Need help in science plz

There are specialized producers that live in warm water vents deep in the ocean. these producers do not per-form from photosynthesis, but instead perform a similar process with iron and other chemicals. why do you think these producers use this process instead of photosynthesis?

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?

This is the interaction of two organisms where one is and the other is neither nor harmed.