Selenium Bioaccumulation in Freshwater Organisms and Antagonistic Effect against Mercury Assimilation

摘要

We present evidence of selenium bioaccumulation at lower levels of the aquatic foodchain and its antagonistic effect against mercury and methyl mercury assimilation inthe aquatic food web. Most of our studies were carried out in freshwater lakes of themining region of Sudbury, Ontario, Canada where the presence of metal smelters hasintroduced elevated levels of selenium in the surrounding terrestrial and aquatic eco-systems. The studies with different types of aquatic organisms demonstrate a consistentinverse relationship between concentrations of mercury/methyl mercury and seleniumin whole bodies (zooplankton, benthic invertebrates, mayflies and amphipods, beetlelarvae and newly hatched perch) or in muscle, liver and brain (perch and walleye).This antagonistic effect was also observed in laboratory controlled experiments withthe incubated soil and surface water bacterium Pseudomonas fluorescens. We alsopresent some information on Se accumulation at different levels of the food web withsamples collected in the past years in order to provide an insight for estimating thepotential risk of selenium bioaccumulation and its possible detrimental consequenceon aquatic ecosystems. Selenium could be considered as an indicator of susceptibilityoffish to Hg toxicity.