Which factor affects water color due to organic matter?

The correct answer highlights that algal growth significantly influences water color due to the presence of organic matter. Algae, especially in high concentrations, can impart a greenish hue to the water as they proliferate. This phenomenon occurs when the conditions are favorable for algal blooms, which often thrive in nutrient-rich environments.

When organic matter is present in water, it can lead to increased nutrient levels, particularly nitrogen and phosphorus. These nutrients support algal growth, and as algae multiply, they can change the water's visual characteristics. The color of water can vary widely depending on the type and density of algae present, ranging from green to brown or even red.

In contrast, other factors such as oxygen levels, temperature changes, and nutritive elements can influence water quality and aquatic life but do not directly affect the color of water as prominently as algal growth does. Therefore, understanding the connection between algal blooms and water color is crucial for monitoring and managing water quality. This relationship is essential for those in the water treatment and management fields, particularly when assessing the ecological health of bodies of water.