title: Distribution and accumulation of mercury in tissues of captive-reared common loon (Gavia immer) chicks.
abstract: We determined the distribution and accumulation of Hg in tissues of common loon (Gavia immer) chicks maintained for up to 15 weeks on either a control diet with no added methylmercury chloride (MeHgCl) or one containing either 0.4 or 1.2 microg Hg (as MeHgCl)/g wet-weight food. Total Hg and MeHg tissue concentrations were strongly positively correlated (r2 > 0.95) with the amount of Hg delivered to individual chicks throughout the course of the experiment. The pattern of differential Hg concentration in internal tissues was consistent within each treatment: Liver > kidney > muscle > carcass > brain. Feather Hg concentrations were consistently higher than those of internal tissues and represented an important route of Hg elimination. Feather mass accounted for 4.3% +/- 0.1% (average +/- standard error) of body mass, yet 27.3% +/- 2.6% of total Hg intake was excreted into feathers. Our calculations indicate that 26.7% +/- 4.9% of ingested Hg was not accounted for and, thus, either was never absorbed or was absorbed and subsequently eliminated in feces. With the additional excretion into feathers, 54% of ingested Hg was excreted. Demethylation was evident in the liver at all treatment levels and in the kidneys of chicks dosed at 1.2 microg Hg/g. Mercury concentrations were strongly positively correlated (r2 > or = 0.95) among internal tissues and with blood Hg concentration. Mercury concentrations of secondary feathers were moderately correlated (r2 = 0.82-0.93) with internal tissues. We supply regression models that may be used to provide perspective and a useful means of interpreting the variety of measures of Hg exposure reported in the literature.
authors.affiliation: U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, Wisconsin 54603, USA. kkenow@usgs.gov
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Kenow
authors.forename: Michael W
authors.initials: MW
authors.lastname: Meyer
authors.forename: Randy K
authors.initials: RK
authors.lastname: Hines
authors.forename: William H
authors.initials: WH
authors.lastname: Karasov
mesh_terms: D000818:Animals; D001717:Birds / Q000378:metabolism*; D001835:Body Weight / Q000187:drug effects* / Q000502:physiology; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism / Q000633:toxicity; D005241:Feathers / Q000187:drug effects* / Q000502:physiology; D005243:Feces / Q000737:chemistry; D008628:Mercury / Q000032:analysis / Q000378:metabolism / Q000633:toxicity; D008767:Methylmercury Compounds / Q000032:analysis / Q000378:metabolism / Q000633:toxicity; D012044:Regression Analysis; D014018:Tissue Distribution / Q000187:drug effects* / Q000502:physiology
chemical_list: D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D008628:Mercury