Chemical and biological aspects of metal availability to the brine shrimp Artemia franciscana

The biological availability of metals (i.e. Cu and Cd) to the brine shrimp depends on the speciation of the metal in the environment and the functional characteristics of the interface which separates solution and organism. To explain the effects of changes in environmental conditions on the biological availability of metals it is necessary to consider the speciation of the metal and the functionality of the solution-organism interface simultaneously. Metal availability is related to the activity of the free metal ion in the solution which is determined by the ionic strength and complexation capacity of the solution. The effect of complexation on metal uptake does not depend on the thermodynamic stability of the complexes formed. Changes in ionic strength and other environmental factors also alter the flux of metals across the solution-body interface. Considering the speciation of the metal in the solution and the effects of the environment on the physiological organisation of the solution-body interface can explain most of the variation in metal uptake under a wide variety of conditions.