What causes color variations in water?

• A. Suspended particles and dissolved materials
• B. Algae Blooms
• C. Water Temperature
• D. Salinity

Answer: (A)

Color variations in water come from what is in the water and how that material interacts with light. Suspended particles like silt, clay, and plankton scatter light and can reflect different colors, while dissolved substances such as organic matter (tannins and humic acids) and minerals absorb certain wavelengths, giving water colors that range from clear to blue, green, yellow, or brown. Algal cells contribute color through their pigments, especially during blooms, but that color arises from the same idea—substances in the water affecting light. Temperature and salinity can influence color only indirectly by changing how much dissolved material or how many organisms are present, not by directly deciding the water’s color. So the direct cause is the presence of suspended particles and dissolved materials.