Mercury Contamination in Free-Ranging Great Egret Nestlings (Ardea Albus) From Southern Florida, Usa

Abstract

Between March and June of 1994 and 1995, mercury (Hg) concentrations were determined from 393 blood and 164 growing scapular feathers from 252 great egret nestlings (Ardea albus). Nestlings came from eight colonies located in Water Conservation Area 3 in the Everglades region in southern Florida. The ages of these birds ranged from 1 to 44 d (bill length 1.1 to 10.2 cm). Mercury concentrations in blood and feathers of first-hatched great egret nestlings sampled during 1994 averaged 1.2 g/g (range ϭ 0.07-3.9) wet weight and 16 g/g (4.5-40) dry weight, respectively. During 1995, first-hatched chicks had blood and feather Hg concentrations that averaged 0.8 g/g (0.2-1.7) and 9.7 g/g (2.3-26), respectively. In both years, Hg concentrations in blood and feathers were significantly correlated, and a significant correlation also was found between Hg in blood and age of the chicks. Blood and feather Hg concentrations differed significantly between years, with higher concentrations during 1994. Birds from JW1 and L67 colonies had the highest concentrations of Hg in blood and feathers. Mercury concentrations did not differ between chicks of different hatch order. Mercury in feathers of great egret nestlings from southern Florida are approximately six times higher when compared to feather Hg concentrations of nestling wading birds sampled elsewhere.

Contamination and Biomarkers in the Great Blue Heron, an Indicator of the State of the St. Lawrence River

“…Despite this decline, Hg levels in eggs were still higher or comparable to other published levels for great blue heron eggs from various locations in North America (Elliott et al, 1989;Custer et al, 1997;Thomas and Anthony, 1999). Mercury levels in blood were also high compared to other published data for nestlings of various piscivorous species (Sepuvelda et al, 1999). Few studies provide information on threshold impacts of Hg levels in blood of birds.…”

“…Wolfe and Norman (1998) reported levels of 1.2 lg/g w.w. in apparently successful heron colonies. Hg levels in feathers of herons from this study appear high compared with other published data on herons (Wolfe and Norman, 1998;Sepuvelda et al, 1999;Goutner et al, 2001). Sampling of various types of feathers in these studies could explain part of these differences.…”

Subchronic effects of methylmercury on plasma and organ biochemistries in great egret nestlings

“…Methylmercury has been well-documented as a contaminant that bioaccumulates in aquatic ecosystems and has been linked to adverse effects in top carnivores [1][2][3][4][5][6][7][8][9][10]. Methylmercury has been suggested as one of the possible causes for reduced reproduction of long-legged wading birds (Ciconiiformes) in the Florida Everglades, USA, in recent decades [11][12][13][14][15][16].…”

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

“…The Everglades of southern Florida is an ecosystem in which the biota had become highly contaminated with Hg by the 1990s, and a number of detrimental effects on biota and potential threats to human health have been documented [4,[8][9][10][11]. Between 1994 and 1998, however, a decrease of Ͼ74% in total Hg was detected using feathers of nestling great egrets (Ardea alba) collected annually in a standardized fashion [12]; similar trends have been found using largemouth bass (Micropterus salmoides) fillets [13].…”