THE INFLUENCE OF PH AND MEDIA COMPOSITION ON THE UPTAKE OF INORGANIC SELENIUM BY CHLAMYDOMONAS-REINHARDTII

The uptake of inorganic selenium species, selenate and selenite, by th e green alga Chlamydomonas reinhardtii Dang was examined as a function of pH over the range 5 to 9 and in media with varying concentrations of major ions and nutrients using Se-75 as a radiotracer. Little diffe rence was noted in the uptake of selenate as a function of pH, with th e maximum uptake occurring at pH 8; however, selenite uptake increased substantially at the lower pH values. Selenate uptake was significant ly decreased by higher sulfate concentrations and increased significan tly by calcium, magnesium, and ammonium. Selenite uptake was significa ntly increased when the phosphate concentrations in the media were red uced. The results of these experiments demonstrate that varying water chemistry may significantly affect the uptake of inorganic selenium by phytoplankton and the subsequent transfer of the selenium to higher t rophic levels.