Galicia has productive coastal waters because upwelling regularly brings cold, nutrient-rich water toward the surface, where it can support phytoplankton growth and the wider food web. This productivity helps sustain shellfish, fish, seabirds, and marine mammals, and is one reason the Galician coast is so biologically active.
Coastal upwelling is the process by which winds push surface water away from the coast and deeper, colder, nutrient-rich water rises to replace it. On the Galician coast the usual wind is northerly, and the process is most active from spring through summer. The rising water cools the surface, supplies nutrients to phytoplankton, and helps explain both cold summer water and high marine productivity along this Atlantic shelf.