title: Effects of lead-contaminated sediment on Rana sphenocephala tadpoles.
abstract: 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.
authors.affiliation: US Geological Survey, Patuxent Wildlife Research Center, Laurel, Maryland, USA. dsparl@siu.edu
authors.forename: Donald W
authors.initials: DW
authors.lastname: Sparling
authors.forename: Sherry
authors.initials: S
authors.lastname: Krest
authors.forename: Manuel
authors.initials: M
authors.lastname: Ortiz-Santaliestra
mesh_terms: 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*
chemical_list: D014874:Water Pollutants, Chemical; D007854:Lead