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New Research explains Rich Puget Sound Waters

Apr 14, 2014 12:02 PM EDT

A new study may help explain why the famously rich waters of the Puget Sound are able to support such an abundance of life, including shellfish, salmon runs, and occasional pods of whales.

Oceanographers at the University of Washing have made the first detailed measurements at the headwaters' source - a submarine canyon offshore from the strait that separates the US and Canada and draws up nutrient-rich water from the deep ocean. Their observations reveal water surging through the canyon and mixing at high rates with the waters above, according to a release from the school.

"This is the headwaters of Puget Sound," said Parker MacCready, a University of Washington oceanography professor and co-author of the study that originally appeared in Geophysical Research Letters. "That's why it's so salty in Puget Sound, that's why the water is pretty clean and that's why there's high productivity in Puget Sound, because you're constantly pulling in this deep water."

The intense flow and mixing measured inside the canyon could help explain the mysterious productivity of northwest shores. While nutrient movement up the West Coast is generally attributable to coastal winds, those numbers do not hold true for the northwest Pacific region.

"Washington is several times more productive - has more phytoplankton - than Oregon or California, and yet the winds here are several times weaker. That's been kind of a puzzle, for years," said co-author Matthew Alford, an oceanographer with the University of Washington's Applied Physics Laboratory.

MacCready and Alford took their measurements from the Juan de Fuca Canyon and showed water flowing as fast as 1.3 feet per second at 500 feet below the surface and mixing at up to 1,000 times the normal rate for the deep ocean.

University of Washington oceanographer Barbara Hickey first suggested the idea that the northwest's outsize productivity could be marine canyons. There are 11 such canyons along the Washington coast, more than either coastal region of Oregon or California. The deep water forced up through the canyon is rich in nutrients that support the growth of marine plants, which then feed other marine life.

"The location of this sill would be an outstanding place to fish," Alford said. "People fish in Juan de Fuca Canyon pretty actively, and that's probably no coincidence."

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