Grant: Discovery Grants Program - Individual

Drinking water Taste and odour (T&O) is a serious problem in Canada, costing the water, food & beverage, tourist and aquaculture industries millions annually. Most T&O is caused by the earthy-muddy compounds geosmin (GSM) and 2-methylisoborneol (MIB), produced by photosynthetic and non-photosynthetic (heterotrophic) microorganisms. Yet despite significant advances, we still cannot predict and manage most GSM and MIB events, because we cannot trace the source organisms, and do not understand why these compounds are produced. Two key questions will be addressed. First, 'WHICH ORGANISMS ARE KEY GSM AND MIB PRODUCERS IN DIFFERENT SOURCE-WATERS? We will use stable isotopes (13C/12C ratios) to trace heterotrophic and photoautotrophic producers and the factors fuelling their production. We propose to measure the 13C/12C ratios for GSM and MIB in field samples and cultures fed with: i) natural organic C- sources from terrestrial and aquatic environs; ii) 13C-labelled inorganic and organic compounds (using light and dark treatments to control photosynthesis). Second, 'WHY ARE THESE COMPOUNDS PRODUCED?' I propose that GSM and MIB are not 'waste products', but instead, are produced as chemical 'signals'. Previous studies indicate very low activity. But GSM and MIB exist in 2 molecular forms, and the synthetic (+) forms applied in these experiments are far less odorous than the natural (-) molecules. This is likely true for any other biological activity they have. We will test the hypotheses that: i) most biota produce the (-) enantiomers, which will be verified from culture material and field samples from a diversity of aquatic and terrestrial environments; ii) there are major differences in the biological activity of these enantiomers as toxins, inhibitors, attractants or repellents, as assessed using grazers and cultures of algae and bacteria. This work will make a significant contribution towards more proactive water treatment and management by testing potentially valuable indicators of source-water odour.