Stream pollution with nitrogen effects what downstream?

• A. Fish and ecosystems
• B. Water temperature changes
• C. Algae blooms exclusively
• D. Sediment accumulation

Answer: (A)

Nitrogen pollution in streams acts as a nutrient that fuels excessive growth of algae and aquatic plants. This rapid growth, especially downstream, drives eutrophication. As blooms develop and subsequently die, microbes break down the organic matter and consume large amounts of dissolved oxygen. The resulting low-oxygen conditions stress or kill fish and other aquatic organisms, and it also reshapes food webs and overall ecosystem health downstream. So the impact isn’t limited to algae alone; it affects the fish and the entire ecosystem that relies on the stream. The other options miss the broader ecological consequences or point to secondary effects not primarily caused by nitrogen in streams.