Four algal species commonly found in the River Seine were cultured for a comprehensive investigation of their odorous metabolites. Closed loop stripping analysis (CLSA), open stripping analysis (OSA) and steam distillation extraction (SDE) were used to extract and concentrate a wide range of metabolites. The odour causing compounds were identified by a combination of chemical (gas chromatography-mass spectrometry (GC-MS)) and sensory (sensory-gas chromatography (sensory-GC), flavour profile analysis (FPA)) analyses. The compounds found responsible for unpleasant odours were alkenes, saturated and unsaturated aliphatic alcohols, aldehydes, ketones, sulphides and pyrazines. Some of the odorous compounds responsible for septic and muddy/musty odours may have been of bacterial or fungal origin as the cultures were non-axenic. Sensory-GC was found to be a valuable tool in identifying compounds of very low odour thresholds, which were present at or below the detection limits of the GC-MS.