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Tuesday "Noon" Seminar : Sept. 5

12:30-1:45 p.m. in Biosciences West (map of building location), Room 208

Talk Abstract

The fish community of Aravaipa Creek, Arizona, with seven native species, including threatened species Meda fulgida and Tiaroga cobitis, and relatively few well established exotic species, is considered the foremost remnant assemblage of the imperiled Gila River basin fauna. This study presents results from (1) high-precision isotopic analyses of lead (208Pb, 207Pb, and 206Pb) to determine levels, sources and mechanisms of deposition of lead contamination in fishes and invertebrates and (2) stable isotopes of carbon (δ13C ‰) and nitrogen (δ15N ‰) to determine trophic interactions among community members and mechanisms of bioaccumulation. Lead (Pb) has three radiogenic daughter isotopes 208Pb, 207Pb, and 206Pb that, when ratioed to each other or the one stable isotope 204Pb, provide a useful discriminator of lead contaminant sources. We find (1) very high levels of lead contamination in certain species and (2) the major source of heavy metal accumulation and transport mechanism is different from targeted remediation efforts. This novel approach, using radiogenic isotopes in biological systems, has lead to applications in other systems, such as determining sources of lead contamination in reintroduced condors (Gymnogyps californianus) at Vermilion Cliffs, Arizona. Fragments of bullets in carcasses and lead from mines or other environmental inputs have been proposed as alternative sources of lead contamination in condors. Here we use radiogenic lead isotopes to investigate potential sources of environmental lead contamination and linkages between bullet fragments and blood contamination. Specifically we compare (1) isotopic signatures of specific bullet fragments with lead in the blood and (2) lead signals in condor populations with background environmental and bullet lead signatures. We present conclusive data to support the hypothesis that bullet fragments are the source of lead poisoning in condors.