Which area of the ocean is typically richest in nutrients?

• A. Open ocean (pelagic zone)
• B. Coastal upwelling zones
• C. Abyssal plain
• D. Coral reefs

Answer: (B)

Verified step by step guidance

1. Understand the concept of nutrient distribution in the ocean: Nutrients in the ocean are often concentrated in areas where water movement brings them to the surface or mixes them into biologically active zones. Coastal upwelling zones are particularly important for nutrient cycling.
2. Define 'coastal upwelling zones': These are areas where deep, nutrient-rich water rises to the surface due to wind-driven movement of surface water away from the coast. This process replenishes nutrients in the photic zone, supporting high biological productivity.
3. Compare the nutrient levels in the listed zones: The open ocean (pelagic zone) generally has low nutrient levels due to limited mixing of deep water. The abyssal plain is nutrient-poor because it is far from sunlight and biological activity. Coral reefs are nutrient-rich but rely on localized recycling rather than large-scale nutrient influx.
4. Explain why coastal upwelling zones are the richest in nutrients: The upwelling process brings nutrients from the deep ocean to the surface, where they can be utilized by phytoplankton and other organisms, leading to high productivity and supporting diverse ecosystems.
5. Conclude that coastal upwelling zones are the correct answer based on their unique nutrient cycling mechanism and biological productivity compared to other oceanic zones.