Areas where colder, nutrient-rich, and biologically productive subsurface waters are brought to the surface. Phytoplankton thrives in these conditions and are at the base of the oceanic food chain. Therefore these are the biologically most productive areas. A combination of winds, currents, the Earth's rotation, shorelines and shallow bottoms induces upward and downward water movements. There are coastal upwellings as well as equatorial upwellings.