Selenium Differentially Influences Methylmercury Retention across Mayfly Life Stages.

Area of Science:

• Environmental toxicology
• Aquatic ecology
• Biogeochemistry

Background:

• High concentrations of mercury and selenium are toxic individually.
• A hypothesized antagonistic relationship exists between mercury and selenium.
• This interaction is under-studied in aquatic macroinvertebrates and complex life histories.

Purpose of the Study:

• To examine the effect of selenium on methylmercury accumulation in mayflies across four life stages.
• To investigate the mercury-selenium interaction in aquatic macroinvertebrates.

Main Methods:

• Mayflies (Neocloeon triangulifer) were exposed to elevated methylmercury via diatoms and aqueous selenomethionine.
• Methylmercury accumulation was measured across four life stages.
• Life history transfer factor (LHTF) was calculated.

Main Results:

• Selenium reduced methylmercury accumulation in high methylmercury environments but not in low methylmercury environments.
• Terrestrial adult mayflies had higher mercury concentrations than aquatic larval stages.
• Life history transfer factor varied with selenium exposure, suggesting complex interactions.

Conclusions:

• The mercury-selenium antagonism is context-specific, particularly in high methylmercury environments.
• Selenium's interference with methylmercury accumulation is dependent on environmental mercury levels.
• Predators consuming adult aquatic insects face higher methylmercury exposure than those consuming larvae.