The central coast of California is one of only five regions in the world where major upwelling occurs. Cold, nutrient-rich water is driven to the surface as a result of wind, the angle of the coastline, and the rotation of the earth. The cold, deep water is filled with nutrients and during the spring when the northwest winds blow, this rich water is brought to the surface, fueled by the sun, and creates surface plankton blooms.
Plankton form the base of the food chain for all marine animals.
Whales, dolphins, and seabirds concentrate in the waters off central California to feed on an abundance of krill, fish, and squid supported by these intense plankton blooms. This extremely nutrient-rich area is centered around the Monterey Submarine Canyon which runs through the middle of Monterey Bay. During the winter and spring months the entire gray whale population migrates through the Sanctuary within three kilometers of the Monterey Bay coastline, traveling to their summer feeding grounds in the Bering Sea and to their winter breeding grounds in Baja. Gray whales are rarely seen feeding in central California. Gray whales, especially calves, fall prey to killer whales and these events sometimes occur within the Sanctuary.