Question: Nitrogen, a nutrient found in fertilizer, helps plants increase in size. Rainwater runoff often carries fertilizer into ponds and lakes. What effect does excess nitrogen have on organisms in a pond or lake ecosystem?

  Options: 
 A. Algae grows rapidly.
 B. Mutations occur gradually in fish.
 C. Clam shells are slowly weakened.
 D. Frogs adapt quickly to new food sources.
Answer: A