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The Honolulu Advertiser
Posted on: Tuesday, April 17, 2001

Oceanic eddy swirls for eight months

By Jan TenBruggencate
Advertiser Science Writer

For eight months ending in January 2000, an oceanic eddy swirled in the waters southwest of the Islands, bringing nutrient-rich cold water up from the depths and generating a cycle of fertility that brought fish in from miles around.

A Web site image shows the location of an oceanic eddy southwest of Hawai'i. The eddy provides a nutrient-rich environment for fish.
The churning of the ocean waters was caused by the current flowing with the tradewinds through the 'Alenuihaha Channel between Maui and the Big Island.

Loretta, as scientists called the phenomenon, wasn't unusual in its appearance or location, but for its duration.

"Eddies naturally occur in this locale for periods of several weeks to a few months, but Loretta persisted for eight months according to satellite data," said University of Hawai'i researcher Bob Bidigare.

Satellites made note of the temperature difference and found the water in the middle of Loretta was colder than outside the eddy.

They also noted the change in the color of the eddy water. The nutrient-rich water promoted the growth of phytoplankton. Heightened chlorophyll levels from the phytoplankton change the color of the water slightly.

Loretta's color was viewed using NASA's SeaWiFS Satellite. The GOES-10 weather satellite was used to measure the temperature.

The increased levels of phytoplankton, which are near the bottom of the food chain, set up a nutrient-rich situation for fish — and a boon for anglers.

The study was published in Geophysical Research Letters. It was written by Michael Seki of the National Marine Fisheries Service, with Bidigare and Carrie Leonard of the University of Hawai'i, Jeff Polovina and Russell Brainard of the fisheries service, and David Foley of the Joint Institute of Marine and Atmospheric Research at Manoa.