PADI Divemaster Certification Practice Exam

Why are areas with coastal upwellings considered highly productive?

1. They have clearer water

2. They receive abundant sunlight

3. They bring nutrients to the surface

4. They have higher temperatures

The correct answer is: They bring nutrients to the surface

Areas with coastal upwellings are considered highly productive primarily because they bring nutrients to the surface. Upwelling occurs when deep, cold, and nutrient-rich water rises to the surface, replacing the warm, nutrient-depleted water. This vertical motion of water is often driven by winds blowing along the coastline and helps to nourish phytoplankton, which form the base of the marine food web. These nutrients, such as nitrates and phosphates, are essential for the growth of phytoplankton, which serve as food for a variety of marine organisms, including zooplankton, fish, and larger marine animals. As a result, areas with coastal upwellings typically support rich biodiversity and high fishery yields, making them vital regions for commercial fishing and marine ecosystems. While clearer water, abundant sunlight, and higher temperatures can also play a role in marine productivity, they are not the primary reason why upwelling zones are so fertile. Clearer water can sometimes indicate lower productivity, while abundant sunlight and higher temperatures alone do not necessarily equate to higher biological productivity without the availability of nutrients.