Which zone is the deepest, dark, and experiences high pressure on the deep ocean floor?

• A. Profundal zone
• B. Aphotic zone
• C. Wetlands
• D. Abyssal zone

Answer: (D)

In the ocean, zones are defined by depth, light, and pressure. The abyssal zone is the deep-ocean floor region, typically around 4,000 to 6,000 meters below the surface. It is completely dark because sunlight cannot reach such depths, and the pressure is extremely high from the weight of the overlying water. The water is cold and organisms here must cope with these harsh conditions. This combination—great depth, total darkness, and high pressure on the deep ocean floor—fits the abyssal zone, unlike the profundal zone (a freshwater lake deep-water zone), the aphotic zone (any dark layer in the water column, not specifically the deepest ocean floor), or wetlands (terrestrial, not ocean floor).