Geranyl pyrophosphate in sediments: a potentially limiting precursor associated with 2-MIB production by benthic...

Odor and taste episodes in drinking water remain a persistent global concern. In the Xuhu water source area of Lake Taihu (China), abrupt increases of 2-methylisoborneol (2-MIB) have frequently occurred following sediment resuspension, despite low cyanobacterial densities in the overlying water. To elucidate the mechanism, we performed laboratory column incubations with Xuhu sediments and water, cross-region incubations using sediments from multiple lake regions of Lake Taihu, and light-incubator cultures with odor-producing filamentous cyanobacteria (Planktothricoides, Pseudanabaena, Dolichospermum). Sedimentary geranyl pyrophosphate (GPP) was quantified by UPLC-MS/MS, and 2-MIB cyclase activity was determined by ELISA. Sediments were identified as the source of 2-MIB, with sediment-attached filamentous cyanobacteria as the dominant producers, supported by cyclase activity, biosynthetic gene expression, and microbial community analyses. Among lake regions, the concentration of GPP in surface sediments was strongly associated with whether 2-MIB was synthesized and released: eastern-region sediments with higher GPP yielded ∼17 ng L⁻¹2-MIB in overlying water after 14 d, versus ∼2 ng L⁻¹ in low-GPP regions. Light-incubator cultures further showed that exogenous (sedimentary) GPP markedly promotes 2-MIB production, with the largest per-biomass enhancement (5-6 ×) in Dolichospermum, a weak odor producer under GPP-limited conditions. These findings indicate that, in low-algal shallow systems such as Xuhu, odor formation is closely linked to and likely limited by precursor availability (GPP) in sediments, which largely derives from the decomposition of submerged macrophytes. Practically, targeted management of sedimentary GPP-especially rapid removal of macrophyte detritus after strong winds and focused sediment interventions near intakes-offers a direct lever to reduce the frequency and severity of odor events.