Geology topics

Katherine R. Stebbins

Publications and source records attributed to Katherine R. Stebbins.

15 recordsLinked to original sources

USGS2011

A comparison of the teratogenicity of methylmercury and selenomethionine injected into bird eggs

Methylmercury chloride and seleno-L-methionine were injected separately or in combinations into the fertile eggs of mallards (Anas platyrhynchos), chickens (Gallus gallus), and double-crested cormorants (Phalacrocorax auritus), and the incidence and types of teratogenic effects were recorded. For all three species,selenomethionine alone caused more deformities than did methylmercury alone. When mallard eggs were injected with the lowest dose of selenium (Se) alone (0.1 μg/g), 28 of 44 embryos and hatchlings were deformed, whereas when eggs were injected with the lowest dose of mercury (Hg) alone (0.2 μg/g), only 1 of 56 embryos or hatchlings was deformed. Mallard embryos seemed to be more sensitive to the teratogenic effects of Se than chicken embryos:0 of 15 chicken embryos or hatchlings from eggs injected with 0.1 μg/g Se exhibited deformities. Sample sizes were small with double-crested cormorant eggs, but they also seemed to be less sensitive to the teratogenic effects of Se than mallard eggs. There were no obvious differences among species regarding Hg-induced deformities. Overall, few interactions were apparent between methylmercury and selenomethionine with respect to the types of deformities observed. However, the deformities spina bifida and craniorachischisis were observed only when Hg and Se were injected in combination. One paradoxical finding was that some doses of methylmercury seemed to counteract the negative effect selenomethionine had on hatching of eggs while at the same time enhancing the negative effect selenomethionine had on creating deformities. When either methylmercury or selenomethionine is injected into avian eggs, deformities start to occur at much lower concentrations than when the Hg or Se is deposited naturally in the egg by the mother.

Archives of Environmental Contamination and Toxico↗

USGS2011

Toxicity of methylmercury injected into eggs when dissolved in water versus corn oil

In a previous study, the embryotoxicity of methylmercury dissolved in corn oil was compared among 26 species of birds. Corn oil is not soluble in the water‐based matrix that constitutes the albumen of an egg. To determine whether the use of corn oil limited the usefulness of this earlier study, a comparison was made of the embryotoxicity of methylmercury dissolved in corn oil versus water. Mallard ( Anas platyrhynchos ) and chicken ( Gallus gallus ) eggs were injected with methylmercury chloride dissolved in corn oil or water to achieve concentrations of 0, 0.2, 0.4, 0.8, and 1.6 µg/g mercury in the egg on a wet weight basis. Hatching success at each dose of mercury was compared between the two solvents. For mallards, 16.4% of the eggs injected with 1.6 µg/g mercury dissolved in water hatched, which was statistically lower than the 37.6% hatch rate of eggs injected with 1.6 µg/g mercury dissolved in corn oil, but no differences in hatching success were observed between corn oil and water at any of the other doses. With chicken eggs, no significant differences occurred in percentage hatch of eggs between corn oil and water at any of the mercury doses. Methylmercury dissolved in corn oil seems to have a toxicity to avian embryos similar to that of does methylmercury dissolved in water. Consequently, the results from the earlier study that described the toxicity of methylmercury dissolved in corn oil to avian embryos were probably not compromised by the use of corn oil as a solvent.

Environmental Toxicology and Chemistry↗

USGS2011

Teratogenic efects of injected methylmercury on avian embryos

Controlled laboratory studies with game farm mallards ( Anas platyrhynchos ) and chickens ( Gallus gallus ) have demonstrated that methylmercury can cause teratogenic effects in birds, but studies with wild species of birds are lacking. To address this need, doses of methylmercury chloride were injected into the eggs of 25 species of birds, and the dead embryos and hatched chicks were examined for external deformities. When data for controls were summed across all 25 species tested and across all types of deformities, 24 individuals out of a total of 1,533 (a rate of 1.57%) exhibited at least one deformity. In contrast, when data for all of the mercury treatments and all 25 species were summed, 188 deformed individuals out of a total of 2,292 (8.20%) were found. Some deformities, such as lordosis and scoliosis (twisting of the spine), misshapen heads, shortening or twisting of the neck, and deformities of the wings, were seldom observed in controls but occurred in much greater frequency in Hg-treated individuals. Only 0.59% of individual control dead embryos and hatchlings exhibited multiple deformities versus 3.18% for Hg-dosed dead embryos and hatchlings. Methylmercury seems to have a widespread teratogenic potential across many species of birds.

Environmental Toxicology and Chemistry↗

USGS2011

Hormesis associated with a low dose of methylmercury injected into mallard eggs

We injected mallard ( Anas platyrhynchos ) eggs with methylmercury chloride at doses of 0, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4 μg mercury/g egg contents on a wet-weight basis. A case of hormesis seemed to occur because hatching success of eggs injected with 0.05 μg/g mercury (the lowest dose) was significantly greater (93.3%) than that of controls (72.6%), whereas hatching success decreased at progressively greater doses of mercury. Our finding of hormesis when a low dose of methylmercury was injected into eggs agrees with a similar observation in a study in which a group of female mallards was fed a low dietary concentration of methylmercury and hatching of their eggs was significantly better than that of controls. If methylmercury has a hormetic effect at low concentrations in avian eggs, these low concentrations may be important in a regulatory sense in that they may represent a no-observed adverse effect level (NOAEL).

Archives of Environmental Contamination and Toxico↗

USGS2011

Oxidative stress response of Forster's terns (Sterna forsteri) and Caspian terns (Hydroprogne caspia) to mercury and selenium bioaccumulation in liver, kidney, and brain

Bioindicators of oxidative stress were examined in prebreeding and breeding adult and chick Forster's terns ( Sterna forsteri ) and in prebreeding adult Caspian terns ( Hydroprogne caspia ) in San Francisco Bay, California. Highest total mercury (THg) concentrations (mean±standard error;μg/g dry wt) in liver (17.7±1.7), kidney (20.5±1.9), and brain (3.0±0.3) occurred in breeding adult Forster's terns. The THg concentrations in liver were significantly correlated with hepatic depletion of reduced glutathione (GSH), increased oxidized glutathione (GSSG):GSH ratio, and decreased hepatic gamma-glutamyl transferase (GGT) activity in adults of both tern species. Prefledging Forster's tern chicks with one-fourth the hepatic THg concentration of breeding adults exhibited effects similar to adults. Total mercury-related renal GSSG increased in adults and chicks. In brains of prebreeding adults, THg was correlated with a small increase in glucose-6-phosphate dehydrogenase (G-6-PDH) activity, suggestive of a compensatory response. Brain THg concentrations were highest in breeding adult Forster's terns and brain tissue exhibited increased lipid peroxidation as thiobarbituric acid-reactive substances, loss of protein bound thiols (PBSH), and decreased activity of antioxidant enzymes, GSSG reductase (GSSGrd), and G-6-PDH. In brains of Forster's tern chicks there was a decrease in total reduced thiols and PBSH. Multiple indicator responses also pointed to greater oxidative stress in breeding Forster's terns relative to prebreeding terns, attributable to the physiological stress of reproduction. Some biondicators also were related to age and species, including thiol concentrations. Enzymes GGT, G-6-PDH, and GSSGred activities were related to species. Our results indicate that THg concentrations induced oxidative stress in terns, and suggest that histopathological, immunological, and behavioral effects may occur in terns as reported in other species.

California↗

USGS2010

Reproduction in mallards exposed to dietary concentrations of methylmercury

The purpose of this experiment was to use mallards ( Anas platyrhynchos ) tested under controlled conditions to determine how much harm to reproduction resulted from various concentrations of mercury in eggs. Breeding pairs of mallards were fed a control diet or diets containing 1, 2, 4, or 8 μg/g mercury, as methylmercury chloride. Mean concentrations of mercury in eggs laid by parents fed 0, 1, 2, 4, or 8 μg/g mercury were 0.0, 1.6, 3.7, 5.9, and 14 μg/g mercury on a wet-weight basis. There were no signs of mercury poisoning in the adults, and fertility and hatching success of eggs were not affected by mercury. Survival of ducklings and the number of ducklings produced per female were reduced by the 4 and 8-μg/g dietary mercury treatments (that resulted in 5.9 and 14 μg/g mercury in their eggs, respectively). Ducklings from parents fed the various mercury diets were just as heavy as controls at hatching, but by 6 days of age ducklings whose parents had been fed 4 or 8 μg/g mercury weighed less than controls. Because we do not know if absorption of mercury from our diets would be the same as absorption from natural foods, the mercury concentrations we report in eggs may be more useful in extrapolating to possible harmful effects in nature than are the dietary levels we fed. We conclude that mallard reproduction does not appear to be particularly sensitive to methylmercury.

Ecotoxicology↗

USGS2010

Intraperitoneal injections as a possible means of generating varied levels of methylmercury in the eggs of birds in field studies

The ideal study of the effects of methylmercury on the reproductive success of a species of bird would be one in which eggs contained mercury concentrations ranging from controls to very heavily contaminated, all at the same site. Such a study cannot be realized at a mercury contaminated area or under laboratory conditions, but could be achieved by introducing methylmercury into breeding females and allowing them to deposit mercury in their eggs. Female mallards (Anas platyrhynchos) were intraperitoneally injected with solutions of methylmercury chloride dissolved in corn oil, propylene glycol, dimethyl sulfoxide, mineral oil, Olestra, Crisco, lard, hard paraffin, and a combination of hard and soft paraffin. In some cases, egg laying was delayed, either due to the solvent itself (in the case of Olestra, Crisco, and lard) or to the highest concentration of methylmercury chloride (500 μg/g) in some of the solvents. Mercury in eggs ranged from a control level (< 0.1 μg/g) to approximately 14 μg/g on a wet weight basis, which more than covers the range of concentrations reported in wild bird eggs. Mercury concentrations in a series of eggs from the same female declined mostly due to excretion of mercury in prior eggs and not because of the length of time since the injection. Intraperitoneal injections hold promise in field studies where one would like to study the reproductive effects of a wide range of methylmercury levels in the eggs of a wild bird and under the natural conditions that exist in the field.

Environmental Toxicology and Chemistry↗

USGS2010

Evidence of weak contaminant-related oxidative stress in glaucous gulls (Larus hyperboreus) from the Canadian arctic

Environmental contaminants are transported over great distances to Arctic ecosystems, where they can accumulate in wildlife. Whether contaminant concentrations in wildlife are sufficient to produce adverse effects remains poorly understood. Exposure to contaminants elevates oxidative stress with possible fitness consequences. The glaucous gull ( Larus hyperboreus ), an Arctic top predator, was used as a bioindicator for investigating relationships between contaminant levels (organochlorines and polychlorinated biphenyls [OC/PCB], mercury [Hg], and selenium [Se]) and measures of oxidative stress (glutathione [GSH] metabolism and lipid peroxidation) in Canadian Arctic ecosystems. Contaminant levels were low and associations between contaminant exposure and oxidative stress were weak. Nevertheless, glutathione peroxidase activity rose with increasing hepatic Se concentrations, levels of thiols declined as Hg and OC/PCB levels rose, and at one of the two study sites levels of lipid peroxidation were elevated with increasing levels of hepatic Hg. These results suggest the possibility of a deleterious effect of exposure to contaminants on gull physiology even at low contaminant exposures.

Arctic↗

USGS2009

Enhanced reproduction in mallards fed a low level of methylmercury: An apparent case of hormesis

Breeding pairs of mallards ( Anas platyrhynchos ) were fed a control diet or a diet containing 0.5 µg/g mercury (Hg) in the form of methylmercury chloride. There were no effects of Hg on adult weights and no overt signs of Hg poisoning in adults. The Hg‐containing diet had no effect on fertility of eggs, but hatching success of eggs was significantly higher for females fed 0.5 µg/g Hg (71.8%) than for controls (57.5%). Survival of ducklings through 6 d of age was the same (97.8%) for controls and mallards fed 0.5 µg/g mercury. However, the mean number of ducklings produced per female was significantly higher for the pairs fed 0.5 µg/g Hg (21.4) than for controls (16.8). Although mercury in the parents' diet had no effect on mean duckling weights at hatching, ducklings from parents fed 0.5 µg/g Hg weighed significantly more (mean = 87.2 g) at 6 d of age than did control ducklings (81.0 g). The mean concentration of Hg in eggs laid by parents fed 0.5 µg/g mercury was 0.81 µg/g on a wet‐weight basis. At this time, one cannot rule out the possibility that low concentrations of Hg in eggs may be beneficial, and this possibility should be considered when setting regulatory thresholds for methylmercury.

Environmental Toxicology and Chemistry↗

USGS2009

Predicting mercury concentrations in mallard eggs from mercury in the diet or blood of adult females and from duckling down feathers

Measurements of Hg concentrations in avian eggs can be used to predict possible harm to reproduction, but it is not always possible to sample eggs. When eggs cannot be sampled, some substitute tissue, such as female blood, the diet of the breeding female, or down feathers of hatchlings, must be used. When female mallards (Anas platyrhynchos) were fed diets containing methylmercury chloride, the concentration of Hg in a sample of their blood was closely correlated with the concentration of Hg in the egg they laid the day they were bled (r 2 =0.88; p<0.001). Even when the blood sample was taken more than two weeks after an egg was laid, there was a strong correlation between Hg concentrations in female blood and eggs (r 2 =0.67; p<0.0002). When we plotted the dietary concentrations of Hg we fed to the egg-laying females against the concentrations of Hg in their eggs, the r 2 value was 0.96 (p<0.0001). When the concentrations of Hg in the down feathers of newly hatched ducklings were plotted against Hg in the whole ducklings, the r 2 value was 0.99 ( p<0.0003). Although measuring Hg in eggs may be the most direct way of predicting possible embryotoxicity, our findings demonstrate that measuring Hg in the diet of breeding birds, in the blood of egg-laying females, or in down feathers of hatchlings all can be used to estimate what concentration of Hg may have been in the egg.

Environmental Toxicology and Chemistry↗

USGS2009

A simplified method for correcting contaminant concentrations in eggs for moisture loss.

We developed a simplified and highly accurate method for correcting contaminant concentrations in eggs for the moisture that is lost from an egg during incubation. To make the correction, one injects water into the air cell of the egg until overflowing. The amount of water injected corrects almost perfectly for the amount of water lost during incubation or when an egg is left in the nest and dehydrates and deteriorates over time. To validate the new method we weighed freshly laid chicken (Gallus gallus) eggs and then incubated sets of fertile and dead eggs for either 12 or 19 d. We then injected water into the air cells of these eggs and verified that the weights after water injection were almost identical to the weights of the eggs when they were fresh. The advantages of the new method are its speed, accuracy, and simplicity: It does not require the calculation of a correction factor that has to be applied to each contaminant residue.

Environmental Toxicology and Chemistry↗

USGS2009

A nonlethal microsampling technique to monitor the effects of mercury on wild bird eggs

Methylmercury is the predominant chemical form of mercury reported in the eggs of wild birds, and the embryo is the most sensitive life stage to methylmercury toxicity. Protective guidelines have been based mainly on captive-breeding studies with chickens (Gallus gallus), mallards (Anas platyrhynchos), and ring-necked pheasants (Phasianus colchicus) or on field studies where whole eggs were collected and analyzed and the effects of the mercury were measured based on the reproductive success of the remaining eggs. However, both of these methods have limitations. As an alternative, we developed a technique that involves extracting a small sample of albumen from a live egg, sealing the egg, returning the egg to its nest to be naturally incubated by the parents, and then relating the hatching success of this microsampled egg to its mercury concentration. After first developing this technique in the laboratory using chicken and mallard eggs, we selected the laughing gull (Larus atricilla) and black-necked stilt (Himantopus mexicanus) as test subjects in the field. We found that 92% of the microsampled laughing gull eggs met our reproductive endpoint of survival to the beginning of hatching compared to 100% for the paired control eggs within the same nests. Microsampled black-necked stilt eggs exhibited 100% hatching success compared to 93% for the paired control eggs. Our results indicate that microsampling is an effective tool for nonlethally sampling mercury concentrations in eggs and, as such, can be used for monitoring sensitive species, as well as for improving studies that examine the effects of mercury on avian reproduction.

Environmental Toxicology and Chemistry↗

USGS2009

Mercury and drought along the Lower Carson River, Nevada: III. effects on blood and organ biochemistry and histopathology of snowy egrets and black-crowned night-herons on Lahontan Reservoir, 2002-2006

A 10-year study (1997-2006) was conducted to evaluate reproduction and health of aquatic birds in the Carson River Basin of northwestern Nevada (on the U.S. Environmental Protection Agency Natural Priorities List) due to high mercury (Hg) concentrations from past mining activities. This part of the study evaluated physiological associations with blood Hg in young snowy egrets (Egretta thula) and black-crowned night-herons (Nycticorax nycticorax), and organ biochemistry and histopathological effects in snowy egrets on Lahontan Reservoir (LR) from the period 2002-2006. LR snowy egret geometric mean total Hg concentrations (μg/g ww) ranged from 1.5 to 4.8 for blood, 2.4 to 3.1 liver, 1.8 to 2.5 kidneys, 1.7 to 2.4 brain, and 20.5 to 36.4 feathers over these years. For night-herons, mean Hg for blood ranged from 1.6 to 7.4. Significant positive correlations were found between total Hg in blood and five plasma enzyme activities of snowy egrets suggesting hepatic stress. Histopathological findings revealed vacuolar changes in hepatocytes in LR snowy egrets as well as correlation of increased liver inflammation with increasing blood and tissue Hg. Hepatic oxidative effects were manifested by decreased hepatic total thiol concentration and glutathione reductase activity and elevated hepatic thiobarbituric acid-reactive substances (TBARS), a measure of lipid peroxidation. However, other hepatic changes indicated compensatory mechanisms in response to oxidative stress, including decreased oxidized glutathione (GSSG) concentration and decreased ratio of GSSG to reduced glutathione. In young black-crowned night-herons, fewer correlations were apparent. In both species, positive correlations between blood total Hg and plasma uric acid and inorganic phosphorus were suggestive of renal stress, which was supported by histopathological findings. Both oxidative effects and adaptive responses to oxidative stress were apparent in kidneys and brain. Vacuolar change and inflammation in peripheral nerves were found to correlate with blood and tissue Hg. Hg-associated effects related to the immune system included alterations in specific white blood cells and lymphoid depletion in the bursa that were correlated with blood and tissue Hg. When the number of plasma variables that differed between young snowy egrets from the LR site and the reference site were compared between wet and drought years, over twice as many variables were affected during drought years. This resulted in many more variables correlating with blood total Hg during dry than during wet years, suggesting the combination of drought and Hg was more stressful than Hg alone. Drought may have exacerbated Hg-related effects as reported previously for overall productivity. This relationship was not evident in black-crowned night-herons, although data were more limited.

Nevada↗

USGS2009

Rapid increases in mercury concentrations in the eggs of mallards fed methylmercury

To determine how quickly breeding birds would have to feed in a mercury-contaminated area before harmful concentrations of mercury, as methylmercury, built up in their eggs, we fed female mallards ( Anas platyrhynchos ) a control diet or diets containing 0.5, 1, 2, 4, or 8 μg/g mercury (on what was close to a dry weight basis) as methylmercury chloride for 23 d. After 18 d on their respective mercury diets, the eggs of mallards fed 0.5, 1, 2, 4, or 8 μg/g mercury contained 97.8, 86.0, 89.9, 88.9, and 85.9%, respectively, of the peak concentrations reached after 23 d. Depending on the dietary concentration of mercury, no more than approximately a week may be required for harmful concentrations (0.5–0.8 μg/g, wet weight) to be excreted into eggs.

Environmental Toxicology and Chemistry↗

USGS2009

Factors related to the artificial incubation of wild bird eggs

Attempts to artificially incubate the eggs of wild birds have failed in many respects in duplicating the success of natural incubation. As part of a larger study we had the opportunity to artificially incubate the eggs of 22 species of birds (three domestic and 19 wild species). We report the successes and failures associated with artificial incubation of these eggs. Moisture loss varied widely, not only for Orders of birds but for similar species within an Order. Overall hatching success and success through to 90% of incubation varied for different Orders and for similar species. Humidity and temperature are critical elements in the artificial incubation of wild bird eggs and must be closely monitored throughout incubation to ensure the best possible chance of hatching. Even when these elements are addressed, artificial incubation still can not duplicate the success of incubation by the parent.

Avian Biology Research↗