Selenium Bioaccumulation in Freshwater Organisms and Antagonistic Effect against Mercury Assimilation

Abstract

We present evidence of selenium bioaccumulation at lower levels of the aquatic food chain and its antagonistic effect against mercury and methyl mercury assimilation in the aquatic food web. Most of our studies were carried out in freshwater lakes of the mining region of Sudbury, Ontario, Canada where the presence of metal smelters has introduced elevated levels of selenium in the surrounding terrestrial and aquatic ecosystems. The studies with different types of aquatic organisms demonstrate a consistent inverse relationship between concentrations of mercury/methyl mercury and selenium in whole bodies (zooplankton, benthic invertebrates, mayflies and amphipods, beetle larvae and newly hatched perch) or in muscle, liver and brain (perch and walleye). This antagonistic effect was also observed in laboratory controlled experiments with the incubated soil and surface water bacterium Pseudomonas fluorescens. We also present some information on Se accumulation at different levels of the food web with samples collected in the past years in order to provide an insight for estimating the potential risk of selenium bioaccumulation and its possible detrimental consequence on aquatic ecosystems. Selenium could be considered as an indicator of susceptibility of fish to Hg toxicity.

Keywords:

• selenium
• mercury
• bioaccumulation
• antagonism
• aquatic organisms

Acknowledgements

Our research is supported by the Natural Sciences and Engineering Council of Canada and by the Ontario Ministry of Natural Resources through support of the staff of the Cooperative Freshwater Ecology Unit at Laurentian University. The manuscript benefitted from the comments of Nick Ralston and two anonymous reviewers.