6co2 + 6h2o + light → ch12o6 + 602
cah12o6 + 602 → 6co2 + 6h2o + energy
how do these equations explain why the total amount of o2 and co2 remains the same?

the species living around the vents are especially good at dispersal.  

deep-sea vent originates on the floor of the ocean when seawater circulates through hot volcanic rocks, usually situated where the new oceanic crust is being produced.  

biological dispersal refers to the movement of species from their location of birth to their site of breeding, or from breeding site to another. similarly, the oceanic dispersal refers to the movement of the species from one land mass to another by sea crossing.