Which statement about estuaries best describes them?

Which statement about estuaries best describes them?

• A. They are areas where freshwater and saltwater mix
• B. They are deep ocean basins
• C. They are arid desert regions
• D. They are mountain valleys

Answer: (A)

Estuaries are zones where freshwater from rivers meets and mixes with seawater from the ocean, creating brackish water whose salinity changes with tides and river flow. This mixing, along with nutrient inputs and tidal stirring, makes estuaries highly productive ecosystems and important nurseries for many species. The defining idea is the blending of fresh and saltwater. Other descriptions point to environments that aren’t estuaries: deep ocean basins are offshore and dominated by seawater; arid deserts are dry land with little marine influence; and mountain valleys are inland landscapes with different hydrologies.

Estuaries are zones where freshwater from rivers meets and mixes with seawater from the ocean, creating brackish water whose salinity changes with tides and river flow. This mixing, along with nutrient inputs and tidal stirring, makes estuaries highly productive ecosystems and important nurseries for many species. The defining idea is the blending of fresh and saltwater. Other descriptions point to environments that aren’t estuaries: deep ocean basins are offshore and dominated by seawater; arid deserts are dry land with little marine influence; and mountain valleys are inland landscapes with different hydrologies.