Extended Data Fig. 4: Formation of iron mineral on the surface of cyanobacterial mats.

SEM-EDS analysis of cyanobacterial mats collected from the photobioreactor on day 450. The SEM image shows cyanobacterial filaments partially covered by granular deposits identified as iron oxides. Elemental mapping of Fe, O, and C reveals strong co-localization of Fe and O, with negligible carbon signal, indicating the formation of iron mineral coatings on the cyanobacterial surface. Micrographs are representative results from 10 independent images.