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Cytochrome P450 and organochlorine contaminants in black-crowned night-herons from the Chesapeake Bay region, USA

Environmental Toxicology and Chemistry

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Abstract

Black-crowned night-heron (Nycticorax nycticorax) offspring were collected from a relatively uncontaminated coastal reference site (next to Chincoteague National Wildlife Refuge, VA, USA) and two sites in the Chesapeake Bay watershed (Baltimore Harbor, MD and Rock Creek Park, Washington, DC, USA). Hepatic microsomal activities of benzyloxyresorufin-O-dealkylase and ethoxyresorufin-O-dealkylase were significantly elevated (up to sixfold and ninefold induction, respectively) in pipping embryos from the Baltimore Harbor colony compared to the reference site, whereas values in embryos from the Rock Creek Park colony were intermediate. Concentrations of organochlorine pesticides and metabolites in pipping embryos from both sites in the Chesapeake watershed were greater than at the reference site but below the known threshold for reproductive impairment. However, concentrations of 10 arylhydrocarbon receptor-active polychlorinated biphenyl (PCB) congeners and estimated toxic equivalents were up to 37-fold greater in embryos collected from these two sites in the Chesapeake Bay region, with values for toxic congeners 77 and 126 exceeding those observed in pipping heron embryos from the Great Lakes. Monooxygenase activity of pipping embryos was associated with concentrations of several organochlorine pesticides, total PCBs, arylhydrocarbon receptor-active PCB congeners, and toxic equivalents (r = 0.30-0.59), providing further evidence of the value of cytochrome P450 as a biomarker of organic contaminant exposure. Organochlorine contaminant levels were greater in 10-d-old nestlings from Baltimore Harbor than the reference site but had no apparent effect on monooxygenase activity or growth. These findings demonstrate induction of cytochrome P450 in pipping black-crowned night-heron embryos in the Chesapeake Bay region, probably by exposure to PCB congeners of local origin, and the accumulation of organochlorine pesticides and metabolites in nestling herons from Baltimore Harbor. Biomonitoring with additional waterbird species (e.g., bald eagle, common tern, great blue heron) that appear to be more sensitive to PCBs than black-crowned night-herons is recommended to document health of waterbirds and remediation of the Chesapeake Bay.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Cytochrome P450 and organochlorine contaminants in black-crowned night-herons from the Chesapeake Bay region, USA
Series title:
Environmental Toxicology and Chemistry
Volume
16
Issue:
11
Year Published:
1997
Language:
English
Publisher:
US Dept Interior
Contributing office(s):
Upper Midwest Environmental Sciences Center
Description:
pp. 2315-2322
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Toxicology and Chemistry
First page:
2315
Last page:
2322