| Abstrakt: |
The chronic toxicity of mercury (Hg) toDaphnia magna was studied under flow-through and renewed static conditions. Concentrations of mercuric chloride (HgCl2), methyl mercuric chloride (MMC) and phenyl mercuric acetate (PMA) in flow-through tests significantly affecting survival were 1.92, between 0.26 and 0.98, and 2.25µg Hg/L, respectively. Concentrations of HgCl2, MMC, and PMA significantly impairing young production (P?0.05) were 0.72, 0.04, and 1.90µg Hg/L, respectively. Body accumulation of mercury was greatly influenced by the chemical form of mercury in the water. About nine times more mercury, added as MMC, was tolerated in daphnids at water concentrations permitting survival than was tolerated when added as HgCl2. At about the same mercury concentration in water (~0.26µg Hg/L) daphnids accumulated ~20 times more mercury when it was added as MMC than when it was added as HgCl2. Mercury was rapidly accumulated in daphnids; however, 35 and 57% of the mercury added as MMC and HgCl2, respectively, was lost when animals were placed in control water for four days following exposure. Different forms of mercury behaved quite differently in renewed-static and flow-through systems. The results also indicate the shortcomings of renewed-static tests with volatile and readily degradable compounds. |
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