High plant and animal density in water can cause brown water. What is this phenomenon called?

• A. Heavy Populations Effect
• B. Algal Bloom
• C. Sedimentation
• D. Turbidity Increase

Answer: (A)

When water becomes brown due to a lot of life in it, the best way to describe it is an algal bloom. This is when algae and other phytoplankton multiply rapidly, usually fueled by plenty of nutrients. The rapid growth colorfully tints the water and can make it appear brown because of the dense cells and their pigments. An algal bloom is the term that captures both the cause (quick algal growth) and the visible result (discolored, brown water). The other options don’t fit as well: sedimentation is about particles settling out, which would reduce cloudiness rather than cause a brown bloom; turbidity increase describes how muddy the water looks but doesn’t identify the biological surge; and the phrase “heavy populations effect” isn’t a standard scientific term for this phenomenon.