Why are large numbers of ocean animals found in areas where upwelling occurs?

Upwelling waters occur when the warm water, on the surface of the oceans in the equatorial regions are pushed towards the poles by winds and the denser cold currents on the ocean bottom move up to replace the displaced waters. The denser currents are usually nutrient-filled and are an ideal substrate for growth of phytoplankton as they warm up on the surface. The algae bloom attracts fish and other producers in the sea. The producers consequently attract other carnivorous fish.