Cytochrome P450‐associated monooxygenase activities and cytochrome P450 proteins were measured in pipping black‐crowned night heron (Nycticorax nycticorax) embryos collected from a reference site (next to the Chincoteague National Wildlife Refuge, VA) and three polluted sites (Cat Island, Green Bay, Lake Michigan, WI; Bair Island, San Francisco Bay, CA; West Marin Island, San Francisco Bay, CA). In a laboratory study, artificially incubated night heron embryos from the reference site were treated with 3‐methylcholanthrene (200 μg administered into the air cell 2 d before pipping) or phenobarbital (2 mg daily for 2 d before pipping). Compared to controls (untreated + vehicle‐treated embryos), 3‐methylcholanthrene induced a greater than fivefold increase in activities of several monooxygenases (arylhydrocarbon hydroxylase, AHH; benzyloxyresorufin‐O‐dealkylase, BROD; ethoxyresorufin‐O‐dealkylase, EROD; pentoxyresorufin‐O‐dealkylase, PROD) and a greater than 100‐fold increase in the concentration of immunodetected cytochrome P450 1A (CYP1A). Phenobarbital treatment resulted in only a slight increase in BROD activity but induced proteins recognized by antibodies to cytochrome P450 2B (CYP2B) by 2,000‐fold. In a field study, activities of AHH, BROD, EROD, and ethoxycoumarin‐O‐dealkylase (ECOD) were up to 85‐fold higher in pipping black‐crowned night herons collected from Cat Island compared to other sites. Hepatic CYP1A and CYP2B cross‐reactive proteins were detected in significantly more individuals from Cat Island than from the reference site. Greatest burdens of total PCBs and p,p′‐DDE were detected in embryos from Cat Island. Cytochrome P450‐associated monooxygenase activities and cytochrome P450 proteins (AHH, BROD, EROD, ECOD, CYP1A, CYP2B) were significantly associated with total PCB burdens (r = 0.50‐0.72). These data indicate that cytochrome P450 may be a useful biomarker of exposure to some PCB mixtures in black‐crowned night heron embryos.

This study was conducted to determine selenium (Se) concentrations in tissues of birds collected during the 1983-1985 nesting seasons at Kesterson Reservoir (an area receiving high-Se irrigation drainage water), compare them with birds from reference sites within California's Central Valley, and relate them to food-chain Se concentrations at the study sites. Within years, Se in livers of adult birds collected early and late in the nesting season changed significantly at both Kesterson and the primary reference site (Volta Wildlife Area). These changes were related to the length of time birds had been present at the study sites and the associated accumulation (at Kesterson) or depuration (at Volta) of Se. All species showed significant location differences, which were greatest in species that occurred at Kesterson throughout the year or fed more consistently within the reservoir. There were few species differences in Se for birds at the reference sites (where food-chain Se levels were "normal" [less than or equal to 2 micrograms/g, dry wt]). At Kesterson (where bird foods generally contained greater than 50 micrograms Se/g), species patterns varied by year, probably because of varying periods of residence and other factors. Se concentrations in kidneys and livers of American coots (Fulica americana) were significantly correlated (r = 0.9845); Se concentrations in breast muscles and livers of juvenile ducks (Anas spp.) also were correlated (r = 0.8280). Body weights of adult coots were negatively correlated with liver Se concentration. Late-season resident breeding birds or pre-fledging juvenile birds reared at a site usually provided the best indication of site-specific Se bioaccumulation.

No abstract

During 1983-1985, we studied the reproductive success of several species of aquatic birds (coots, ducks, shorebirds, and grebes) nesting at two sites in Merced County, California: a selenium-contaminated site (Kesterson Reservoir) and a nearby reference site (Volta Wildlife Area). We used a computer program (MICROMORT) developed for the analysis of radiotelemetry data (Heisey and Fuller 1985) to estimate nest success and causespecific failure rates, and then compared these parameters and hatchability between sites and among years.Nest success and causes of failure varied by species, site, and year. The most important causes of nest failure were usually predation, desertion, and water-level changes. However, embryotoxicosis (mortality, deformity, and lack of embryonic development) was the most important cause of nest failure in Eared Grebes (Podiceps nigricollis) at Kesterson Reservoir. Embryotoxicosis also reduced the hatchability of eggs of all other species at Kesterson in one or more years; embryonic mortality occurred rarely at Volta, and abnormalities were not observed.

We collected two species of crayfish, Pacifastacus leniusculus and Procambarus clarkii, from Cache and Putah Creeks, California, and analyzed them for mercury and trace elements. Trace elements were higher in carcasses in 40 cases, higher in tails in 5 cases, and not different in 35 cases; no concentration exceeded levels considered harmful. Mercury concentrations were similar among sites, with no overall sex or species effect in tails. Mercury and methylmercury concentrations were higher in tails at all sites. Methylmercury concentrations in crayfish tails (0.156-0.256 microg/g) exceeded concentrations reported in health advisories for consumption of fish and crayfish from these watersheds.