Metal toxicity, uptake and bioaccumulation in aquatic invertebrates--modelling zinc in crustaceans.

We use published data on the different patterns of the bioaccumulation of zinc by three crustaceans, the caridean decapod Palaemon elegans, the amphipod Orchestia gammarellus and the barnacle Amphibalanus amphitrite, to construct comparative biodynamic models of the bioaccumulation of zinc into metabolically available and detoxified components of accumulated zinc in each crustacean under both field and laboratory toxicity test conditions. We then link these bioaccumulation models to the onset of toxic effects on exposure of the crustaceans to high dissolved zinc bioavailabilities, using the tenets that toxicity effects are related to the total uptake rate of the toxic metal, and that toxicity is not usually dependent on the total accumulated metal concentration but always on the concentration of accumulated metal that is metabolically available. We dismiss the general concept that there is a critical accumulated body concentration of a metal in an invertebrate at which toxicity ensues, except under specific circumstances involving a rare lack of storage detoxification of accumulated metal. We thus propose a theoretical framework that can be extended to other metals and other aquatic invertebrates (indeed other animals) to explain the variation in the relationship between bioaccumulated body concentrations and toxicity, and subsequently to predict this relationship in many other species for which we have bioaccumulation modelling data.