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News Release

U.S. Department of the Interior
U.S. Geological Survey

Release: May 31, 2006
Tony Paulson (

John Clemens (

Scientists Go Deep to Track Algae-Feeding Nitrogen in Hood Canal

[Note: The USGS project Web page is]

Seawater flowing from Puget Sound into Hood Canal’s deeper layer has at least 17 times more algae-feeding nitrogen than all freshwater inputs combined, but how the deeper seawater circulates into the canal’s upper layer is not well understood, according to results of studies published today in a trio of reports by the USGS.

In the autumn of 2004, USGS scientists examined both saltwater and freshwater pathways of nitrogen into Hood Canal, including streams, rivers, ground water, and seawater flowing in from Puget Sound. Water samples were analyzed for nitrogen compounds to determine how much nitrogen comes into Lynch Cove at the southern end of Hood Canal and by what pathways. Scientists measured currents, temperature, salinity, dissolved oxygen, and nitrogen isotopes in the upper and lower layers of Hood Canal. They also found that at times the normal outflowing surface currents were reversed, pushing water in the upper layer back into Lynch Cove.

From these studies, USGS scientists estimate that 92 percent of the total freshwater load of dissolved nitrogen to the upper layer came from surface and ground water sources, with point-source and flow from shoreline septic systems contributing only 4 percent of the total freshwater load. In comparison, the nitrogen load in seawater flowing into Hood Canal from Puget Sound was at least 17 times the total freshwater load to the upper layer. Measurements of nitrogen isotopes in the upper and lower layers of Hood Canal, combined with observed conditions where the upper and lower layers meet, strongly suggests that nitrogen-rich water from the lower layer was mixed into the upper layer.

"Seawater flowing into Hood Canal is a double-edged sword," said Tony Paulson, USGS hydrologist and lead author of the main report. "Seawater currents flush out the system, but they also bring in enormous amounts of nitrate into Lynch Cove. However, we really can’t assess the human impact on Hood Canal until we can accurately model the very complicated movements of water, including complex effects caused by winds and by inflows of seawater from Puget Sound."

The USGS is working on Hood Canal with local groups and governments, agencies, tribes, and the University of Washington under the Hood Canal Dissolved Oxygen Program, enabled by funding secured by Congressman Norm Dicks. One goal of the program is to determine the pathways and quantities of nitrogen into Hood Canal. Excess nitrogen causes algae growth at the surface during late summer and early fall. When algae die off and settle to the bottom, their decay causes lethally low oxygen levels that kill fish and other species.

The report, "Loads of Dissolved Inorganic Nitrogen to Hood Canal and Lynch Cove, Washington," by Anthony J. Paulson, Christopher P. Konrad, Lonna M. Frans, Marlene Noble, Carol Kendall, Edward G. Josberger, Raegan Huffman, and Theresa Olsen,, is published as U.S. Geological Survey Scientific Investigations Report 2006-5106, and can be viewed on the Web at . A limited number of printed copies will be available by the end of June. To request a copy of SIR 2006-5106, send e-mail to

The report, "Surface-Water Quality in Rivers and Drainage Basins Discharging to the Southern Part of Hood Canal, Mason and Kitsap Counties, Washington, 2004," by L.M. Frans, A.J. Paulson, R.L. Huffman, and S.N. Osborne, is published as U.S. Geological Survey Scientific Investigations Report 2006-5073, and can be viewed on the Web at .

The report, "Transport Pathways in the Lower Reaches of Hood Canal," by Marlene A. Noble, Anne L. Gartner, Anthony J. Paulson, Jingping Xu, Edward G. Josberger, and Christopher Curran, is published as U.S. Geological Survey Open-File Report 2006-1001, and can be viewed on the Web at .

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