What is a tidal pool?

What is a tidal pool?

• A. A shallow pool of seawater that forms on the rocky intertidal zone, home to various marine organisms
• B. A deep ocean trench
• C. A freshwater pond
• D. A flowing river

Answer: (A)

A tidal pool is a shallow pocket of seawater trapped in depressions on the rocky intertidal zone, formed when waves carve out basins and water remains after the tide goes out. This creates a tiny, isolated marine habitat that is sometimes covered by water, sometimes exposed to air, and experiences changing salinity, temperature, and oxygen as evaporation and rainfall mix with the seawater. Organisms living there must tolerate drying out and fluctuating conditions, such as seaweeds, barnacles, anemones, crabs, and small fish.

The other options describe very different environments: a deep ocean trench is a deep, offshore feature with high pressure and darkness; a freshwater pond contains non-saline water away from the coast; a flowing river involves moving freshwater, not a standing pool formed in rock.