People are helping Hood Canal suffocate, scientists find

People drawn to the beauty of Hood Canal are helping suffocate the very waters that brought them here.

Septic systems pumping nitrogen into the southern end of the deep, picturesque fjord, are helping feed a chain reaction resulting in fish kills and depleting the richness of underwater life, scientists announced today.

The findings follow three years of intensive work by scientists trying to decipher why the canal has suffered oxygen levels so low it killed thousands of fish in 2002, 2003, and again in 2006.

Nitrogen has long been blamed as the chief culprit, because it fertilizes algae growth. When the algae dies and decomposes, it sucks oxygen from the surrounding water.

But where, exactly, was the nitrogen coming from? And what can make things get so bad that beaches are repeatedly strewn with dead fish?

It turns out nitrogen flows into the canal from all directions — from the ocean, even from alder trees that suck nitrogen from the air, injecting it into the soil and water. Low-oxygen levels in the water can be triggered by a natural combination of weather and currents, evens when people aren't in the picture.

But now heavily populated areas delivered a critical dose of nitrogen during the most sensitive time, in some of the canal's most vulnerable areas, according to researchers.

People around the southern end of Hood Canal can have a big impact during the summer when oxygen levels reach their lowest, the scientists found. And that water could be helping to feed the fish kills in the Hoodsport area.

Human factors can cut oxygen in the water in the southern end by half, or more, during critical summer periods. Much of that comes in the form of nitrogen leaking from septic tanks, while some also comes from an increase in the alder population tied to logging.

For fish, that can make the difference between life and death.

Jan Newton, the University of Washington scientist leading the research effort, noted that when oxygen levels fall below 2 milligrams in a liter of water, rockfish start moving to avoid the water.

When it falls below .7 milligrams, it can kill the fish. Humans can cause as much as a 1 milligram drop in the lower Hood Canal during the summer, the scientists found.

The low oxygen is also tied to the growth of massive mats of white bacteria coating parts of the canal floor in the southernmost end.

U.S. Rep. Norm Dicks, who has helped steer federal money toward the research, said remedies will likely include costly new sewage systems for parts of Hood Canal.

"I think we're going to find that we have to put sewer systems in the lower hood canal. It's going to be expensive," he told people gathered in Bremerton today for a Hood Canal summit. "Now, I don't have any magical way to fund this."

Warren Cornwall: 206-464-2311 or wcornwall@seattletimes.com