Copper and Manganese Influence the Uptake of Cadmium in Marine Macroalgae

Of the numerous published experimental studies in aquatic ecotoxicology, by far the greatest number have been concerned with analysing the effects of, or responses to, individual contaminants. Yet, invariably, under field conditions biota are exposed to complex cocktails of chemicals. Despite mounting evidence for interactive effects amongst such mixtures, the extent to which interactions are synergistic, antagonistic or additive, with respect to uptake and toxicity has only rarely been determined. Information that is available has been derived mainly from studies on mammals (Amiard-Triquet and Amiard 1998); for example, certain trace metals can influence the uptake and/or toxicity of other metals. In such cases the major source of metals is the diet and interactions therefore occur within the organism e.g. changes in distribution, storage and excretion. For aquatic organisms, interactions might be expected to occur both internally (e.g. Robinson and Ryan 1986) and externally through, for example, alterations in metal speciation and bioavailability (e.g. Rainbow et al. 1993).