Ba. Rattner et al., Organochlorine and metal contaminant exposure and effects in hatching black-crowned night herons (Nycticorax nycticorax) in Delaware Bay, ARCH ENV C, 39(1), 2000, pp. 38-45
Citations number
55
Categorie Soggetti
Environment/Ecology,"Pharmacology & Toxicology
Journal title
ARCHIVES OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY
Pea Patch Island in Delaware Bay is the site of the largest heronry north o
f Florida. From 1989-93, the popu lation of nine species of wading birds nu
mbered approximately 12,000 pairs, but has recently declined to about 7,000
pairs. Because Delaware Bay is a major shipping channel and receives anthr
opogenic releases of toxic substances from agricultural, industrial, and mu
nicipal point and nonpoint sources, contaminant exposure and effects to the
heronry have been an ongoing concern. In 1997, pipping (early hatching sta
ge) black-crowned night herons (Nycticorax nycticorax) were collected from
separate nests at Pea Patch Island and from a coastal reference site, Middl
e Island in Rehoboth Bay, Delaware. There was no evidence of malformations
or hepatic histopathological lesions in embryos, and their body and liver w
eights did not differ between sites. Biomarkers of petroleum hydrocarbons,
polyhalogenated contaminant, and metal exposure (cytochrome P450 induction
and oxidative stress responses) did not differ (p > 0.05) between sites, al
though activities of benzyloxy-O-dealkylase and ethoxyresorufin-O-dealkylas
e were somewhat elevated in 3 of the 15 embryos collected from Pea Patch Is
land. Concentrations of 21 organochlorine pesticides and metabolites were r
elatively low at both sites, with p,p'-DDE values well below the threshold
associated with eggshell thinning. Although total PCB concentration was mod
estly elevated (p < 0.05) in Pea Patch Island heron embryos, levels of aryl
hydrocarbon receptor-active PCB congeners, polychlorinated dibenzodioxins a
nd dibenzofurans, and toxic equivalents were low and did not differ between
sites. Concentrations of Cd and Mn in pipping embryos from Pea Patch Islan
d were slightly greater (p < 0.05) than values observed in Middle Island em
bryos, but levels of these and the other metals and metalloids (e.g., Hg an
d Se) were below values associated with toxicity. In conclusion, it seems u
nlikely that chlorinated hydrocarbon and metal contaminant exposure constit
utes a direct threat to the reproductive success of black-crowned night her
ons at Pea Patch Island. However, low-level exposure to these contaminants
may constitute one of many stressors that in combination could adversely af
fect the stability of the wading bird population at this large heronry.