Selenium pollution in the marine environment and marine bacteria in selenium bioremediation

Abstract

Selenium (Se), a metalloid, is a micronutrient essential to biological systems at lower concentrations but becomes toxic as the level increases. Among the soluble forms of Se, selenite is more toxic than selenate to most living organisms. Selenium pollution is a global phenomenon and is associated with a wide range of human activities, from basic agricultural practices to the modern industrial processes that increase the threat of widespread impacts to aquatic life. Soluble forms of selenium, being mobile, reach groundwaters, whereas other static forms remain in soils. Aquatic organisms living in waters contaminated with Se or wildlife consuming plants from selenium-rich soils may be harmed as they accumulate a level of selenium higher than required by their bodies. Although selenium may prove very risky, resulting in long-term serious effects on aquatic life and fishery resources, selenium contamination in the aquatic environment often goes unnoticed by environmental biologists. The permissible level of total selenium in the aquatic environment is about 2 µg/l. To avoid adverse effects on marine aquatic life, the drainage water should be treated to minimize selenium content before it flows into rivers. The conventional physicochemical methods employed in selenium removal, although effective, may prove to be quite expensive. Recent studies suggest the use of microbiological resources to detoxify selenium to be the most simple and economical method. Science is advancing with newer approaches to tackle this problem of selenium pollution.