Ratio of concentrations of a compound at two consecutive trophic levels at steady state. It can also be expressed in terms of a rate constant-based bioaccumulation model \[B = C_{n}/C_{n-1} = \alpha f/k_{\rm{e}}\] where \(\alpha\) is assimilation efficiency, \(f\) is feeding rate, and \(k_{\rm{e}}\) is the first-order elimination constant. \(B\) can be calculated from field data on assumed trophic relations or from laboratory feeding experiments.