What habitat occurs where freshwater meets seawater?

• A. Salinity
• B. Estuary
• C. pH
• D. Light

Answer: (B)

Estuaries are the transition zones where rivers meet the sea, so freshwater mixes with seawater to create brackish conditions under strong tidal influence. This blending creates a unique habitat with a salinity gradient, high nutrient input, and dynamic conditions that support diverse and productive communities, including many fish and invertebrate juveniles. The concept here is the distinct environment formed by the mixing of fresh and saltwater, which is what makes estuaries the correct choice. Salinity describes the level of salt in the water, pH is about acidity, and light is a resource that influences productivity but does not define a habitat in this context.