A historical record of mercury contamination in southern florida (USA) as inferred from avian feather tissue: Contribution R‐09888 of the Journal Series, Florida Agricultural Experiment Station

Abstract

During the late 1980s, the upper trophic-level biota of the Everglades (FL, USA) was recognized as being highly contaminated with mercury (Hg). However, the timing and pattern of that increase is poorly known, and no information is available about mercury contamination in Everglades wildlife prior to 1974. We measured methylmercury concentrations in feathers of white ibises (n = 33), great egrets (n = 7), anhingas (n = 21), and great blue herons (n = 12) from museum specimens collected from 1910 through 1980 and combined them with more recent feather samples collected from live birds (1985-2000, n = 98, 37, 49, and 7, respectively). We found no evidence of contamination of museum samples with inorganic mercuric preservatives (0.01-0.28% of total Hg in feathers). All species showed relatively low concentrations of mercury through the 1970s (<5 microl/L dry wt for anhingas, ibises, and egrets, <10 microl/L for herons). Samples from all species taken during the 1990s showed a large and significant increase (4-5X) in MeHg concentration. This evidence suggests that most of the increase in Hg deposition during the 20th century in south Florida occurred during the last two to three decades, which is consistent with information about local source deposition. Contamination levels prior to the 1970s appear to have been associated with normal reproduction in these birds, suggesting partial evidence for a threshold of reproductive impairment.

Patterns and Interpretation of Mercury Exposure in Freshwater Avian Communities in Northeastern North America

“…Virtually all Hg in a feather is MeHg (Thompson and Furness, 1989) and is sequestered for long time periods allowing retrospective analysis (Frederick et al, 2004). Feather Hg reflects blood Hg levels at the time of molt (Bearhop et al, 2000), however, if MeHg is depurated in the muscle tissue (as is the case for individual birds with a high dietary MeHg uptake), it is available for remobilization.…”

Avian Resources of the Northern Gulf of Mexico

“…Comparisons of museum specimens of feathers from wading birds nesting in the Everglades from 1920 to the 1970s indicated that samples taken during the 1990s had mercury levels that were 4-5 times higher than feathers from specimens collected before 1970 (Frederick et al 2004), indicating an anthropogenic source. Fish-eating birds are particularly vulnerable to the effects of methylmercury because it accumulates in fish.…”

“…Fish-eating birds are particularly vulnerable to the effects of methylmercury because it accumulates in fish. Birds that eat large fish with the highest mercury levels are most at risk (Pinho et al 2002;Storelli et al 2002;Burger 2009;Burger et al , 2011Frederick et al 1999Frederick et al , 2004. Common Loons Burgess et al 2005;Burgess and Meyer 2008;Evers et al 2008), raptors (Albers et al 2007), and songbirds (Jackson et al 2011) are species with high mercury levels that have impaired reproduction, with possible population declines.…”

Piscivorous Mammalian Wildlife as Sentinels of Methylmercury Exposure and Neurotoxicity in Humans

“…Several researchers have successfully used avian feathers to establish long-term trends in mercury pollution across the world, including focused studies in the North Atlantic Ocean (Thompson et al 1992 ) , Arctic (Dietz et al 2006a ) , Florida (Frederick et al 2004 ) , and Michigan (Head et al 2011 ) . For mammals, Dietz et al ( 2006bDietz et al ( , 2011 obtained Greenlandic polar bear fur samples from museums and Inuit collections, and documented that mercury levels in these samples have increased more than 14-fold (with an upper estimate of 27-fold) since preindustrial (1300 ad ) times.…”