Question

Eutrophication may be due to

• A. Runoff from agriculture
• B. Pollution from septic systems
• C. Sewage sludge spreading
• D. All of the above

Answer 1

Answer: (D)

All of the above

Eutrophication is the natural aging of a lake by nutrient enrichment of its water. With time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus, which encourage the growth of aquatic organisms.

As the lake's fertility increases, algal bloom occurs. Algal bloom causes the deterioration of water quality and fish mortality and dead remains begin to be deposited on the lake bottom. Over the year, lake finally gets converted into the land.

Human activities increase the rate of nutrient enrichment in lakes. Runoff from agriculture and development, pollution from septic systems and sewers, sewage sludge spreading, and other human-related activities increase the flow of both inorganic nutrients and organic substances into ecosystems. Thus, the correct answer is option D.