ALGAL OFF‐FLAVOR COMPOUNDS IN DRINKING WATER: CHEMICAL COMMUNICATION OR CHEMICAL WASTE?

Watson, S. B. National Water Research Institute, CCIW, P.O. Box 5050, Burlington, ON L7R 4A6 Canada Algae produce a diversity of potent metabolites that can modify surface water chemistry, with major socio‐economic implications. Although non‐toxic to humans, many algal volatile organic compounds (VOCs) cause unpleasant taste and odour (T/O), which undermines consumer confidence and increases their use of alternative and often unregulated drinking water sources. Conventional treatment may fail to remove or even intensify odour, depending on the algal species, the VOCs, and the background levels of organic material present in the source water. Furthermore, some VOCs may signal the presence of potentially toxic algal taxa. On the other hand, many odour‐causing compounds signal changes in growth or metabolism, in community composition, or in ecosystem function and health. Furthermore there is growing evidence that some of these VOCs act as chemical messengers or deterrents (semiochemicals). While many odour compounds are produced by a diversity of algal (and non‐algal) species, there are some general patterns in VOC chemistry and production dynamics among major algal divisions related to cell composition and the metabolic pathways involved. Depending on the VOCs and taxa, production may be intra‐ and/or extracellular, and vary over population cycles with environmental conditions. T/O events therefore can provide opportunities to increase our understanding of chemical interactions among organisms, and how these may lead to, or reflect changes at the level of the individual, the population, and the community.