Tiny organism could halt marina expansion | TahoeDailyTribune.com
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Tiny organism could halt marina expansion

Zooplankton, a one-cell organism, could bring Tahoe Keys Marina expansion to a standstill.

The story is long and convoluted, but environmental watchdogs have painted one villain: PAH.

PAH, or polycyclic aromatic hydrocarbons, are contaminates caused by the burning of fossil fuels, like coal and oil. When burned by motorized watercraft, PAH are believed to kill zooplankton, organisms at the base of Lake Tahoe’s food chain.



Zooplankton could stop the marina’s expansion if there is too much PAH in the water.

However, research on the negative effects of PAH on zooplankton and fish is preliminary.



None of the marina’s 150 proposed boat slips will be allowed if PAH exceeds 20 parts per trillion. If expansion begins and PAH increases despite efforts to limit the pollution, the marina will have to remove slips.

The threshold was established by James Oris, a Miami University professor and one of a handful of experts studying how PAH becomes more toxic when exposed to light.

He studied the effects of the pollutant in a tank of lake water on the North Shore in 1997. Oris said he tried to do experiments in the lake at the Tahoe Keys Marina last summer, but his equipment was vandalized.

Oris’ 1997 study showed how difficult pinpointing the sources of PAH in water can be. He found PAH moved from Tahoe City to two miles offshore within a 24-hour period.

Because PAH doesn’t dissolve readily in water and spreads out quickly, Tahoe Keys Marina co-owner Richard Horton said he’s worried excessive PAH levels will be blamed solely on his marina.

The Tahoe Keys Marina boats make up about a third of the water traffic in the Tahoe Keys. The Keys Property Owners Association and Beach and Harbor Association house 550 boats around the same lagoon.

Although the primary source of PAH in the water comes from boats, Oris said motorized vehicles, wood burning stoves, snowmobiles, restaurants that grill food and winds from highly contaminated areas deposit PAH in the water.

He said it would be impossible to eliminate PAH, and determining the effects of it in Lake Tahoe may be just as difficult.

Oris said it would take two more years of study to determine a safe PAH level for the entire lake.

He said the theory the contaminate has a negative effect on fish larvae and zooplankton can’t be fully supported until more research is performed.

According to his 1997 study, 100 percent of the fish and zooplankton in his tank were killed within 48 hours, when they were subjected to full sunlight and PAH concentrations of one part per billion.

In the absence of sunlight, Oris said certain PAH are known to hinder development, cause tumors and limit reproduction in aquatic life. However, Oris said those effects are found in water with higher concentrations of PAH than are present in Tahoe.

Studies of PAH in the lake will be performed at Tahoe City this summer by Oris, Glen Miller of the University Nevada Reno, and Brant Allen of the Tahoe Research Group.

Oris said PAH found in most U.S. surface waters, including Lake Tahoe, aren’t toxic to humans. PAH toxicity to humans mainly comes from areas with very polluted air, highly contaminated harbors, cigarette smoke or grilled food.

He said forest fires this summer will probably be a big PAH contributor.

Oris said discussion of PAH in regards to lake clarity is moot.

He said the decline in water clarity is related to nutrients, like phosphorous and nitrogen, entering the lake from erosion and runoff.

Oris said some environmentalists incorrectly related the lake’s clouding to PAH killing zooplankton and allowing algae to grow. Many justified the two-stroke boat engine ban in 1999 on this premise.

“As far as I can tell, PAH do not affect lake clarity at Tahoe,” Oris said. “PAH are a water quality issue.”


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