What evidence is there that oxygen levels in the sea increased due to photosynthetic bacteria?

a. global cooling

b. rust deposits in today’s ocean

c. rust deposits in the ancient ocean

d. decreases in anaerobic organisms

Explanation:

Sedimentary layers of iron oxides is one of the main evidence certifying that oxygen levels in the sea increased due to photosynthetic bacteria. Burial of organic matter was formed mostly 2,400 million years ago.

The iron layers in seawater were formed with in-depth production of oxygen by photosynthetic bacteria. When these microbes die, their remains become buried in seafloor. Their decomposition removes oxygen from seawater and the released oxygen combines with dissolved iron and forms insoluble iron oxides.

Hence, rust formations reflect the rapid increase in oxygen concentration in seawater, which was related with the active photosynthetic processes.