Survival of <i>daphnia magna</i> and <i>hyalella azteca</i> in cadmium-spiked water and sediment

Abstract

Abstract Freshwater sediments and water were spiked with cadmium in the laboratory, and toxicity tests were conducted with the cladoceran Daphnia magna and the amphipod Hyalella azteca to determine if Cd in the sediment would cause increased toxicity. The 48-h LC50 values for Daphnia in tests without sediment were 36, 33, 24 and 40 μg/L total Cd. Calculated free ion (Cd2+) LC50 values for the same tests were 28, 25, 18 and 31 μg/L. LC50 values (48-h) determined for total Cd (uncentrifuged water sample) in the sediment-containing beakers were 252, 69 and 122 μg/L for Daphnia. LC50 values for dissolved Cd (centrifuged 10,000 rpm) in the sediment-containing beakers were 61, 27 and 100 μg/L for Daphnia. Higher total Cd LC50 values indicate that Cd adsorbed to soluble organic material was not biologically available. The 96-h LC50 value in tests without sediment for Hyalella was 8 μg/L total Cd; two 10-d LC50 values were less than 2.8 and 6.0 μg/L. LC50 values (96-h) determined for Hyalella for total and dissolved Cd in tests with sediment were 74 and 6.6 μg/L, respectively; the 10-d LC50 for total Cd in tests with sediment was 80 μg/L. No significant mortality of Daphnia or Hyalella occurred in the flow-through tests in which sediment contained the same levels of Cd as in the static tests. Mortality was similar in beakers with and without Cd-spiked sediment, indicating that Cd in the sediment and adsorbed to organic materials was not available to cause increased mortality.