Underlying mechanisms of spatial distribution of prokaryotic community in surface seawater from Arctic Ocean to the Sea of Japan.

Microorganisms play critical roles in marine ecosystems, so understanding the factors shaping microbial communities across various oceanic regions is essential for predicting ecosystem resilience and biogeochemical cycles. This study investigated the marine prokaryotic communities across 22 stations spanning the Arctic Ocean, the Chukchi Sea, the Bering Sea, and the Sea of Japan, with an emphasis on how environmental factors shape these communities. Results showed that the microbial alpha diversity generally declines with increasing latitude, though Arctic Ocean stations exhibited higher Chao 1 indices compared to the Bering Sea. Beta diversity analyses revealed that temperature and salinity were key factors associated with community composition variation across latitudes. Proteobacteria and Cyanobacteria were the dominant phyla showing opposite distribution trends across sampling stations. Cold-adapted oligotrophs such as and the SAR11 clade thrived in Arctic waters, while known for pollutant degradation, was more abundant in the Sea of Japan. Temperature was positively correlated to the relative abundance of . At broad spatial scales, stochastic processes dominated community assembly of microbial phylogenetic diversity, while in specific regions like the Arctic Ocean, deterministic homogeneous selection appeared to shape microbial communities; and temperature showed a pronounced influence on phylogenetic turnover across all samples. Co-occurrence networks identified several key taxa, such as , , and . Overall, the study underscores temperature's role in shaping microbial community diversity, composition, and assembly processes across latitudinal gradients, highlighting unique community adaptations to extreme environments.IMPORTANCEMicrobes are the invisible engines of ocean health, recycling nutrients and sustaining marine life. This research helps us understand how climate factors like temperature shape these microscopic communities, which differ starkly between icy Arctic waters and warmer seas. As oceans warm due to climate change, microbial populations and their critical roles in cleaning pollutants or supporting food webs could shift dramatically. The study suggests Arctic microbes are uniquely adapted to cold, low-nutrient conditions, making them vulnerable to warming. By linking temperature to microbial diversity, this work provides clues to predict how marine ecosystems might respond to climate shifts, informing efforts to protect ocean biodiversity and processes vital to Earth's carbon and nutrient cycles.