Circadian clocks exist in all types of organisms and coordinate key biological processes, e.g. photosynthesis in phytoplankton (microalgae) and land plants. We asked whether a circadian rhythm sustains in phytoplankton when living under constant illumination without environmental cues. Here, we report the first transcriptomic architecture of persistent oscillatory gene expression in the model marine diatom, Phaeodactylum tricornutum living under constant illumination and temperature without environmental cues. We show that cyclic expression of a considerable number of genes involved in light harvesting and carbon fixation sustained after 24 hours of constant illumination (free-running), which could pose additional constraints on cell growth under constant light conditions. Over long-term adaptation to constant illumination, the majority of the rhythmic genes identified under diel light conditions lose their oscillatory expression in the absence of external entrainers, and the genes potentially controlled by persistent circadian clocks are primarily involved in transcriptional regulation and cell division. We find constant illumination leads to an increased average expression of transcription factors and cell division genes, while genes involved in the Calvin-Benson cycle and pigment biosynthesis are kept at low expression levels, which plays a role in the down-regulation of photosynthetic efficiency. By manipulation of the dark rest period, we confirm a fine-tuned light/dark cycle could dramatically improve photosynthetic efficiency in microalgae. Our results unveil a novel persistent circadian rhythm on photosynthetic regulation in marine phytoplankton and provide critical insights into the interaction between environmental signals and inheritable internal circadian clocks in diatoms.

With the continuous development of industry, the massive emission of carbon dioxide (CO₂) has become a global challenge that cannot be ignored due to its nature as the primary driver of global climate change and environmental crisis. Carbon neutrality is proposed as a global initiative to mitigate climate change. As a developing industrial country, China provides about one-third of global carbon emissions and has set a carbon-neutral goal by 2060. To achieve this goal, continuous efforts across the country are required. In this review, Zhejiang Province, one of the most developed regions in China, is set as a model for analysis. We first summarize the current situation of carbon emission in Zhejiang Province. Then, corresponding sustainable approaches such as ecological and industrial solutions for the reduction of future carbon emissions are introduced for Zhejiang Province. We also provide a direction for the realization of carbon neutrality, focusing on the most promising solutions for Zhejiang Province.

Diatoms are vital primary producers in marine ecosystems and play a key role in blue carbon sequestration. Although their circadian rhythms have been studied in isolation, how these rhythms are modulated by co-occurring bacteria remains unknown. Using a defined co-culture of the diatom Phaeodactylum tricornutum with the marine bacterium Aliivibrio fischeri, we observed time-dependent physiological and transcriptomic changes in P. tricornutum, including a 16.3% reduction in rhythmic genes with prolonged culture time. Genome-scale metabolic modeling suggested a biphasic response, with predicted biomass flux increasing by 81% at the early co-culture stage but decreasing by 87% during prolonged co-culture. Deconvolution of the transcriptome via AI-driven independent component analysis identified gene modules associated with silica transport and senescence-related responses under co-culture conditions. Together, these findings establish a systems-level framework that links interspecies interactions between diatoms and bacteria, providing mechanistic insights into how microbial associations influence phytoplankton chronobiology and rhythmic regulation.