Morphological and physiological adaptations of Dolichospermum flos-aquae to turbulence

Heterocystous cyanobacteria are increasingly forming surface blooms in freshwater ecosystems, with massive proliferation events influenced by multiple environmental factors-among which turbulence has emerged as a pivotal driver. This study investigated the effects of different turbulence intensities (ranging from 10^-5 to 10^-2 m² s^-3, within the natural environmental range) on the morphology and physiology of the bloom-forming diazotroph Dolichospermum flos-aquae. Results showed that high-intensity turbulence promoted population growth, dissolved nitrogen uptake, and photosynthetic performance of D. flos-aquae. Under high turbulence conditions, filament length exhibited greater uniformity alongside an increase in average length. Furthermore, heterocyst production was markedly enhanced, with no alteration in the spatial localization of heterocysts along filaments. These phenotypic responses were associated with upregulated carbon and nitrogen metabolisms-particularly nitrogen assimilation and carbon fixation-supported by the increased expression of key functional genes. Collectively, these findings reveal the morphological and physiological adaptive strategies of heterocystous cyanobacteria to turbulent environments, thereby advancing our understanding of diazotrophic cyanobacterial bloom dynamics in hydrologically dynamic freshwater ecosystems.