Photosynthesis and chemosynthesis -- what's the diff? Well, while both are processes by which organisms produce food, photosynthesis is powered by sunlight while chemosynthesis runs on chemical energy. Prior to 1977, we didn't even know chemosynthetic communities existed, but we've now found them in hot springs on land and on the seafloor around hydrothermal vents, cold seeps, whale carcasses, and sunken ships. No one had ever thought to look for them, but these communities were there all along.