Thursday, April 9, 1998 | 8:33 a.m.
James Oris, a scientist at Miami University in Ohio, said tests conducted last summer appear to show that exhaust from boats and personal watercraft are damaging fish larvae and zooplankton - vital links in Lake Tahoe's food chain.
"There was a measurable toxicity to fish and zooplankton," Oris told the Reno Gazette-Journal. "Basically what we found was there appeared to be levels of phototoxic materials in the lake that could be detected, and those levels appeared to be related to watercraft activity."
The study was paid for by the National Marine Manufacturers Association. The trade group is fighting plans by the Tahoe Regional Planning Agency to ban two-stroke engines that power Jet Skis, Sea-Doos and other popular personal watercraft from Lake Tahoe.
John Fagan, a lawyer for the association that represents boat and personal watercraft makers, said the scope of Oris' work is too limited to draw firm conclusions.
"One thing is clear. The results are inconclusive," he said.
Oris' study is to be released next week during an environmental toxicology conference in France.
TRPA officials said that while preliminary, Oris' study is extremely important.
"This is a critical thing," said Gordon Barrett, a chief planner with the TRPA. "This is important information that needs to be expanded upon."
Oris and colleagues took water samples last year at the edge of the no-wake zone off a marina at Tahoe City, Calif., and at another location two miles offshore.
The water was then placed in tanks for toxicity tests using zooplankton and fish larvae.
Those organisms exposed to sunlight showed ill effects that can occur when sunlight reacts with hydrocarbons animal tissue absorbs, Oris said.
He said one test indicated a 46 percent decrease in fish growth, and a significant number of zooplankton was killed during both one-week experiments.
Oris said a correlation also was found between peak boating activity and concentrations of hydrocarbons in the water.
"It's an indication of a potentially significant impact," he said.
Oris and TRPA officials agree that more tests are needed to determine the magnitude of the problem and define the risk to Lake Tahoe's aquatic life.
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