Heavy Metals and Metallothionein in Seabirds, With Reference to Their Use As Biomonitors

Stewart, Fiona M (1994) Heavy Metals and Metallothionein in Seabirds, With Reference to Their Use As Biomonitors. PhD thesis, University of Glasgow.

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Abstract

The use of seabirds as biomonitors is introduced and their applications to various aspects of monitoring discussed. A review of cadmium in birds is presented. The tissue distribution, uptake and storage of cadmium, the role of metallothionein, accumulation, excretion, toxicity and intra and inter-specific variation in heavy metal concentrations are discussed. Recent lies in monitoring are summarised. Biomonitoring of cadmium using feathers and eggs is assessed. It was concluded that feathers and eggs were of no value as monitors of cadmium in the marine environment. Cadmium concentrations in the internal tissues of adult lesser black-backed gulls are significantly higher than in immature gulls, but the accumulation patterns of cadmium into liver and kidney of the two age classes were the same. No increase in cadmium concentrations in internal tissues with age were detected in known age great skuas (aged 3-21 years), even when data were combined with a previous study (total n = 40). Dietary specialisation is probably important in determining the differences between individuals in cadmium concentrations and may mask the effects of age. To date, there are no studies demonstrating continuing cadmium accumulation with increasing age in fully grown seabirds. The relationships between cadmium, zinc, copper and metallothionein concentrations were investigated in adult lesser black-backed gulls. A metal-binding protein was investigated using gel filtration. The protein was bound to the metals cadmium, zinc, and copper, was a low molecular weight protein, and was heat resistant. This protein also and onto the Ag+ in the silver saturation assay and it was concluded that it was almost certainly a metallothionein. levels between April and June, and feathers were thought to be the main excretion route of mercury during moult, from June to November. 14. The fluctuations in cadmium were thought to be due to one of two hypotheses. 1. Physiological processes during breeding and moult created changes in the body burdens of metals. 2. Seasonal dietary changes were responsible for the changes. There were dietary switches during the sampling period which could create a change in cadmium concentrations in the prey items. 15. It was proposed that cadmium in seabirds could have a shorter biological half-life than previously thought, and they may have some kind of regulatory ability. 16. An experimental study of the uptake and assimilation of cadmium and its effects on other metals and metallothionein in great skua chicks was conducted. 17. The dose response of birds did not vary significantly over the range of doses administered. Mean uptake was 0.51% of the dose. Tissue distribution was dose-dependent, at low doses kidney was the preferential site of accumulation, and at higher doses the liver accumulated more than the kidney. 18. Experimentally increased cadmium concentrations in bird tissues affected the concentrations of metallothionein and the essential metals zinc and copper, all of which increased with increasing cadmium concentrations. 19. There were no consistent changes in the concentration of metallothionein in the experimental birds, when compared to the control birds. This was thought to be due to the excess metal being bound up by the metallothionein already present in the chicks' liver, kidney and duodenum. 20. Great skua chicks absorbed a low percentage of cadmium from a given dose in comparison to mammals and terrestrial birds, and this did not change with increasing dose. The possibility that seabirds are more resistant to the presence and effects of cadmium than other animals was discussed.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Bob Furness
Keywords: Ecology, Environmental health, Toxicology, Biogeochemistry
Date of Award: 1994
Depositing User: Enlighten Team
Unique ID: glathesis:1994-76388
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 14:46
Last Modified: 19 Nov 2019 14:46
URI: http://theses.gla.ac.uk/id/eprint/76388

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