What is the cause of the red color of the waters around Madagascar?

• A. Algae blooms
• B. High iron content
• C. Sediment from rivers
• D. Soil runoff in ocean

Answer: (D)

When water color changes along a coast, think about what is suspended in the water. The red tint around Madagascar mainly comes from soil and sediment washed into the sea by rivers and runoff. Those fine particles—clay and silt, often rich in iron oxides—scatter and reflect sunlight in a way that makes the water look reddish. This explanation focuses on land-derived material entering the ocean, not on pigments produced by organisms. Algae blooms can color water too, but they usually give greens or different hues and are tied to nutrient conditions and the presence of living organisms. Broad red coloring from runoff is a straightforward, consistent cause, so soil runoff in the ocean best explains the red waters observed.