Yunfei Sun

Diel cycles drive cyanobacterial physiology, yet the transcriptional and metabolic networks underlying diel adaptation in bloom‐forming Microcystis remain poorly understood. We integrated physiological measurements, transcriptomics and metabolomics to investigate diel dynamics of Microcystis aeruginosa under a 14‐h:10‐h light–dark cycle. M. aeruginosa exhibited clear diel rhythms in photosynthesis, cell division, and cell volume, with daytime as the active growth phase. Transcriptomically, daytime‐upregulated genes were enriched in anabolic pathways (e.g., photosynthesis, fatty acid, chlorophyll and arginine biosynthesis), whereas nighttime‐upregulated genes were associated with catabolic pathways (e.g., TCA cycle and purine/pyrimidine metabolism). Transporter genes remained active throughout the cycle. Metabolically, daytime featured higher levels of carbon fixation intermediates, nitrogen‐rich peptides and purine nucleosides, while nighttime showed enrichment of α‐linolenic acid and caffeoyl tyrosine. The metabolic network was organized into two opposing but internally correlated modules: a day‐enriched anabolic module and a night‐enriched catabolic module. Collectively, M. aeruginosa orchestrates a tightly coordinated diel trade‐off between daytime anabolism and nighttime catabolism to optimize light energy utilization and metabolic efficiency. These findings provide a multi‐omics mechanistic basis for understanding how M. aeruginosa exploits diel cycles for competitive success and offer time‐sensitive insights for monitoring and managing cyanobacterial blooms.

Artificial light at night (ALAN), intensified by coastal urbanization, is an emerging threat to coastal ecosystems. We used the rotifer Brachionus plicatilis and its prey Phaeocystis globosa as a model predator–prey system to examine rotifer life-history traits, predator–prey dynamics, and transcriptomic responses under varying ALAN intensities. ALAN altered maturation timing without affecting lifespan, and it reduced fecundity, population growth, and clearance rate, thereby delaying the depletion of P. globosa. Transcriptomic and network analyses showed that rotifers exposed to ALAN exhibited altered expression of candidate regulatory genes, including cytoskeleton-associated protein 5 (ckap5) and Raf proto-oncogene, serine/threonine kinase (raf) family members. These changes were associated with a CKAP5-associated microtubule module, RAF/PKA-related signaling, reproductive and cell-cycle-related pathways, and FoxO/autophagy-associated cellular-maintenance processes. These molecular responses provide potential regulatory clues for interpreting the phenotypic changes observed under ALAN exposure. Our findings help evaluate the potential effects of ALAN on zooplankton performance, and provide a scientific basis for assessing the environmental risks of coastal light pollution.

Nitrite and ammonia are two of the most common toxic nitrogenous pollutants in aquatic ecosystem, which can pose a serious threat to the health of aquatic organisms. Cladocerans, as an important part of freshwater ecosystem, will inevitably be harmed by these pollutants. To evaluate the combined toxic effects of these nitrogenous pollutants on cladocerans, we simulated 15 combinations of five nitrite concentrations (0, 0.5, 2, 4, 8 mg L⁻¹) and three ammonia concentrations (0, 0.1, 1 mg L⁻¹) to study the changes of life history traits of Daphnia pulex exposed to these combinations for 21 days. Results showed that under the combined stress of nitrite and ammonia, the survival time of D. pulex was shortened, the time to first batch of eggs and time to first brood were delayed, the body size and tail spine length at maturation were reduced, and the total offspring and the number of broods were decreased. There were some synergistically negative effects between the two nitrogenous pollutants. The presence of ammonia reduced the tolerance of D. pulex to nitrite, and vice versa. These findings provided new insights into the combined toxic effects of nitrite and ammonia on the life history traits of cladocerans, and were of great significance for understanding the population dynamics of specific species in cladocerans community under the condition of compound nitrogenous pollutants.

Inducible defenses occur in various taxa of prey organisms. Many phytoplankton species, including the freshwater Chlorophyta Tetradesmus spp., can form defensive morphs under the zooplankton‐released grazing cues. However, definite statements on the actual mechanisms of inducible defense in phytoplankton are quite deficient. In the present study, the defensive mechanism of Tetradesmus obliquus (formerly known as Scenedesmus obliquus) induced by Daphnia infochemicals was analyzed through multifaceted analyses integrating physiological and biochemical monitoring, transcriptomics, and metabolomics. Results showed that the upregulated genes encoding G protein‐coupled receptor and phospholipase C were involved in the perception and transduction of grazing cues, and the transcripts related to extracellular polysaccharides formation and transductions were upregulated. The results provided molecular evidence for the role of extracellular polysaccharides in colony formation. Increased lipid content revealed through metabolomics suggested higher investment in lipid biosynthesis within colonial cells, whereas the downregulation of ribosome‐related pathways indicated less allocation of energy and resources to protein biosynthesis. The significant increase in indole‐3‐acetic acid content indicated that growth was activated under grazing cues. This study provided essential information on the inducible defensive mechanism of Tetradesmus and direct evidence for the intracellular reallocation of resources and energy owing to the defensive colony formation, which had considerable implications for enriching the theory of inducible defenses at the molecular level.