Effects of Upwelling
Biodiversity and productivity
Because the deep water brought to the surface is often rich in nutrients, coastal upwelling supports
the growth of seaweed and plankton. These, in turn, provide food for fish, marine mammals, and
birds.
Upwelling generates some of the world’s most fertile ecosystems. A 25,900-square-kilometer
(10,000-square-mile) region off the west coast of Peru, for example, undergoes continual coastal
upwelling and is among the richest fishing grounds in the world. Overall, coastal upwelling regions
only cover 1 percent of the total area of the world’s oceans, but they provide about 50 percent of the
fish harvest brought back to shore by the world’s fisheries.
During El Niño, a weather phenomenon that typically occurs every three to seven years, the Pacific
Ocean’s climate changes dramatically. The transition zone between warm surface water and cold
deep water deepens. Trade winds are also weak during El Niño. The combination of weak winds and
deeper water limits upwelling. The reduction in nutrient-rich water leads to a lower fish population in
the area, and therefore to a smaller fish crop.
For the complete encyclopedic entry with media resources, visit:
http://education.nationalgeographic.com/encyclopedia/upwelling/
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Animal movement
Upwelling affects the movement of animal life in the area. Tiny larvae—the developing forms of many
fish and invertebrates—can drift around in ocean currents for long periods of time. A strong upwelling
event can wash the larvae far offshore, endangering their survival.
Coastal climate
The cold water welling up to the surface cools the air in the region. This promotes the development
of sea fog. The city of San Francisco, California, is famous for its chilly, foggy summers, brought on by
seasonal upwelling in the area.