title: Field exposure of frog embryos and tadpoles along a pollution gradient in the Fox River and Green Bay ecosystem in Wisconsin, Usa.
abstract: We raised embryos and tadpoles of green frogs (Rana clamitans melanota) and leopard frogs (R. pipiens) in situ along a contamination gradient in the Fox River/Green Bay ecosystem (WI, USA). Differences in exposure were reflected by significant positive regressions between concentrations in sediment and in frogs of polychlorinated biphenyl (PCB) congeners and some heavy metals (Cd, Cr, and Pb), which could have predictive value for estimating exposure of amphibians to contaminants in this ecosystem and, perhaps, in others. On average, non-ortho-substituted coplanar PCBs made up a very small percentage (average, 0.2%) of the PCB congeners in all samples analyzed, with larger fractions accounted for by mono- and di-ortho congeners (average, 19%) and routine congeners (average, 81%). Hatchability of frog embryo batches and anuran species richness at the sites were negatively correlated with level of contamination, but tadpole growth and survival were not. Sediment and tissue levels of PCBs and metals generally were correlated with each other, confounding the association of effects on frogs with any particular contaminant. It is also plausible that high levels of un-ionized ammonia (NH3) reduced hatching success of green frog, but not leopard frog, embryos in the field enclosures. Other environmental factors that were present but unmeasured in the field, such as ultraviolet-B radiation as well as water flow and level fluctuations, might have caused differences in hatching success at the field sites.
authors.affiliation: Department of Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. wkarasov@wisc.edu
authors.forename: William H
authors.initials: WH
authors.lastname: Karasov
authors.forename: Robin E
authors.initials: RE
authors.lastname: Jung
authors.forename: Susan Vanden
authors.initials: SV
authors.lastname: Langenberg
authors.forename: Tara L E
authors.initials: TL
authors.lastname: Bergeson
mesh_terms: D000818:Animals; D017753:Ecosystem; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis / Q000633:toxicity; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000633:toxicity; D011898:Ranidae / Q000196:embryology / Q000254:growth & development*; D045483:Rivers / Q000737:chemistry*; D013997:Time Factors; D014018:Tissue Distribution; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*; D014922:Wisconsin
chemical_list: D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls