HR: 09:45h
AN: B31A-06    [Abstracts]
TI: Biogeochemistry of Metals in Periodic Cicada
AU: * Robinson, G R
EM: grobinso@usgs.gov
AF: U.S. Geological Survey, 954 National Center, Reston, VA 20192 United States
AU: Sibrell, P L
EM: philip_sibrell@usgs.gov
AF: U.S. Geological Survey, 11649 Leetown Road, Kearneysville, WV 25430 United States
AU: Boughton, C J
EM: cboughton@usgs.gov
AF: U.S. Geological Survey, 11649 Leetown Road, Kearneysville, WV 25430 United States
AU: Yang, L H
EM: lhyang@ucdavis.edu
AF: University of California, Center for Population Biology, Evolution and Ecology Section, One Shields Avenue, Davis, CA 95616 United States
AU: Hancock, T C
EM: thancock@usgs.gov
AF: U.S. Geological Survey, 1730 East Parham Road, Richmond, VA 23228 United States
AB: Metal concentrations were measured in three species of 17-year periodic cicadas (Magicicada spp.) to determine the bioavailability of metals from both uncontaminated and lead-arsenate-pesticide contaminated soils and evaluate whether these metal concentrations might threaten wildlife. Collections were made in Clarke and Frederick Counties, Virginia and Berkeley and Jefferson Counties, West Virginia during Brood X emergence in May and June 2004. Periodic cicadas emerge synchronously at high density after 13 or 17 years of underground development, feeding on xylem fluids, and molt into their adult form leaving a keratin exoskeleton shell. They are an important food source for birds and animals during emergence events, and influence nutrient cycles in woodland settings. Soil concentrations at the collection sites vary over one order of magnitude for Co, Cu, Fe, Hg, Mn, Mo, Se, and Zn and over two orders of magnitude for As, Au, and Pb. The concentration levels of metals in adult periodic cicadas do not pose a dietary threat to birds and other wildlife that preferentially feed upon cicadas during emergence events. The adult cicadas contain concentrations of metals similar to, or less than, other invertebrates, such as earthworms. Average adult cicada body concentrations for As, Cu, Hg, Pb, and Zn are 3, 64, 0.015, 0.4, and 160 mg/Kg (dry weight), respectively. Much of the cicada nymph body load of metals is partitioned into the molt exoskeleton. Elements, such as Al, Fe, and Pb, are strongly enriched in the exoskeleton relative to the adult body; Cu and Zn are enriched in bodies. Concentrations of Fe, Co, and Pb, when normalized to inert soil constituents such as aluminum and cerium, are similar between the molt exoskeleton and their host soil, implying that passive assimilation through prolonged soil contact (adhesion or adsorption) may control these metal concentrations. Normalized concentrations of bioessential elements, such as S, P, K, Ca, Mn, Cu, Zn, and Mo, and chalcophile (sulfur-loving) elements, such as As, Se, and Au, show strong enrichment in cicada tissues relative to soil, implying selective absorption by xylem fluids and/or cicada nymph during development. Chalcophile elements, such as As and heavy metals, accumulate in keratin-rich tissues and may bind to sulfhydryl groups. Metal concentrations in exoskeleton show a positive correlation with soil metal concentrations. Metal concentrations in adult bodies do not correlate with soil chemistry, but bioessential elements S, Mn, Fe, and Zn show differences by sex and Cu and Zn by species.
DE: 0400 Biogeosciences
DE: 1065 Trace elements (3670)
SC: Biogeosciences [B]
MN: 2005 Joint Assembly