In this CASE Studentship PhD project we aim to understand the drivers of elevated VOC production (Geosmin and 2-MIB) in drinking water reservoirs within the Wessex Water catchment. Episodic outbreaks of Geosmin and 2-MIB have occasionally, though not always, been associated with planktonic cyanobacterial blooms in Wessex reservoirs, but more recently, benthic communities have been identified as potential and significant sources of the VOCs, (Wessex Water, unpublished data). Focussing on three reservoirs and their associated catchments, we will analyse the distribution, transport and fate of these VOCs and their response to water treatment processes. The specific aims are: i) to isolate potential VOC producing microorganisms from the benthic and pelagic regions of the three reservoirs (and from the immediate catchment); ii) to examine intra-and interspecific variability in Geosmin and 2-MIB production under a range of experimental regimes; iii) to determine the degree of compartmentalisation between dissolved and particulate fractions of VOCs; iv) identify conditions that lead to the exudation of VOCs with a specific focus on the role(s) of viral lysis, protozoan and crustacean grazers, using isolated benthic and pelagic VOC-producing microorganisms.