Encouraging the Growth (Via Nutrient Fertilization)of Photosynthetic Protists in Marine

Encouraging the growth (via nutrient fertilization) of photosynthetic protists in marine environments may help reduce global warming.Why?

A) Photosynthetic protists give off a lot of carbon dioxide,and fertilizing them would increase carbon dioxide levels in the atmosphere.
B) Photosynthetic protists fix atmospheric carbon dioxide,decreasing carbon dioxide levels in the atmosphere.
C) Photosynthetic protists use a lot of oxygen,and fertilizing them would decrease oxygen levels in the environment.
D) Photosynthetic protists would release a lot of oxygen,and fertilizing them would increase levels of oxygen in the atmosphere.