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The potential use of metal ratios in the gills of rainbow trout as biomarkers for acute waterborne copper exposure

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Daglish, Ross William (2004) The potential use of metal ratios in the gills of rainbow trout as biomarkers for acute waterborne copper exposure. PhD thesis, University of Tasmania.

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Abstract

This thesis examined the effects of short-term, acute copper poisoning on the metal
concentrations in the gills of rainbow trout (Oncorhynchus mykiss) with the aim of
developing possible biomarkers under such exposure regimes. The experiments were
designed principally to mimic the spillage of high copper contaminants such as
industrial or mining wastes into an environment which would flush the contaminant
quickly through the water system, resulting in a brief, but acute exposure to copper for
the inhabitants of the environment. A variety of water quality conditions were
investigated including in fresh and brackish waters, in conjunction with elevated zinc
levels in fresh waters and in brackish waters high in dissolved organic carbons.
The use of the gill copper concentrations in a ratio to other metals in the gills was
investigated for their potential role as biomarkers for acute copper exposure and in
fish kills. The depuration rates of metals from the gills were also examined in the
carcasses of animals killed through exposure to elevated levels of dissolved copper in
fresh and brackish waters. Data from fish kills in Macquarie Harbour, a large,
brackish inlet on the western coast of Tasmania, Australia, historically known for its
copper contamination, were included in the thesis.
It was demonstrated that in short-term, acute exposure to copper, hepatic copper
levels will not reflect the exposure whereas copper/metal ratios in the gills of rainbow
trout may do so. Circulating copper levels in the animal's blood plasma were
unaffected. When exposed to mixtures of copper and zinc, the ratios may still be
effective indicators, particularly the copper/sodium ratio. Copper residues in the gills were elevated while sodium levels in the gills and calcium levels in the plasma also
decreased significantly indicating an interruption to the animal's ability to iono-regulate.

However in brackish waters copper ratios appear less viable as biomarkers. Altered
physiological requirements between the animals in a hypotonic, isotonic and
hypertonic ionic environment affected copper accumulation at the gills and the
concentrations of other metal in the gills. Metal concentrations in the gills equilibrated
to environmental levels in 6 to 45 hours post-mortem. It was observed the postmortem
depuration of sodium from gill tissue in both fresh and brackish water may
provide a means of quantifying the time since death of animals in fish kills. Copper
loads in the gills of animals from fish kills in Macquarie Harbour were as high as
those of animals killed by copper exposure in laboratory trials in waters of the same
salinity, yet the copper/zinc ratios did not indicate that copper exposure was the cause
of mortality.
Data was also presented indicating high levels of naturally occurring dissolved
organic carbon in brackish waters can have an ameliorative effect on the toxicity of
copper to rainbow trout. The concentrations of copper that accumulated in the gills of
the exposed rainbow trout decreased as the levels of dissolved organic carbons
increased. The concentrations of copper correlated better with the total measured
copper in the water column than with the ASV-labile measurements of copper. This
indicated ASV-labile copper does not provide a good indicator of the bioavailable
fraction of the total measured copper.

Item Type: Thesis (PhD)
Keywords: Rainbow trout, Indicators (Biology), Copper
Copyright Holders: The Author
Copyright Information:

Copyright 2004 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D)--University of Tasmania, 2004. Includes bibliographical references

Date Deposited: 09 Dec 2014 00:09
Last Modified: 19 Jul 2016 02:49
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