Mercury contamination in free‐ranging great egret nestlings (Ardea albus) from Southern Florida, USA

Abstract

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.

Histologic, Neurologic, and Immunologic Effects of Methylmercury in Captive Great Egrets

“…GWH ϭ great white heron, GBH ϭ great blue heron. c Source: A ϭ Wolfe and Norman, 1998; B ϭ Sepulveda et al, 1999a;C ϭ Sundlof et al, 1994;D ϭ Spalding et al, 1994;E ϭ Williams, 1997;F ϭ Sepulveda, 1999b;G ϭ Spalding, unpubl. data. great white herons at Ͼ3 mg/kg and Sepulveda et al (1999b) noted a trend toward decline in lymphocyte numbers at 5 mg/kg.…”

Physiological Condition of Juvenile Wading Birds in Relation to Multiple Landscape Stressors in the Florida Everglades: Effects of Hydrology, Prey Availability, and Mercury Bioaccumulation

“…Current Hg exposure levels of egrets and ibises throughout much of the Florida Everglades are low relative to historical reports [28], [68]. However, the fact that for egrets, one of their HSPs was influenced by Hg, demonstrates that the current Hg levels could still influence the physiology of this species.…”

A Screening Level Probabilistic Risk Assessment of Mercury in Florida Everglades Food Webs

“…Great egrets in southern Florida contain elevated Hg (e.g., 0.18-4.3 ppm wet weight in liver) (Beyer et al, 1997;Sundlof et al, 1994), and may be experiencing impaired reproductive success and reduced population levels from Hg exposure Sepulveda et al, 1999). Adult great egrets typically weigh about 1-2 kg and eat 0.18-0.42 kg/day of primarily larger fish and other aquatic biota (Lodge, 1994;Hancock and Elliot, 1984;Spector, 1956;Palmer, 1962;U.S.…”

“…Hg concentrations in invertebrates ranged from 0.00005 ppm in the northern Everglades 300 Jurczyk, 1993;Whitaker and Hamilton, 1998;Palmer, 1975;Spector, 1956;U.S. EPA, 1993;Stuewer, 1943;Palmer, 1954;Kaufmann, 1982 Median Jurczyk, 1993;Hancock and Elliot, 1984;Spector, 1956;Sepulveda et al, 1999;Palmer, 1962 to 0.06 ppm in the southern parts of WCA 2 (Cleckner et al, 1998). Royals and Lange (1990) reported low levels of mercury in crayfish from the Everglades but did not specify concentrations.…”