Birds, fish test positive for mercury at Walker Lake

Sunday, Feb. 28, 1999 | 9:13 a.m.

Mercury was detected in near-lethal levels in three common loons captured last year at the desert lake 120 miles southeast of Reno. Two other loons had elevated levels of mercury.

Tui chub, the birds' primary food source at the lake, also appear to have high levels of mercury, according to samples of the fish taken in 1996.

"We're beginning to get a feel that there might be a problem," said Stan Wiemeyer, contaminant specialist with the U.S. Fish and Wildlife Service. "We need more information before we can say how severe it is and what we might be able to do about it."

The Nevada Division of Wildlife next month plans to test Lahontan cutthroat trout at the lake for mercury. The native trout is the lake's only game fish.

If high levels of mercury are detected, the state will issue a health advisory warning people not to eat the trout. A similar advisory is in effect for fish caught in Lahontan Reservoir on the Carson River.

Scientists originally thought the loons picked up the mercury in their wintering grounds in Mexico. Hundreds of migrating loons stop at Walker Lake every spring and fall.

But scientists then detected mercury in the tui chub, whose movements are restricted to the lake.

"It (contamination) is there, in the Walker River system, and it had to get there somehow," said Mike Yates, a Boise State University biologist who's researching the problem.

The mercury could have originated from numerous defunct gold mines in the watershed, Yates said, adding mercury was used to remove gold and silver from ore.

Wiemeyer speculated that high Walker River flows in recent years could have stirred up mercury-laden sediment. That would explain why mercury levels in the lake's tui chub were five times higher in 1996 than 1994, he said.

But Joe Tingley, a geologist with the Nevada Bureau of Mines, said he'd be surprised if past mining activity is the culprit. Most of the mines were small and located too far away, he said.

A more likely source is the old U.S. Naval Ammunition Depot near Hawthorne, Tingley said. During World War II, the military used Walker Lake for target practice with mercury-laden bombs, he said.

Yates said the loons also may have picked up some mercury in their wintering grounds. Further tests will be conducted to pinpoint the source of the mercury, he said.

An effort is under way to buy water rights for the troubled lake, whose water volume now is less than one-fourth of what it was in 1908.

Five straight wet winters have given Walker Lake a reprieve, but researchers acknowledge that more Walker River must reach the lake to sustain life in it.

Two-thirds of the river water never makes it to the lake because of upstream reservoirs and agriculture.