Temperature-Dependent Regulation of Co-Occurring Toxins, Odor Compounds, and Disinfection By-Product Precursors in Two Bloom-Forming Species

Cyanobacterial blooms pose significant threats to aquatic ecosystems and drinking water safety, primarily through the release of diverse secondary metabolites. This study systematically explored the dynamics of secondary metabolites in <i>Microcystis aeruginosa</i> and <i>Anabaena</i> sp. under controlled conditions, focusing on the effects of temperature (10 °C, 25 °C, 35 °C) and growth phases (exponential, stationary, decline). Key parameters measured included cell density, dissolved organic carbon (DOC), microcystins (MC-LR, MC-RR), taste and odor compounds (<i>β</i>-cyclocitral, <i>β</i>-ionone), and disinfection by-product formation potentials (trihalomethanes (THMs) and haloacetic acids (HAAs)). Results revealed striking interspecific differences: <i>M. aeruginosa</i> exhibited significantly higher metabolite production, with peak DOC, extracellular MC-LR, and particulate <i>β</i>-cyclocitral observed in the decline phase at 25-35 °C. In contrast, <i>Anabaena</i> sp. showed an "early accumulation advantage" for THM precursors and "residual release" in the decline phase. Temperature played a critical regulatory role, with 25 °C as the optimal for most metabolites, while 35 °C enhanced extracellular release of dissolved <i>β</i>-cyclocitral in <i>M. aeruginosa</i>. Growth phase dynamics were consistent across species, with stationary and decline phases marked by elevated metabolite concentrations due to intensified synthesis and cell lysis, particularly for HAAs. These findings highlight species-specific metabolic strategies and their environmental drivers, providing critical insights for assessing and managing cyanobacterial bloom risks in aquatic ecosystems.