Lake Washington's ecosystem in trouble

As the research boat rocked gently on the waters of Lake Washington, Carla Geyer spooled out another 3 feet of cable. The well-used temperature probe continued its descent.

BACKGROUND

How changing water temperatures affect Lake Washington's ecosystem (Flash 6 required).

"Now 18.6," Geyer called out, reading the Celsius-calibrated gauge.

At a depth of 10 feet, the water is a few degrees cooler than room temperature. It's a tiny piece of the puzzle -- painstaking scientific measurements that are revealing a troubling trend.

For decades, Lake Washington -- the second-largest natural lake in the state -- was the region's toilet bowl. Billions of gallons of sewage were flushed into it. The foul flow didn't stop until the late 1960s, when local scientists had documented the environmental damage beneath the surface.

Now that same research, which continues today, is helping expose a new threat that isn't so easily averted.

No longer limited to glaciers melting in the Arctic, imperiled islands in the Pacific or even slushy ski slopes in the Cascades, evidence of global warming is turning up in Seattle's back yard.

Scientists from the University of Washington, tribes and state and federal agencies are documenting how the lake is changing in slight but potentially profound ways. The entire ecosystem is at risk: from zooplankton to prized salmon that use the lake as a summer home before heading upstream to spawn.

People can be affected, too. Climate change may be contributing to algal blooms, including a toxic variety that can trigger health warnings and beach closures.


		Paul Joseph Brown / P-I
	Off Madison Park Beach recently, UW research technologist Casey Ruff retrieves a device used to take samples of plankton from Lake Washington. Though the equipment is old, the collected research is offering insight into how the lake's life forms and temperature have changed over the past 50 years.

Between late spring and fall, the average temperature in the lake's 30-foot-deep top layer has climbed by more than 2 1/2 degrees Fahrenheit compared with readings taken four decades ago. The lake's overall average temperature has increased by 1 degree.

"It's only 1 degree, but it has huge effects," said UW researcher Monika Winder, who has published research on the warming trend.

Evidence of the new imbalance is mounting:

At the bottom of the food chain, some zooplankton -- barely visible organisms that devour algae and are, in turn, devoured by juvenile salmon -- are declining in numbers.
Rising temperatures are keeping the lake divided into warm and cool layers nearly a month longer than before, forcing some species of fish to seek refuge in lower depths where predators lurk.
Salmon are swimming an ever-more tropical gantlet from the Ballard Locks to the lake. New research shows that many of the sockeye traversing the locks later in the summer aren't surviving to spawn in the Cedar River. Last year, 200,000 sockeye -- half the return -- vanished before reaching the spawning grounds.

"This is going to alarm people," said Dave Seiler, a salmon scientist with the state Department of Fish and Wildlife, "but I think the story ought to come out."

Giant layer cake

Every spring, as temperatures rise and winds calm, Lake Washington settles into warm and cold zones like a giant layer cake.

During the past four decades, this stratified state has started weeks sooner and continued a little longer. The condition now lasts about four weeks longer -- 237 days last year -- triggering increasingly earlier bursts of algal blooms.

Daphnia -- star of the zooplankton world for its ability to chow through algae and keep the lake a sparkling blue -- hasn't been able to keep pace, said Winder, of the UW's School of Aquatic and Fishery Sciences.

The Daphnia population burst now lags behind the algal bloom, so other kinds of zooplankton are gobbling the plants before the Daphnia are around. In turn, the density of Daphnia in lake samples has dropped by more than half during the past 26 years.

"They are the critical link in the whole food web there," said Michael Brett, a UW environmental engineering professor.

Local researchers have tried to zero in on the cause of Lake Washington's warming trend. They've looked at the role of increased development raising temperatures as heat reflects off roads and buildings and escapes from auto tailpipes. They've considered fluctuations because of the effects of climate patterns, such as El Ni�o and other longer-term patterns.

But most think global warming is likely the largest engine driving the change -- particularly in the temperature increase seen during the summer.

There's evidence of other lakes warming too, including Lake Tahoe in California and Nevada, the Great Lakes and lakes in Europe and Africa.

"Warming has been seen in lots of different areas," said David Brakke, dean of the College of Science and Mathematics at Virginia's James Madison University. Scientists are still determining the effects.

"The changes could be quite profound," he said. "It can very radically change how the system is operating."

'This is out of whack'

There's a misty drizzle, but Ginny Merdes stands on her brick patio overlooking Lake Washington -- scanning the view for the millionth time.

"It's lovely out here," she declared.

For nearly 20 years, Merdes has lived on the lake's western shore, near Matthews Beach. Most summer days, the former newspaper editor swims in its waters.

Last year, though, bubbly, goopy, green algae invaded as never before. For weeks, the sludge clogged the water near her family's boat dock.

"Once it blooms, it's slimy," she said. "You could pick it up -- big handfuls of it. This is not some nice little thing floating around. It's like a mat."

One of Merdes' neighbors scooped it out with a pitchfork, spreading it on his garden like compost.

While this summer hasn't been as bad so far, Merdes points out the lime-colored islands taking hold between the sailboats and docks.

"All of us are going, 'What's going on?' " she said. "We were all thinking this is out of whack."

Another worrisome sign is a resurgence of blue-green algae in Lake Washington. Actually a kind of bacteria, some varieties can release toxins deadly to fish, pets and people. Blooms in Green Lake have triggered swimming bans and chemical treatments -- an impractical solution for a large lake.

Blue-green algae are making up a larger part of the algae population, the UW's Winder said. In late summer, they can be close to 60 percent of the algae in the lake.

Chunky green and blue-green algae can choke the filter-feeding zooplankton and are less nutritious for them than other foods. When the plants die, the algae sink to the bottom of the lake, where they rot and rob the water of oxygen important to fish and other deep-water dwellers.

When the lake is layered, this puts the squeeze on salmon from all directions. They're forced out of the upper layer when the temperatures get too hot, into the lower cooler layer where, for smaller fish such as juvenile sockeye, predators can be waiting. There's also less zooplankton -- a primary food for the smaller fish -- in the lower zones.

"These changes in the temperature just start affecting how much of the lake is accessible for feeding and dodging predators and all the stuff fish do," said Dave Beauchamp, a scientist with the UW and U.S. Geological Survey.

"You can affect which species are interacting with each other," he said. "They can have an entirely different food source or different predators that they're dealing with."

But first, the salmon have to get there.

Warming Ship Canal

For the past two summers, day after day, fish after fish, Jenny Newell and other scientists nabbed thousands of sockeye leaping up the Ballard Locks fish ladders.

The fish, which were returning from the Pacific Ocean, were held in a trough with running water as Newell tagged them behind their dorsal fin with a numbered disc.

"It's kind of like a gnarly piercing," she said.


	Karen Ducey / P-I
Yeun Chouaychath of Des Moines shows off a small mouth bass he caught while fishing from Seward Park on Lake Washington recently. Scientists have been conducting research to test the water and resident fish populations for toxins. The increase in the lake's water temperature is believed to have seriously affected sockeye salmon.

The fish were released into the Ship Canal upstream of the Hiram M. Chittenden Locks, the starting line for a trip through Lake Union, the Montlake Cut, Lake Washington and into rivers and streams to spawn.

Then from September to December, Newell went out to recover the fish. She floated down the Cedar retrieving tagged fish from shoreline rocks, weeds and underwater. She donned waders to slog through the smaller creeks on what amounted to a "very stinky scavenger hunt."

Alert fishermen, tribal members and other researchers returned discs that they came across.

When the tags were tallied, a surprising picture emerged. Fish swimming past the locks early in the summer -- before the temperature in the Ship Canal reached 70 degrees -- were recovered at twice the rate as the sockeye that had to brave temperatures better suited to people than salmon.

"As the temperature went up in the Ship Canal, our tag recoveries would go down," Newell said. "Maybe they're saying, 'Forget this, Lake Washington sucks.' "

Temperature readings from along the canal show a steep warming trend. In the 1970s, there were about 30 days a year that reached temperatures 70 degrees or higher. Twenty years later, the number of days had nearly tripled.

"For a fish biologist, it's a spooky-looking graph," said Seiler of Fish and Wildlife. Ideal temperatures for sockeye are closer to 59 degrees.

And in these warmer waters, more than 200,000 sockeye disappeared last year. About 400,000 were counted coming past the locks, Seiler said, but fishermen took only 70,000 of those, and 100,000 made it to the spawning beds.

It's not entirely clear what happened to the fish. Tribal scientists observed dead and struggling salmon in the Ship Canal. Others might have gone back to the Puget Sound.

"Maybe it's already too hot to have healthy sockeye," Seiler said.

The sockeye aren't native to Lake Washington. They were introduced in the 1930s, and their population is bolstered by a hatchery on the Cedar River.

Native chinook, a threatened species that also spawns in the Cedar, appear less sensitive to the change. But they also have been killed in the canal, apparently because of warmer temperatures.

"They got stuck in those areas, it was so hot," said Eric Warner, a biologist for the Muckleshoot Tribe. "They couldn't move much."

No easy fix

"Somewhere around here I should feel the bottom," said Geyer, still manning the temperature probe. The cable slackens.

"Two hundred feet and change."

The water's a cool 8.2 degrees (47 degrees Fahrenheit).

The spool of cable, secured with a bungee cord to a Lazy Susan, is wound back up. By hand. The equipment is decades old, like nearly all the scientific gear on the research boat -- really just a dinghy with an outboard and wooden benches.

Geyer and fellow researcher Casey Ruff are helping carry the torch for research that started more than 50 years ago, including taking plankton samples. The gear may be old, but it works well. Besides, Ruff said, new equipment would have to be calibrated to match the old to make the results comparable.

For decades, UW researcher Tommy Edmondson meticulously took the lake's pulse, watching it in the 1950s become increasingly choked with blue-green algae feasting on an all-you-can-eat sewage buffet.

"He just had such a wide-ranging curiosity," said Sally Abella, a King County scientist who worked for 30 years with Edmondson, who died in 2000. "He could get so excited about almost any issue around the lake."

The UW scientist was careful not to enter the fray over how to address the pollution. He left it to others to wield his research and win support for channeling the sewage into Puget Sound.

But he wasn't past taking bets on how the whole thing would turn out. When a distinguished Swiss scientist said it would take many years before the algae beat a retreat, Edmondson predicted a speedy recovery.

"Yes, he did win the bottle of Scotch," Abella said with a smile.

The lake's comeback was due mainly to the cleansing provided by the Cedar River, which was rerouted into the lake in 1916 to compensate for water lost to Puget Sound when the locks swing open and close.

"If you look at Lake Washington," said Brett, "it is probably the highest water quality of any lake surrounded by an urban area in the entire world."

But with the warming expected to continue, he added: "You always worry."

The path to solving today's warming-related woes is less clear.

Specific problems, such as the heat barrier created by the Ship Canal, could be addressed by catching salmon at the locks and transporting them to the lake. But the warming and longer-lasting stratification pose greater challenges. Operation of the Landsburg Dam on the Cedar and Ballard Locks can alter lake conditions, but the system is run to meet numerous demands for flood control and maintaining suitable river and lake levels.

Seattle Mayor Greg Nickels has led a charge to get other mayors to take action to reduce their cities' release of gases that help warm the atmosphere and switch to cleaner energy sources. State legislators this year approved a bill requiring cars in the future to be less polluting.

Merdes and other residents are making the link between changes in the lake and the warming climate.

"It's the beginning of awareness, at least for me," she said. "Hopefully, this is the beginning of people waking up and understanding and possibly doing something about it. Or at least getting our government to wake up and do something about it."

FACTS ABOUT LAKE WASHINGTON

Washington's second-largest natural lake (No. 1: Lake Chelan)
Contains enough water to cover Seattle to depth of 41.5 feet
Length: 13 miles
Average summer temperature: 58 degrees (top 30 feet)
Average clarity: 19 feet
Maximum depth: 214 feet
Key water sources: Cedar, Sammamish rivers
Water exchanged every 2 1/2 years
Fish species: about 40, including exotic species introduced after 1909 Expo
Most prevalent: three-spined stickleback; yellow perch; large-scale suckers; sculpin