PREDICTION OF CONTAMINANT ACCUMULATION BY FREE-LIVING ORGANISMS - APPLICATIONS OF A SIGMOIDAL MODEL

The accumulation of contaminants by free‐living organisms has traditionally been determined with permutations of the deterministic model: Ct = Ce(1 – e−kt). However, studies utilizing a variety of species and exposure scenarios now suggest that significant deviations may occur from this classic form. In many cases noted to date, these deviations have involved a sigmoidal pattern of accumulation. While there may be no one single causal mechanism responsible for the expression of such a pattern in all cases studied, the application of a flexibly shaped Richards sigmoidal model can improve goodness of fit to the data relative to the classic model form. Several examples are presented for use of the Richards model: accumulation of 137Cs by free‐living American coots (Fulica americana) and yellow‐bellied turtles (Pseudemys scripta), and Hg accumulation by mosquitofish (Gambusia affinis). Copyright © 1990 SETAC