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Roger L. Hothem - One of the best experts on this subject based on the ideXlab platform.
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Reproductive Success of Black-Crowned Night-Herons (Nycticorax nycticorax) at Alcatraz Island, San Francisco Bay, California, 1990-2002
2020Co-Authors: Roger L. HothemAbstract:? Nesting chronology, habitat use, subcolony use, and hatchability were documented for Blackcrowned Night-Herons (Nycticorax nycticorax) nesting at Alcatraz Island during 1990-2002. Reproductive success was estimated using the Mayfield method and compared among years. Totals of monitored nests per year ranged from 68 in 2001 to 341 in 1996, with a trend toward declining numbers since 1996. A trend of increasing numbers of nests of Western Gulls, the primary competitor with the Black-Crowned Night-Herons, was identified during the same period. Calculated nest success has generally declined since 1994, with success less than the 13-year average of 63.9% each of the last six years. Although fledging success declined to its nadir in 1997, the 13-year average was 87.6%, and the rate has generally increased during the past 5 years. The net result, however, has been that the overall reproductive success of Black-Crowned NightHerons at Alcatraz Island has been below the 13-year average of 56.3% since 1996. During the study, the average number of chicks fledged per nest ranged from 0.46 to 1.27 chicks per monitored nest, far below the required two chicks per nest required for a sustained population. Embryos in 5 of the 187 failed Blackcrowned Night-Heron eggs that were examined contained deformed embryos. In 1990 and 1991 eggs were analyzed for a wide range of contaminants, but none appeared to be sufficiently elevated to have caused the observed deformities. Based on these relatively low levels of contaminants, a high hatchability rate (94.5%), and relatively low levels of embryotoxicity, contaminants did not appear to significantly affect Black-Crowned Night-Heron reproduction at Alcatraz Island. However, predation by Common Ravens (Corvus corax) and Western Gulls (Larus occidentalis), interspecific competition with the Western Gulls, habitat deterioration, and possible human disturbance are likely factors contributing to the decline in Black-Crowned Night-Heron reproduction on Alcatraz Island in recent years. Studies conducted in the early 1980s suggested that environmental contaminants were adversely affecting reproduction by Black-Crowned Night-Herons (Nycticorax nycticorax) nesting in South San Francisco Bay (Ohlendorf et al. 1988; Hoffman et al. 1986). A project designed to evaluate the effects of contaminants on the reproductive success of Black-Crowned Night-Herons and Snowy Egrets (Egretta thula) nesting in San Francisco Bay was initiated in 1989 and included Alcatraz Island beginning in 1990 (Hothem et al. 1995). Black-Crowned Night-Herons had nested on Alcatraz Island since at least the early 1980s, with estimates of total nests ranging from 24 in 1981 (Boarman 1989) to about 60 in 1989 (M. Alvarez and T. Thomas, Golden Gate National Recreation Area, unpubl. data). Although gross numbers of nests had been estimated sporadically, neither the reproductive success of the colony nor the potential adverse impacts of environmental contaminants on reproduction had been estimated. In addition, to facilitate the conservation of nesting birds on Alcatraz, the National Park Service (NPS) needed data on nesting, hatching, and fledging success of Black-Crowned Night-Herons to facilitate their planning for increased visitor access to the island. In 2002, we monitored Black-Crowned Night-Heron reproduction at Alcatraz for the thirteenth consecutive year. METHODS Study Area The study site was Alcatraz Island (37 49’ N, 122 25’ W), a National Historic Landmark within the Golden Gate National Recreation Area. This 9.1-ha island, in the central portion of San Francisco Bay, about
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Reproductive Success of the Black-Crowned Night Heron at Alcatraz Island, San Francisco Bay, California, 1990-2002
Waterbirds, 2004Co-Authors: Roger L. Hothem, Daphne HatchAbstract:Abstract Nesting chronology, habitat use, subcolony use, and hatchability were documented for the Black-Crowned Night Heron (Nycticorax nycticorax) nesting at Alcatraz Island, San Francisco Bay, California during 1990-2002. Reproductive success was estimated using the Mayfield method and compared among years. Totals of monitored nests per year ranged from 68 in 2001 to 341 in 1996, with a trend of declining numbers since 1996. An increase in numbers of the Western Gull (Larus occidentalis), the Black-Crowned Night Heron’s primary competitor, occurred during the same period. Overall reproductive success of the Black-Crowned Night Heron at Alcatraz Island was below the 13-year average of 56.4% since 1996. During the study, the average number of chicks fledged per nest each year ranged from 0.46 to 1.27, which is less than the two chicks per nest suggested as a requirement for a sustained population. Embryos in five of 187 failed Black-Crowned Night Heron eggs were deformed. In 1990 and 1991, eggs were analy...
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Biomonitoring environmental contamination with pipping black‐crowned Night Heron embryos: Induction of cytochrome P450
Environmental Toxicology and Chemistry, 1993Co-Authors: Barnett A. Rattner, Roger L. Hothem, Thomas W. Custer, Mark J. Melancon, Kirke A. King, Leonard J. Lecaptain, James W. Spann, Bruce R. Woodin, John J. StegemanAbstract: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.
Barnett A. Rattner - One of the best experts on this subject based on the ideXlab platform.
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Absorption and biotransformation of polybrominated diphenyl ethers DE-71 and DE-79 in chicken (Gallus gallus), mallard (Anas platyrhynchos), American kestrel (Falco sparverius) and Black-Crowned Night-Heron (Nycticorax nycticorax) eggs.
Chemosphere, 2010Co-Authors: Moira Mckernan, Barnett A. Rattner, Jeff S. Hatfield, Robert C. Hale, Mary Ann OttingerAbstract:Abstract We recently reported that air cell administration of penta-brominated diphenyl ether (penta-BDE; DE-71) evokes biochemical and immunologic effects in chicken ( Gallus gallus ) embryos at very low doses, and impairs pipping (i.e., stage immediately prior to hatching) and hatching success at 1.8 μg g −1 egg (actual dose absorbed) in American kestrels ( Falco sparverius ). In the present study, absorption of polybrominated diphenyl ether (PBDE) congeners was measured following air cell administration of a penta-BDE mixture (11.1 μg DE-71 g −1 egg) or an octa-brominated diphenyl ether mixture (octa-BDE; DE-79; 15.4 μg DE-79 g −1 egg). Uptake of PBDE congeners was measured at 24 h post-injection, midway through incubation, and at pipping in chicken, mallard ( Anas platyrhynchos ), and American kestrel egg contents, and at the end of incubation in Black-Crowned Night-Heron ( Nycticorax nycticorax ) egg contents. Absorption of penta-BDE and octa-BDE from the air cell into egg contents occurred throughout incubation; at pipping, up to 29.6% of penta-BDE was absorbed, but only 1.40–6.48% of octa-BDE was absorbed. Higher brominated congeners appeared to be absorbed more slowly than lower brominated congeners, and uptake rate was inversely proportional to the log K ow of predominant BDE congeners. Six congeners or co-eluting pairs of congeners were detected in penta-BDE-treated eggs that were not found in the dosing solution suggesting debromination in the developing embryo, extraembryonic membranes, and possibly even in the air cell membrane. This study demonstrates the importance of determining the fraction of xenobiotic absorbed into the egg following air cell administration for estimation of the lowest-observed-effect level.
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Element Patterns in Feathers of Nestling Black-Crowned Night-Herons, Nycticorax nycticorax L., from Four Colonies in Delaware, Maryland, and Minnesota
Bulletin of Environmental Contamination and Toxicology, 2008Co-Authors: Thomas W. Custer, Nancy H. Golden, Barnett A. RattnerAbstract:The pattern of elements in nestling Black-Crowned Night-Heron feathers from a rural Minnesota colony differed from colonies in industrialized regions of Maryland and Delaware. Except for chromium, however, the differences did not reflect the elements associated with waters and sediments of the Maryland and Delaware colonies. Therefore, elements in water and sediment do not necessarily bioaccumulate in Night-Heron feathers in relation to potential exposure. Although trace element patterns in feathers indicated differences among geographical locations, they did not separate all locations well and their usefulness as an indicator of natal colony location may be limited.
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Organochlorine contaminant exposure and reproductive success of Black-Crowned Night Herons (Nycticorax nycticorax) nesting in Baltimore Harbor, Maryland
Archives of Environmental Contamination and Toxicology, 2001Co-Authors: Barnett A. Rattner, Peter C. Mcgowan, J. S. Hatfield, Chia-swee HongAbstract:The declining size of the Baltimore Harbor Black-Crowned Night-Heron (Nycticorax nycticorax) colony has been hypothesized to be linked to polychlorinated biphenyl (PCB) exposure. In 1998, a “sample egg” was collected from 65 Black-Crowned Night-Heron nests (each containing ≥ three eggs) for contaminant analysis, and the remaining eggs in these 65 nests, plus four two-egg nests, were monitored for hatching and fledging success. Eggs were also collected from 12 nests at Holland Island, a reference site in southern Chesapeake Bay. Samples were analyzed for 26 organochlorine pesticides and metabolities and 145 PCB congeners. Pesticide and metabolite concentrations, including p,p'-DDE, were well below thresholds associated with adverse reproductive effects at both sites. Average concentration of total PCBs, 12 Ah receptor–active PCB congeners, and toxic equivalents in eggs from Baltimore Harbor were greater (up to 35-fold) than that observed in Holland Island samples. Overall nest success at the Baltimore Harbor Heronry was estimated by the Mayfield method to be 0.74, and the mean number of young fledged/hen was 2.05, which is within published productivity estimates for maintaining a stable Black-Crowned Night-Heron population. Using logistic regression, no significant relationships were found between organochlorine contaminant concentrations in sample eggs and hatching, fledging, or overall reproductive success. Processes other than poor reproduction (e.g., low postfledging survival, emigration, habitat degradation) may be responsible for the declining size of the Baltimore Harbor colony.
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Cytochrome P450 and organochlorine contaminants in black‐crowned Night‐Herons from the Chesapeake Bay region, USA
Environmental Toxicology and Chemistry, 1997Co-Authors: Barnett A. Rattner, Mark J. Melancon, Clifford P. Rice, Walter Riley, John D. Eisemann, Randy K. HinesAbstract: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. Bio-monitoring 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.
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Relation among cytochrome p450, ah‐active pcb congeners and dioxin equivalents in pipping black‐crowned Night‐Heron embryos
Environmental Toxicology and Chemistry, 1994Co-Authors: Barnett A. Rattner, Thomas W. Custer, Mark J. Melancon, Jeff S. Hatfield, Donald E. TillittAbstract:Pipping Black-Crowned Night-Heron (Nycticorax nycticorax) embryos were collected from a relatively uncontaminated site (next to 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). Hepatic cytochrome P450-associated mono-oxygenates and cytochrome P450 proteins, induced up to 85-fold relative to the reference site, were associated with concentrations of total polychlorinated biphenyls (PCBs) and 11 PCB congeners that are presumed to express toxicity through the arylhydrocarbon (Ah) receptor. Multiple regression revealed that up to 86% of the variation of cytochrome P450 measurements was accounted for by variation in the concentration of these PCB congeners. Toxic equivalents (TEQs) of sample extracts, predicted mathematically (summed product of PCB congener concentrations and toxic equivalency factors), and dioxin equivalents (TCDD-EQs), derived by bioassay (ethoxyresorufin-O-dealkylase activity of treated H4IIE rat hepatoma cells), were greatest in Cat Island samples. Cytochrome P450-associated monooxygenases and cytochrome P450 proteins were related to TEQs and TCDD-EQs; adjusted r[sup 2] often exceeded 0.5 for the relation among mathematically predicted TEQs and cytochrome P450 measurements. These data extend previous observations in Heron embryos of an association between P450 and total PCB burdens to include Ah-activemore » PCB congeners, and presumably other compounds, which interact similarly with the AH receptor. Benzyloxyresorufin O-dealkylase, ethoxyresorufin O-dealkylase, and cytochrome P450 1A appear to be the most reliable measures of exposure to Ah-active PCB congeners in Black-Crowned Night-Heron embryos. These findings provide further evidence that cytochrome P450-associated parameters have considerable value as a biomarker for assessing environmental contamination of wetlands.« less
Thomas W. Custer - One of the best experts on this subject based on the ideXlab platform.
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Contaminant exposure and biomarker response in embryos of Black-Crowned Night-Herons (Nycticorax nycticorax) nesting near Lake Calumet, Illinois
Journal of Great Lakes Research, 2020Co-Authors: Jeffrey M. Levengood, Thomas W. Custer, Mark J. Melancon, David J. Hoffman, Luann Wiedenmann, David J. Schaeffer, Cole W. Matson, John W. Scott, Jonathan L. Talbott, Gary BordsonAbstract:ABSTRACT We examined a suite of environmental contaminants and exposure endpoints in Black-Crowned Night-Heron (Nycticorax nycticorax, BCNH) embryos collected in 2002 from colonies in Illinois, Minnesota, and Virginia. Embryos from the Lake Calumet, IL, colony had greater exposure to polychlorinated biphenyls (PCBs), 4,4′-dichlorodiphenyldichloroethylene (DDE), dieldrin, transnonachlor, oxy-chlordane, cobalt, copper, and selenium than did those from northwest MN and coastal VA. Embryos from IL and VA contained greater concentrations of mercury and zinc than those from MN, whereas the latter had greater accumulation of lead. Greater exposure of IL embryos to PCBs was reflected in greater ethoxyresorufin-O-deethylase and benzyloxyresorufin-O-dealkylase induction. However, measures of oxidative stress and genotoxicity were similar to those in embryos from the other colonies examined, and no overt toxic effects of contaminant exposure such as embryo mortality or malformations were observed. Although efforts t...
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Contaminant exposure of birds nesting in Green Bay, Wisconsin, USA.
Environmental Toxicology and Chemistry, 2014Co-Authors: Thomas W. Custer, Christine M. Custer, Paul Michael Howell Dummer, J. Christian Franson, Michael JonesAbstract:In earlier studies, elevated concentrations of polychlorinated biphenyl (PCB) and p,p'-dichlorodiphenyldichloroethylene (DDE) were reported in double-crested cormorant (Phalacrocorax auritus) eggs and tree swallow (Tachycineta bicolor) eggs and nestlings collected from lower Green Bay (WI, USA) in 1994 and 1995 and Black-Crowned Night-Heron (Nycticorax nycticorax) eggs collected in 1991. Comparable samples collected in 2010 and 2011 indicated that concentrations of PCBs were 35%, 62%, 70%, and 88% lower than in the early 1990s in tree swallow eggs, tree swallow nestlings, double-crested cormorant eggs, and Black-Crowned Night-Heron eggs, respectively; concentrations of DDE were 47%, 43%, 51%, and 80% lower, respectively. These declines are consistent with regional contaminant trends in other species. Concentrations of PCBs were higher in herring gull (Larus argentatus) than in Black-Crowned Night-Heron eggs collected from Green Bay in 2010; PCB concentrations in double-crested cormorant and tree swallow eggs were intermediate. The estimated toxicity of the PCB mixture in eggs of the insectivorous tree swallow was the equal to or greater than toxicity in the 3 piscivorous bird species. A multivariate analysis indicated that the composition percentage of lower-numbered PCB congeners was greater in eggs of the insectivorous tree swallow than in eggs of the 3 piscivorous species nesting in Green Bay. Dioxin and furan concentrations and the toxicity of these chemicals were also higher in tree swallows than these other waterbird species nesting in Green Bay. Environ Toxicol Chem 2014;33:1832–1839. Published 2014 Wiley Periodicals, Inc. Published 2014 Wiley Periodicals, Inc. This article is a US Government work and, as such, is in the public domain in the USA.
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Element Patterns in Feathers of Nestling Black-Crowned Night-Herons, Nycticorax nycticorax L., from Four Colonies in Delaware, Maryland, and Minnesota
Bulletin of Environmental Contamination and Toxicology, 2008Co-Authors: Thomas W. Custer, Nancy H. Golden, Barnett A. RattnerAbstract:The pattern of elements in nestling Black-Crowned Night-Heron feathers from a rural Minnesota colony differed from colonies in industrialized regions of Maryland and Delaware. Except for chromium, however, the differences did not reflect the elements associated with waters and sediments of the Maryland and Delaware colonies. Therefore, elements in water and sediment do not necessarily bioaccumulate in Night-Heron feathers in relation to potential exposure. Although trace element patterns in feathers indicated differences among geographical locations, they did not separate all locations well and their usefulness as an indicator of natal colony location may be limited.
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Selenium and Metal Concentrations in Waterbird Eggs and Chicks at Agassiz National Wildlife Refuge, Minnesota
Archives of Environmental Contamination and Toxicology, 2007Co-Authors: Thomas W. Custer, Christine M. Custer, Bruce A. Eichhorst, David WarburtonAbstract:Exceptionally high cadmium (Cd) and chromium (Cr) concentrations were reported in eggs, feathers, or livers of selected waterbird species nesting at Agassiz National Wildlife Refuge (Agassiz) in 1994. Ten- to 15-day-old Franklin’s gull (Larus pipixcan), Black-Crowned Night-Heron (Nycticorax nycticorax), and eared grebe (Podiceps nigricollis) chicks were collected in 1998, 1999, and 2001 at Agassiz and analyzed for selenium (Se) and metals including Cd and Cr. Freshly laid eggs were collected in 2001 from Franklin’s gull, Black-Crowned Night-Heron, eared grebe, and pied-billed grebe (Podilymbus podiceps) nests at Agassiz. Based on a multivariate analysis, the pattern of Se and metal concentrations differed among species for eggs, chick feathers, and chick livers. Low Cd and Cr concentrations were measured in eggs, chick livers, and chick feathers of all four species. Mercury concentrations in Black-Crowned Night-Heron and eared grebe eggs collected from Agassiz in 2001 were lower than concentrations reported in 1994. Se and metal concentrations, including Cd and Cr, in waterbird eggs and chicks collected at Agassiz in 1998, 1999, and 2001 were not at toxic levels.
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Transfer and accumulation of organochlorines from black‐crowned Night‐Heron eggs to chicks
Environmental Toxicology and Chemistry, 1995Co-Authors: Thomas W. Custer, Christine M. CusterAbstract:Eggs and sibling 1-, 3-, and 5-d-old chicks from seven Black-Crowned Night-Heron (Nycticorax nycticorax) broods were collected from Green Bay, Wisconsin, and analyzed for organochlorines. The concentration (μg/g) of nine organochlorines either decreased (n = 7) or remained the same (n = 2) as the chicks grew older. In contrast, the total mass (μg) of these nine organochlorines increased (n = 7) or remained the same (n = 2) as the chicks grew older. Accumulation rates of mass (μg/d) between egg and 5-d-old chicks for each of the nine organochlorines were positive and varied from 0.2 μg/d (p,p′-DDT) to 42 μg/d (PCBs). These results suggest that the loss of contaminant mass from eggs to chicks reported in some earlier studies was because the entire carcass was not analyzed (i.e., not including skin, gastrointestinal tract, etc.). These results also support the use of contaminant accumulation rates as an indicator of local contamination.
Robert A. Grove - One of the best experts on this subject based on the ideXlab platform.
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Mercury and drought along the lower Carson River, Nevada: II. Snowy egret and Black-Crowned Night-Heron reproduction on Lahontan Reservoir, 1997–2006
Ecotoxicology, 2008Co-Authors: Elwood F. Hill, Charles J. Henny, Robert A. GroveAbstract:Mercury concentrations in the floodplain of the Carson River Basin in northwestern Nevada are some of the highest ever reported in a natural system. Thus, a portion of the basin including Lahontan Reservoir was placed on the U.S. Environmental Protection Agency’s Natural Priorities List for research and cleanup. Preliminary studies indicated that reproduction in piscivorous birds may be at risk. Therefore, a 10-year study (1997–2006) was conducted to evaluate reproduction of snowy egrets ( Egretta thula ) and Black-Crowned Night-Herons ( Nycticorax nycticorax ) nesting on Gull Island in Lahontan Reservoir. Special attention was given to the annual flow of the Carson River, the resultant fluctuation of this irrigation reservoir, and the annual exposure of snowy egrets and Night-Herons to methylmercury (MeHg). The dynamic character of the river due to flooding and drought (drought effect) influenced snowy egret and Night-Heron reproduction more so than did MeHg contamination of eggs. During an extended drought (2000–2004) in the middle of the study, snowy egret nests containing eggs with concentrations of MeHg (measured as total mercury [THg] ∼ 100% MeHg) ≥0.80 μg THg/g, ww, all failed, but in 1997 and 2006 (wet years with general flooding), substantial numbers of young were produced (but fewer than at nests where eggs contained
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Mercury and Drought Along the Lower Carson River, Nevada: I. Snowy Egret and Black-Crowned Night-Heron Annual Exposure to Mercury, 1997–2006
Archives of Environmental Contamination and Toxicology, 2007Co-Authors: Charles J. Henny, Elwood F. Hill, Robert A. Grove, James L. KaiserAbstract:The dynamic nature of the annual volume of water discharged down the Carson River over a 10-year period, which included a century flood and drought, was examined in order to gain a better understanding of mercury movement, biological availability, and exposure to waterbirds nesting at Lahontan Reservoir. Total annual water discharge directly influenced total mercury (THg) in unfiltered water above the reservoir and downstream of a mining area, whereas methyl mercury (MeHg) at the same site was negatively related to annual discharge. Annual water storage at Lahontan Reservoir in the spring and early summer, as expected, was directly related to annual Carson River discharge. In contrast to the findings from above the reservoir, annual MeHg concentrations in water sampled below the reservoir were positively correlated with the total discharge and the amount of water stored in the reservoir on 1 July; that is, the reservoir is an important location for mercury methylation, which agrees with earlier findings. However, unfiltered water MeHg concentrations were about 10-fold higher above than below the reservoir, which indicated that much MeHg that entered as well as that produced in the reservoir settled out in the reservoir. Avian exposure to mercury at Lahontan Reservoir was evaluated in both eggs and blood of young snowy egrets (Egretta thula) and Black-Crowned Night-Herons (Nycticorax nycticorax). Annual MeHg concentrations in unfiltered water below the reservoir, during the time period (Julian Days 90–190) when birds were present, correlated significantly with mercury concentrations in Night-Heron blood (r2 = 0.461, p = 0.027), snowy egret blood (r2 = 0.474, p = 0.024), and Night-Heron eggs (r2 = 0.447, p = 0.029), but not snowy egret eggs. A possible reason for lack of an MeHg water correlation with snowy egret eggs is discussed and relates to potential exposure differences associated with the food habits of both species. THg concentrations in water collected below the reservoir were not related to egg or blood mercury concentrations for either species.
Joanna Burger - One of the best experts on this subject based on the ideXlab platform.
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Metals in feathers of Black-Crowned Night-Heron (Nycticorax nycticorax) chicks from the New York Harbor Estuary
Archives of Environmental Contamination and Toxicology, 2009Co-Authors: V. Padula, Joanna Burger, S. H. Newman, Susan Elbin, Christian JeitnerAbstract:In heavily urbanized landscapes such as the New York Harbor Estuary, the local environment is subject to a variety of contamination sources. Environmental contaminants such as heavy metals and metalloids pose a risk to wildlife inhabiting the harbor. Metal concentrations in feathers indicate exposure and provide insight into the potential adverse effects on birds. In 2004 and 2005 down feathers were collected from 147 Black-Crowned Night Heron (Nycticorax nycticorax) chicks living on four island colonies in the New York Harbor Estuary, USA: Goose Island, Hoffman Island, North Brother Island, and Canarsie Pol. We examined geographical and interannual differences in concentrations of the metalloid arsenic (As) and the heavy metals cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg). Significant differences in metal concentrations were a function of location, with North Brother Island having the highest As concentrations and Goose Island having the highest Cr and Pb concentrations in feathers collected in 2004. In 2005, feather samples indicated Hoffman Island had the highest Cr concentrations and North Brother Island had the highest Pb and Hg concentrations. Concentrations of As, Cd, and Hg decreased significantly from 2004 to 2005 on North Brother Island, Hg on Hoffman Island decreased from 2004 to 2005, while Cr on Hoffman Island increased from 2004 to 2005. Cd and Pb concentrations were higher and As and Cr concentrations were generally lower than concentrations reported in previous studies. Further investigation is necessary on the declining population of Herons in the New York Harbor Estuary to determine specifically if birds are experiencing adverse effects from metal contaminants, or if organic contaminants, such as organic Hg or polychlorinated biphenyls (PCBs), are playing a role in this population’s decline.
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Heavy metal and selenium levels in feathers of young egrets and Herons from Hong Kong and Szechuan, China
Archives of Environmental Contamination and Toxicology, 1993Co-Authors: Joanna Burger, Michael GochfeldAbstract:Several species of Herons and egrets frequently nest in colonies in areas where humans also concentrate. Since the birds feed on intermediate-sized fish that themselves concentrate pollutants, they can be used not only to assess the levels of contaminants in avian tissues but as indicators of contaminants in the environment. The concentration of heavy metals and selenium in the breast feathers of fledgling Black-Crowned Night Herons Nycticorax nycticorax and Chinese pond Herons Ardeola bacchus from the Tu Jing Yan Heronry outside Chengdu, Szechuan Province in China; and from fledgling Black-Crowned Night Heron, little egret Egretta garzetta , great egret Egretta alba and cattle egret Bubulcus ibis from the Mai Po Heronry in Hong Kong, were determined. Breast feathers were also collected from adult great egrets in Hong Kong. Adult great egrets had significantly higher levels of all heavy metals than did young great egrets. There were no significant interspecific differences in metal levels among the young at Szechuan China, except for chromium (pond Herons had higher levels). There were significant differences among the young nesting at Hong Kong for all metals examined. Great egrets had lower, and Night Herons had higher, levels of lead than the other young. Night Herons also had the highest levels of cadmium, manganese, and selenium compared to the other young. Great egret chicks had the lowest mercury levels, while little egret had the highest levels. Lead levels for all the birds in both Hong Kong and Szechuan were among the highest in the world, and this was attributed to the continued use of leaded gasoline.
