Interactions of trace metals and different marine food chains

Abstract

There is increasing recognition of the quantitative importance of metal accumulation from dietary pathways in different marine food webs. With a simple kinetic model requiring measurements of metal assimilation efficiency (AE), metal efflux rate and ingestion activity of the relevant animals, it is possible to predict the transfer (and potential biomagnification) of metals along diverse marine food chains. In this paper, food chain transfer in different marine food chains (planktonic and benthic) is reviewed, and any potential biomagnification of metals is predicted using the simple kinetic equation. It is well recognized that metal concentrations in animals are probably not related to the trophic level in the food chain, but some metals (Hg and Zn) may potentially be influenced by the numbers of trophic interactions involved. Depending on these different trophic interactions, the potential biomagnification of metals is influenced by metal assimilation or metal efflux rate or both. Metals may potentially be biomagnified in benthic food chains; principally, in those with gastropods as top predators, as they can efficiently sequester dietary metals. The biodiminution of metals (concentration decreases at a higher trophic level) in the classical marine planktonic food chain (phytoplankton to copepods to fish) is largely the result of the effective efflux of metals by the copepods and the very low assimilation of metals by marine fish. Although many past studies have considered the physico-chemical properties of metals in prey in controlling food chain transfer, it is suggested that the physiological and biochemical processes in the herbivore or predator should be emphasized in future studies. Also, the complicated metal-handling strategies found in different marine organisms clearly need to be appreciated.