No kidding. Every green plant uses carbon dioxide during photosynthesis, releasing oxygen as a byproduct. A surfeit of CO2 would produce more lush forests, greener grass, all from more oxygen being infused into our atmosphere. Atmospheric CO2 affects the environment differently from aqueous solutions of it in the water table or oceans... which is merely to say that it wouldn't affect oceanic algae production as much as it would land-based vegetation.
Nothing but plusses all around.
8^)