Trace metal uptake rates in crustaceans (amphipods and crabs) from coastalsites in NW Europe differentially enriched with trace metals

This study set out to investigate the possible effect of life history strat egy on the trace metal biology of crustaceans living in coastal sites conta minated by high availabilities of toxic metals. Amphipods brood their young , parents and offspring staying in the same habitat. Therefore a population of amphipods living in a trace-metal-rich estuary would have been selected over generations for any physiological adaptation reducing the potential t oxic action of the trace metals, such as reduced rates of uptake of metals from solution. Crabs, on the other hand, are dispersed by a planktonic larv al phase, the zoea, increasing the probability that the parents of individu als inhabiting a metal-rich estuary would have lived in a remote location n ot exposed to selection pressure to reduce metal uptake rates. Uptake rates of the dissolved trace metals Zn, Cd and Ag were, therefore, measured in a mphipods Orchestia gammarellus and crabs Carcinus maenas and Pachygrapsus m armoratus from coastal sites in Britain and France exposed to different deg rees of trace metal enrichment, in order to test 3 hypotheses: (1) the mean metal uptake rates of amphipods and crabs from a metal-rich site would be lower than those of the same crustaceans from a control site; (2) the mean metal uptake rates of amphipods would show a greater reduction from those o f control amphipods than would those of equivalent crabs; (3) the mean meta l uptake rates of amphipods from metal-rich sites would show smaller coeffi cients of variation than those of equivalent crabs. In practice the mean me tal uptake rates of both amphipods and crabs did not show consistent signif icant differences between the crustaceans from the metal-rich and control s ites. Furthermore there was no evidence to conclude that the coefficients o f variation of the mean uptake rates of amphipods from the relatively metal -rich sites are lower than those of crabs from the same sites. It is conclu ded that the exposure of the crustaceans to raised trace metal availabiliti es has not been sufficient to select for a reduction in dissolved trace met al uptake rates, even in the case of the in situ populations of amphipods. It is relevant that a suite of physiological mechanisms for the amelioratio n of the potential toxic effects of trace metals is available to coastal in vertebrates, and it remains possible that other physiological processes pro moting metal tolerance may be active to differing degrees in crustaceans fr om metal-rich habitats.