Monitoring and regulating cyanobacterial metabolites (microcystins and geosmin) in aquatic systems.
Pestana, Carlos Joao
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Cyanobacterial secondary metabolites can cause serious harm to animals and humans (cyanotoxins) and can have a major financial impact on the potable water and aquaculture industries (taste and odour compounds). Understanding the factors that affect cyanotoxin production can help in exploring means for the control of these secondary metabolites. One of the most prominent cyanotoxins are microcystins and their sister compound nodularin. The biological role of microcystins is poorly understood. A pheromonal effect was observed applying a novel stable isotope labelling (15N) method. Microcystin- LR has been shown to stimulate culture growth, limit microcystin synthesis, and affect the distribution of microcystin-LR between the intra- and extracellular matrices. Furthermore the control of microcystins in potable water has been explored applying photocatalysis over titanium dioxide. A novel product called Photospheres™ was assessed in its photocatalytic efficiency in the destruction of 12 microcystin analogues and nodularin. The photocatalytic efficiency of the Photospheres™ was further explored in the degradation of four common waste water pollutants (2-chlorophenol, p-cresol, Acid Orange 74, and trichloroethylene) and in a custom built reactor using light emitting diodes as source of irradiation. The monitoring and regulation of cyanobacterial taste and odour compounds, especially geosmin and 2- methylisoborneol is important in the potable water and aquaculture industries. A rapid, robust, sensitive, and cost-effective analysis method using SPE-GCMS has been developed and is capable of detecting both compounds to sub nano gram levels. The method was successfully applied on spiked laboratory and environmental samples (loch and fishfarm waters). The photocatalytic destruction of both 2-methylisoborneol and geosmin was explored with a custom built flow reactor that was able to degrade > 95 % of both compounds in spiked and environmental samples. Furthermore the application of silicone rubber membranes as passive samplers was explored in spiked and environmental samples, demonstrating that silicone rubber membranes can successfully be used in environmental applications to deliver rapid and accurate determinations of both 2-methylisoborneol and geosmin.