Global distribution of Synechococcus and its carbon fixation potential in the ocean under climate change

Synechococcus , a key genus of marine cyanobacteria, plays a crucial role in global carbon fixation; however, its potential for carbon fixation under future climate change remains underexplored. Here, we utilize machine learning to analyze 689 Synechococcus reference genomes and 953 marine metagenomic samples, uncovering the global distribution of Synechococcus species and their carbon fixation genes. The abundance and carbon fixation potential of Synechococcus in the ocean are primarily driven by carbonate and dissolved oxygen concentrations; however, the highest levels are predominantly found in mid‐latitude and low‐latitude regions, respectively. This contrasting pattern can be attributed to the heterogeneity in carbon fixation potential among different Synechococcus species and their environmental adaptations. Without policy interventions, climate change is projected to decrease Synechococcus abundance by approximately 20% across roughly 25 million km 2 of the surface ocean, primarily in low‐latitude regions. Conversely, the abundance of genes related to carbon fixation in Synechococcus is projected to increase in 50.6% of surface ocean areas. Mitigating greenhouse gas emissions could help preserve current distribution patterns. These findings provide important insights for predicting the carbon fixation capacity and species distribution of marine ecosystems under climate change, along with their potential impacts.