Phytoplankton Bloom off Vancouver Island

An explanation of the July 14 NASA MODIS Image of the Day, taken from spaceref.com:

Shown in this image, captured by the MODIS on the Aqua satellite on July 3, 2009, is the Pacific Northwest region of the United States and British Columbia, Canada.

In the upper left corner of the image is Vancouver Island.

Further south is (across from the left) Washington State, and south of Washington, part of Oregon. The bright green patches (one of which is right up against the southwestern shore of Vancouver Island

) are caused by millions of tiny ocean plants called phytoplankton. The coastal waters of the Eastern Pacific are productive because wind and ocean currents allow nutrient-rich water from deep in the ocean to rise to the surface. The cold, rising water carries phosphates and nitrates, which act as fertilizer to the phytoplankton

that grow in the sunlit waters at the ocean's surface. Since phytoplankton are the base of the food chain, areas that support large phytoplankton blooms tend to have large fish populations. Off the coast of Vancouver Island and Washington State, phytoplankton blooms tend to happen when winds blow down the coast from the north. The winds push the ocean's surface water west, out to sea. Deep water rises up to replace the wind-blown surface water, and it carries the nutrients needed to support phytoplankton blooms.