Which water condition is listed as contributing to HAB development because it reduces mixing and promotes algal blooms?

• A. Turbulent water
• B. Calm water
• C. High-flow rivers
• D. Crystalline water

Answer: (B)

Calm water reduces vertical mixing, allowing a stable surface layer to form where the water gets warmer and nutrients from runoff can concentrate near the surface. With light abundance and these nutrients, algae can grow rapidly, creating blooms that may become harmful. Turbulent water, by contrast, mixes the water more, spreading nutrients and preventing the long-lived surface layer that blooms need. High-flow rivers flush nutrients through the system, shortening the residence time needed for blooms to develop. Crystalline water describes clarity but doesn’t by itself drive the conditions that promote blooms. So, the lack of mixing in calm water best explains why algal blooms can develop into HABs when nutrients are available.