Which combination most strongly contributes to excessive aquatic plant mats?

• A. Warmer water alone.
• B. Nutrient enrichment alone.
• C. Warmer water temperatures with nutrient enrichment.
• D. Cooler water with nutrient depletion.

Answer: (C)

The main concept being tested is how temperature and nutrient availability interact to drive excessive aquatic plant growth. Warmer water speeds up plant metabolism and extends the growing season, so plants can grow faster. Nutrient enrichment provides more of the essential building blocks—like nitrogen and phosphorus—that plants and algae need to proliferate. When both conditions are present, growth is strongly amplified, leading to dense plant mats that can crowd out other life and reduce water quality.

If the water is warm but nutrients are scarce, growth is limited by the lack of food, so mats don’t develop as vigorously. If nutrients are plentiful but the water is cool, growth can still occur but at a slower pace. Cooler water with nutrient depletion further limits growth. The combination of warm temperatures with nutrient enrichment creates the most favorable environment for excessive aquatic plant mats.