Samples for geosmin analyses were pre-concentrated using a solid phase microextraction syringe fibre (Supelco, Australia) and analysed on a 7890 Gas Chromatograph System with 5975C VL Series Mass Selective Detector (Agilent Technologies, Australia) against quantified labelled internal standards (Ultrafine Chemicals, UK). Full details of this method have been documented by Graham and Hayes (1998).