Lawn fertilizers often contain phosphorus. Sometimes these fertilizers runoff into lakes. Once in a lake, the excess phosphorus may affect algal growth and cause eutrophication in the lake. Which BEST describes how the phosphorus affects the algae?
A. It improves algae adaptability.

B. It increases the number of trophic levels algae occupy.

C. It reduces algae habitat size.

D. It increases the carrying capacity of lakes for algae.