Studies of Mercury Dynamics in Birds

Lewis, Sharon Alison (1991) Studies of Mercury Dynamics in Birds. PhD thesis, University of Glasgow.

Abstract

1. A review is presented of the use of seabirds as biomonitors of heavy metals and factors influencing mercury dynamics in birds. 2. The effect of atmospheric deposition on mercury levels found in the plumage of seabirds was assessed and found to be negligible. No difference was found between feathers exposed for ten months to the atmosphere and feathers sealed over the same period. 3. Significant differences were found between the tip, middle and bottom portion of the feather but this was concluded to be due to natural depletion of the body pool of mercury as the feathers grew and not due to the effect of exogenous contamination. 4. The effect of age and sex upon mercury concentrations in feathers of red-billed gulls was investigated. Feather concentrations were not influenced by age nor sex in adults nor chicks. Dietary specialisation was assumed to be an important determinant of mercury levels in this species. 5. The effect of growth development on tissue distribution and excretion in kittiwake chicks was examined. No age-related changes in the retention of mercury by any of the tissues analysed were found nor were any differences in mercury excretion apparent. There was a positive correlation between the total amount of mercury going into the plumage and age which was suggested to reflect an increase in the amount of mercury circulating in the blood of older birds. 6. No difference in the mercury distribution between the liver, kidney and pectoral muscle was found which differed markedly from results of other studies. It was suggested that this may be an indication that the levels in chicks were approaching a toxic threshold. 7. Mercury accumulation and excretion were investigated in laboratory-reared black-headed gull chicks in relation to mercury intake. There was an increase in the proportion of mercury deposited in the kidney as the dose increased. The proportional accumulation of mercury in the carcass was also dose-dependent. The amount of mercury administered had no effect on the total excretion rate. 8. Mercury accumulated differentially in the internal tissues, concentrations in the kidney were greater than in the liver which in turn exceeded concentrations found in the pectoral muscle. All feather types contained much higher mercury concentrations than internal tissues and there was a consistent difference between different feather types in relation to mercury content. There was a pronounced reduction in the concentration of mercury in the primary feathers as the growth sequence progressed. 9. An average of 71% of the dose administered was excreted over the fledging period. Of this, 22% of the dose was excreted into the feathers. Sixty five percent of the total body burden of mercury was present in the plumage after the completed moult. Of administered mercury, 49% was contained in the plumage. 10. The retention and excretion of mercury after a single dose of methyl mercury was investigated in male and female quail. The role of eggs in mercury excretion was also assessed. The birds accumulated mercury rapidly in their internal tissues and lost it relatively slowly. Mercury accumulated differentially in the internal tissues. Kidney concentrations exceeded liver concentrations which exceeded pectoral muscle concentrations. 11. For up to eight weeks after mercury administration there was a difference between the mercury levels in the internal tissues of male and female birds, with less mercury in the female tissues. Twelve weeks after administration differences in the mercury levels of the kidney and pectoral muscle were still found. 12. There was no difference in mercury levels of the male and female plumage, although total mercury excretion did differ between the sexes with females losing up to 80% of their mercury intake in the first four weeks after mercury administration compared to 40% lost by male birds. Male birds lost over 80% of the mercury intake via the faeces compared to only 44% lost this way by the females. Initial mercury concentration in the eggs was over 3.5 pg/g. Over 40% of the females' intake was lost by this route supporting the use of bird eggs to sample for environmental contamination. 13. The effect of sex and species on mercury retention was examined in two species of seabird (shags and kittiwakes) after a single dose of methyl mercury. The excretion of mercury into the eggs and chicks was also assessed. Mercury accumulated differentially in the internal tissues. In both species there was no difference between the concentration of mercury found in the liver and kidney although levels in both these tissues were greater than levels found in the pectoral muscle. 14. Mercury concentrations in both species of seabird were similar. There were differences in the total amount of mercury in the tissues analysed, shag tissues having up to four times the amount of mercury in their tissues as those of the kittiwakes. (Abstract shortened by ProQuest.).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Ecology, Toxicology, Environmental health
• Date of Award: 1991
• Depositing User: Enlighten Team
• Unique ID: glathesis:1991-78308
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 28 Feb 2020 12:09
• Last Modified: 28 Feb 2020 12:09
• URI: https://theses.gla.ac.uk/id/eprint/78308