and bioaccumulation and on energy transfers between trophic levels in ecosystems. The transformities of the elements were calculated from the energy required by the biosphere for maintaining a difference in concentration compared to its physical environment. Transformities of corresponding trophic levels were calculated from the energy driving the energy flows. There was a significant rank correlation between the transformity of elements and that of trophic levels. This may be an important generalization in ecotoxicology because it may lead to the possibility of predicting bioaccumulation tendency.