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Title: Evaluating the potential of metallothionein as a reliable biomarker for metal pollution in selected marine organisms
Author: Oaten, James Francis Price
ISNI:       0000 0004 6422 6295
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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Metal pollution within coastal and estuarine environments is of concern due to its potential to decrease economic value to society, impact marine ecology, and reduce recreational use. Biomonitoring provides a valuable tool to monitor metal pollution as it allows the measurement of bioavailable metals, which have the highest potential to impact ecology and human health. Metallothionein (MT) is a biomarker of metal contamination; it is induced by metal exposure, binding and detoxifying metals within cells. MT has been included in numerous studies monitoring metal contamination using marine invertebrates. Causes of natural variation on MT concentrations such as reproduction, tissue mass, salinity, and temperature, are known issues in common bioindicator groups such as mussels and oysters. This can disrupt the relationship between MT and metal concentrations within marine invertebrates and cause MT to be a less reliable biomarker. Seasonal effects to MT concentrations are not definite in the Manila clam (Ruditapes philippinarum), an invasive clam species within the UK, which could be a promising bioindicator due to its increasingly global extent. Bioindicator species such as brown seaweeds (e.g. Fucus spiralis) have not been studied as a MT biomarker species despite their extensive use as a general metal bioindicator. Furthermore, standard protocols for the treatment of organisms before MT analysis have not been defined and studies are inconsistent. This may be causing further discrepancies between MT and metal concentrations due to changes in concentrations that may occur between sampling and MT analysis, perhaps due to stress endured during transportation or protein degradation during storage. Therefore, an aim of this PhD was to evaluate the potential of, and limits to, the use of MT in selected marine organisms. A further aim was to the refine the use of MT, in terms of both methodological protocols and seasonal sampling strategies, to increase its reliability as a biomarker. It was found that the most appropriate treatment of organisms before MT analysis is to transport samples on ice from the field to the laboratory, and dissect as soon as possible thereafter. Depuration of organisms is not recommended before MT analysis, and storage at -20°C is acceptable for up to 10 weeks rather than the much lower temperatures used in some studies. It was found that gametogenesis in clam species in Poole Harbour during spring causes MT to be induced independently of metal exposure, compromising the reliability of MT. This suggests that the sampling of organisms should be restricted to a period of resting reproductive status. The potential of spiral wrack (Fucus spiralis) as a sensitive MT biomarker species was found to be limited, but may show promise in heavily contaminated environments, and warrants further research. Each of these findings can be implemented into international monitoring programmes as protocol in order to refine the use of MT. This thesis recommends that the shortcomings of current monitoring programmes are amended to include: evidence-based standard protocols for the pre-treatment of organisms; advisory restriction of sampling during gameteogenic periods; and the use of a range species as MT biomarker species.
Supervisor: Williams, Ian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available