Effects of lead-contaminated sediment on Rana sphenocephala tadpoles.
We exposed larval southern leopard frogs (Rana sphenocephala) to lead-contaminated sediments to determine the lethal and sublethal effects of this metal. Tadpoles were laboratory-raised from early free-swimming stage through metamorphosis at lead concentrations of 45, 75, 180, 540, 2360, 3940, 5520, and 7580 mg/kg dry weight in sediment. Corresponding pore water lead concentrations were 123, 227, 589, 1833, 8121, 13,579, 19,038, and 24,427 microg/L. Tadpoles exposed to lead concentrations in sediment of 3940 mg/kg or higher died within 2 to 5 days of exposure. At lower concentrations, mortality through metamorphosis ranged from 3.5% at 45 mg/kg lead to 37% at 2360 mg/kg lead in sediment. The LC50 value for lead in sediment was 3728 mg/kg (95% CI = 1315 to 72,847 mg/kg), which corresponded to 12,539 microg/L lead in pore water (95% CI = 4000 to 35,200 microg/L). Early growth and development were depressed at 2,360 mg/kg lead in sediment (8100 microg/L in pore water) but differences were not evident by the time of metamorphosis. The most obvious effect of lead was its pronounced influence on skeletal development. Whereas tadpoles at 45 mg/kg lead in sediment did not display permanent abnormalities, skeletal malformations increased in frequency and severity at all higher lead concentrations. By 2360 mg/kg, 100% of surviving metamorphs displayed severe spinal problems, reduced femur and humerus lengths, deformed digits, and other bone malformations. Lead concentrations in tissues correlated positively with sediment and pore water concentrations.
Sparling
Donald W
DW
US Geological Survey, Patuxent Wildlife Research Center, Laurel, Maryland, USA. dsparl@siu.edu
Krest
Sherry
S
Ortiz-Santaliestra
Manuel
M
D000818:Animals; D000013:Congenital Abnormalities / Q000209:etiology*; D004305:Dose-Response Relationship, Drug; D019015:Geologic Sediments / Q000737:chemistry*; D007814:Larva / Q000187:drug effects / Q000378:metabolism; D007854:Lead / Q000493:pharmacokinetics / Q000633:toxicity*; D011898:Ranidae; D014018:Tissue Distribution; D018675:Toxicity Tests; D014874:Water Pollutants, Chemical / Q000493:pharmacokinetics / Q000633:toxicity*
D014874:Water Pollutants, Chemical; D007854:Lead