Does the accumulation of trace metals in crustaceans affect their ecology—the amphipod example?

Abstract

Crustaceans, like all aquatic invertebrates, take up and accumulate metals from a wide range of sources and the trace metal concentrations within their tissues and bodies show great variability. Trace metal uptake in crustaceans occurs from the water and food, either of which may be affected by the physico-chemical properties of the sediment. Accumulated metal concentrations in amphipods are contrasted with those of other crustaceans and examples are given to show how external and internal factors affect bioaccumulation. One of the major pathways for the uptake of trace metals is from solution directly through permeable surfaces including the gills. Changes in salinity and oxygen tension can modify the uptake characteristics from solution particularly in the case of interstitial water within sediments. Infaunal amphipods have direct contact with the sediment and the bioavailabilities of trace metals depend on the strength of the metal binding which is determined by a combination of properties including grain size, organic content, the presence of metals such as lead and iron as well as other ambient environmental conditions. Metal concentrations within amphipod bodies reflect the bioavailabilities of trace metals in their habitat. Body size is one of the major factors contributing to individual variability in trace metal concentrations within species. For some amphipod species, there are differences in trace metal accumulation with gender, breeding and developmental stage. In amphipods, accumulated body metal concentrations are the best biomarkers for environmental metal availabilities. Metal accumulation affects the ecology of crustaceans as a consequence of the energy costs associated with excreting and/or detoxifying the incoming metals. If the costs are significant, then this may result in reduced growth and reproduction. The effects of accumulated metals on communities have yet to be determined. Accumulated metals in crustacean prey species may be transferred along the food chain, but biomagnification in fish appears unlikely. One of the main ecological challenges is the need to link molecular biomarkers with ecologically relevant life history characteristics including growth, survival, reproduction and recruitment.