This chapter addresses the interpretation of accumulated trace metal concentrations in one component of the biota—in this case aquatic invertebrates. Aquatic invertebrates represent key members of the biota of habitats particularly at risk from toxic metal contamination, such as fresh-waters and estuaries receiving metal-laden effluents from mining activities, industrial concerns, and urban and domestic run off. Aquatic invertebrates will also take up metals from ingested food particles, and the diet can indeed be the predominant route of uptake of a trace metal by an aquatic invertebrate. Biodynamic modeling now represents an important tool in determining the relative importance of dissolved and dietary uptake of different metals to different aquatic invertebrates in different habitats under different degrees of metal contamination. Biodynamic modeling allows the prediction and explanation of widely differing accumulated trace metal concentrations in aquatic invertebrates, combining geochemical measurements of environmental metal concentrations with the estimation of key biological parameters.