Toxic harm of Hg2+, Cd2+ and their combined stress on Elodea nuttallii

The influence of Hg2+, Cd2+ of different concentrations and their combined treatment on dissoluble protein concentration, chlorophyll content, chlorophyll a/b ratio, productivity and respiration of Elodea nuttallii were studied utilizing aquatic microcosm. Under low concentration stress Hg2+ [less-than or equal to] 2.5 μmol/L, Cd2+ [less-than or equal to] 10 μmol/L and Hg2+ + Cd2+ [less-than or equal to] 1.25 μmol/L Hg2+ + 5 μmol/L Cd2+, the contents of dissoluble protein and chlorophyll increased slightly; and then decreased continuously with increase of the stress with negative correlation. Chlorophyll a/b ratio, net productivity and respiration strength decreased continuously with increase of ion concentration, except respiration strength, also with negative correlation. The toxicity of Hg2+ on Elodea nuttallii was about 4 times more than that of Cd2+ (calculation with μmol/L). Under Hg2+ and Cd2+ combined actions, they revealed synergism effects on dissoluble protein and chlorophyll contents and net productivity; but addition effects on respiration.