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Degradation Of Virginia Trout Streams Continues, Minor Recovery Also Indicated, Study Shows

October 25, 2000
University Of Virginia
Long-term quarterly monitoring of Virginia trout streams during a 12-year period indicates that acidification from "acid rain" is continuing, and generally worsening.

Preliminary findings from a survey conducted in April 2000 of 452 Virginia brook trout streams indicate some recovery from the acidification levels found in a 1987 baseline survey. The results, however, will require further analysis because they may be strongly influenced by differences in stream flow levels at the two separate points in time -- sampling in April 1987 took place under much wetter conditions than sampling in April 2000.

More importantly, long-term monitoring during the 12-year period -- using quarterly sampling of many of the same streams -- indicates acidification is continuing, and generally worsening, for most Virginia brook trout streams. Results of the quarterly monitoring also indicate that acidification may have caused biological harm to native brook trout.

"We have found that brook trout streams in Virginia are continuing to degrade," says Rick Webb, coordinator of the study and a research scientist in the Department of Environmental Sciences at the University of Virginia. "Our long-term monitoring provides little evidence of recovery."

The quarterly monitoring of trout streams -- and the larger 1987 baseline and 2000 followup surveys -- are part of the Virginia Trout Stream Sensitivity Study (VTSSS), a joint effort by several agencies and organizations to monitor chemical change, as a result of "acid rain," in acid-sensitive watersheds following enactment of the Clean Air Act Amendments of 1990. The amendments called for an approximately 40 percent reduction of sulfur dioxide emissions from coal-fired power plants by this year.

The VTSSS 1987 survey provided baseline data of stream conditions before enactment of the amendments. Followup surveys are used for comparison, to determine what changes have occurred. Quarterly monitoring -- which so far has covered 48 points in time -- provides the most reliable measure of change because it factors in numerous stream flow fluctuations. Stream flow levels can strongly influence water chemistry samples.

VTSSS was designed by environmental scientists at the University of Virginia and the ongoing analysis of data is conducted by those scientists. All of the streams surveyed are considered to be biologically and geologically representative of trout streams throughout the Virginia Appalachians.

Trout Unlimited, a national cold water fisheries conservation organization, provides partial funding for the project as well as numerous volunteers who help collect water samples.

Acid deposition, which is often called "acid rain," is the deposit of airborne acidic material from sources such as coal-burning power plants into streams, rivers and lakes as wet precipitation (rain, snow, fog, cloud) and dry precipitation (dust and gases). Acid deposition is responsible for the documented loss of hundreds of fish populations in Europe and North America.

The burning of fossil fuels release into the atmosphere sulfur and nitrogen oxides, which are converted to sulfuric and nitric acids. Coal-burning power plants in the Ohio River Valley are a major source of this pollution, which is carried east on prevailing winds.

Depending on the bedrock geology of a particular stream, these acids can create a situation that is deadly to fish. Acids release aluminum from the soil, resulting in an environment that is toxic to fish and aquatic insects. In surface waters at lower elevations, acids are usually neutralized because weathered bedrock has a buffering effect on acids that have entered streams and lakes. But at the higher elevations where brook trout live, the hard unweathered bedrock of headwaters has little buffering effect, allowing excessively high acidic conditions to develop. These acids accumulate over time, and even when the source of the pollution has been reduced, it may take years for the stream chemistry to respond. During that time the entire population of fish in a stream may become extinct.

"There is an apparent lag time in stream recovery," Webb says. "Our data show that stream quality is declining even as air quality has improved. Among 58 of the long-term monitoring streams for which 12 years of quarterly sampling data is available, acidity levels have decreased in only 15 streams. Acidity levels have increased in the rest."

According to Art Bulger, a U.Va. research scientist and one of the study authors, the hydrogen ion that is derived from sulfuric and nitric acids and the soluble aluminum create a poisonous combination for the fish. "The toxic action occurs at the gill, resulting in blood and body fluid disturbances leading to circulatory collapse. The fish basically has a heart attack," he says.

Of the three species of trout in the eastern U.S., the brook trout is the only native to the region, and is the most acid tolerant, Bulger says. Non-native rainbow trout and brown trout are more sensitive to acidification, and may experience greater declines due to this process.

VTSSS has received financial and other support from the U.S. Environmental Protection Agency, the National Park Service, the U.S.D.A. Forest Service, the Virginia Department of Game and Inland Fisheries, the Izaak Walton League of America, the Federation of Fly Fishers, as well as Trout Unlimited. The study authors include U.Va. scientists Rick Webb, Frank Deviney, Jack Cosby, Art Bulger and Jim Galloway.


For more information about the study, contact Rick Webb at (540) 468-2881 or (804) 924-7817. Leon Szeptycki, Trout Unlimited Environmental Counsel, can be reached at (703) 284-9411. Also visit: and

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Materials provided by University Of Virginia. Note: Content may be edited for style and length.

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University Of Virginia. "Degradation Of Virginia Trout Streams Continues, Minor Recovery Also Indicated, Study Shows." ScienceDaily. ScienceDaily, 25 October 2000. <>.
University Of Virginia. (2000, October 25). Degradation Of Virginia Trout Streams Continues, Minor Recovery Also Indicated, Study Shows. ScienceDaily. Retrieved April 14, 2024 from
University Of Virginia. "Degradation Of Virginia Trout Streams Continues, Minor Recovery Also Indicated, Study Shows." ScienceDaily. (accessed April 14, 2024).

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