Development of a rapid Hormosira banksii bioassay using chlorophyll a fluorescence

Publication Type:
Thesis
Issue Date:
2006
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- A wealth of information exists for chlorophyll a fluorescence applications in ecophysiology. However, the use of chlorophyll a fluorescence in marine ecotoxicology has been limited and this is especially true of macroalgal ecotoxicology. The primary objective of this thesis was to develop and describe a bioassay protocol that uses improvements on past macroalgal assay techniques to allow the photosynthetic capacity of Hormosira banksii gametes to be assessed using chlorophyll a fluorescence measurements. Two protocols (using H. banksii eggs or sperm) have been developed that allow for rapid assessment of toxic impact (less than 8 h) on macroalgal gametes. This rapid time-to-result allows for timely management decisions to be made. This is significant since past macroalgal bioassays have necessitated up to a 48 h delay before results are available to decision makers. In addition to this much improved rapidity of result, comparison between a germination based endpoint and the fluorescence endpoint has shown the fluorescence measure to be more sensitive to some classes of toxicant, more precise (in terms of Coefficient of Variation), and can also offer information on mechanistic pathways of toxicants. In order to validate 'real-world' use of the new fluorescence protocol, the sperm fluorescence bioassay was effectively applied to the assessment of interactive effects displayed by mixtures of anti-foulant compounds. Furthermore, a level of eco-relevance was demonstrated for the chlorophyll a fluorescence endpoint %PSII Inhibition. This is significant in that eco-relevance has not previously been experimentally demonstrated for a chlorophyll a fluorescence endpoint in ecotoxicology and the demonstrated link to higher level effects may have favourable implications as to future acceptance of fluorescence data into water quality guidelines. Essentially, this work describes the development of, and also the successful application of, a novel, fluorescence macroalgae bioassay that not only has advantages over currently employed methods, but also offers a powerful tool in both the rapid assessment of toxic impact on near-shore macroalgal communities, and as an effective toxicity screening tool.
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