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Fish kills still a mystery, DEQ says
By Anne Adams • Staff Writer
HOT SPRINGS - Last year, state biologists took to the waters here, searching for explanations as to why fishwere turning up dead and diseased. And while several causes have been ruled out, no one thing has been found as the culprit.
State officials with Virginia's Department of Environmental Quality and Department of Game and Inland Fisheries coordinated their studies of fishmortality in the Shenandoah, James, and Cowpasture rivers in 2007.
They looked at the chemistry in the water and sediment, water temperatures, the presence of heavy metals, and other potential factors, but nothing turned out to be the smoking gun.
Don Kain, water monitoring and assessment manager at DEQ's Valley Regional Office,says the investigation will continue this year. "Unforunately, we cannot project a specific timetable for the length of the fishkill investigation," he told The Recorder Wednesday. "Our hope, of course, is that the answer(s) will become evident following completion of the current studies. It is more likely, however, that the data from 2008 will help us eliminate more 'suspects' and direct a more intense focus toward others. For the foreseeable future, my expectation is that DEQ and DGIF will keep up the study as long as is necessary."
In the DEQ's summary report issued April 24, the research was explained.
Water and sediment chemistry
• Conventional pollutants - DEQ monitored weekly for conventional pollutants from March through August 2007 at 12 sites. These pollutants included things like nitrate, ammonia, and suspended solids. "All results were within normal ranges or, where water quality standards exist, they were below those threshold values," the report states.
Also, DEQ recorded pH, temperature, dissolved oxygen, and conductivity at six sites every 15 minutes from the end of March through August 2007. "Results showed high variability in daily pH measurements … a large swing, but similar pH shifts have been seen in other Virginia waters with no associated fishkills; also some sites where fishkills occurred had relatively small daily swings of less than 1 pH unit. Therefore, pH changes do not appear to be related to the fishkills," DEQ said. "Dissolved oxygen does not seem to be a factor in the fishkills. Levels were acceptable at all sites during the spring period (when fishkills occurred). Low dissolved oxygen levels occurred in the North Fork Shenandoah River at Cootes Store when the water flows dropped and temperatures increased in July and August, but there were no fishkills at that time."
Temperatures in the water, DEQ said, seem to be related to the timing of the fishkills, which stopped when temperatures reached about 75 degrees.
Studying the chemistry in the water, DEQ determined the areas where fishdied had a diverse number of chemicals, and their levels were largely indicative of an agricultural area. "Chemicals such as PCBs, pesticides, PAHs, and pharmaceutical compounds were found, but results were not inconsistent with other developed areas that have not experienced fishkills," the report said. "No individual chemical compounds were found at levels that by themselves would indicate a clear cause of observed fishmortality."
Toxicity in the water was also tested at four sites in the Shenandoah River by the Environmental Protection Agency. All four sites in March 2007 had "significanteffects on survival," the report explained.
"EPA scientists suspected that a pathogen may have been interfering with the tests, so sampling was repeated during the week of May 14. The South Fork Shenandoah River water did not have any significanteffect on survival or growth in the follow-up tests. Water from the remaining three sites all had significanteffects on survival. When water from North Fork Shenandoah River and Cedar Creek was disinfected with ultraviolet radiation, however, there was no significanteffect on survival or biomass. It appears that the outcome of these tests could have been more strongly influenced by a biological pathogen than chemical constituents in the water."
Sediment metals
Sediments were sampled at North Fork and South Fork Shenandoah River sites, and sites in the South, North, Maury, and Cowpasture Rivers, DEQ said, for heavy metals and arsenic. "No samples had concentrations in excess of levels that would be expected to have effects on growth or survival in fish," they reported. "Metals tested for included arsenic, copper, cadmium, nickel, zinc, lead, and mercury."
Storm monitoring
With citizen volunteers, DEQ kept collecting water samples to test for ammonia and other things during storms from March to June last year. Levels were found below chronic or acute toxic concentrations for fish, DEQ said.
And, metals tests analysis showed "that all metals were detected below levels expected to cause death or sub-lethal effects in fish."
Nutrients
Virginia Tech has been conducting a multi-year study of benthic invertebrates in fishkill waters and reference streams since 2006, DEQ said. "Initial findings confirmthat the fishkill areas in the Shenandoah system are indicative of a nutrient-rich environment, a common condition in rivers of this size, but there is no indication of any invertebrate taxa being eliminated due to toxic compounds … field work focusing on local land use influences on invertebrates and water chemistry in tributary streams was initiated, along with responses of selected organisms to laboratory chemical exposures."
What will they study this year?
Kain said topics to look at in 2008 will include:
• Measuring snail density and rates of parasitic infection, determining relationships of these measurements with environmental stressors/ land use
• Identifying trematode parasites using the snail as an intermediate host, further investigation of the relationship of observed snail responses and land use, and investigation of the effects of specific stressors on snail respiratory, immune, and reproductive systems.
Fish viruses
According to the DEQ's report, "Virus testing was conducted last year by the U.S. Fish & Wildlife Service and Cornell University. No known fishviruses were found in numbers sufficientto account for the fishkill events.
"A small percentage of Virginia fishkill samples tested positive for Largemouth Bass Virus (LMB-v); the low rate of incidence suggests it is not a cause of the fishkills, although it may further compromise the health of infected fish. Also, bacterial assays were conducted by the U.S. Geological Survey and the USFWS. A number of indigenous, opportunistic bacteria were cultured from skin, lesions, and gills of fishfrom both fishkill and non-fishkill sites, DEQ said. "These organisms are considered part of the normal bacterial flora, and typically only cause infection in already compromised hosts. In addition to normal bacterial flora, fishfrom sites experiencing fishkills showed unexpectedly high numbers of two obligate pathogens ... known to be capable of functioning as primary pathogens, that is, they can be the causative agent of fishdisease. These organisms were found at active fishkill sites ... A follow-up study on bacteria by USGS is under way in 2008."
USGS researchers noted high parasite loads externally and in gills, livers, kidneys and spleens of fishfrom the fishkill areas, DEQ explained. "These parasites may weaken fishand increase their susceptibility to disease. Many of these parasites have intermediate hosts, such as snails, zooplankton, and benthic invertebrates, all of which may be found at higher densities in nutrient enriched waters. This link is being explored further." In addition, the agency said, USGS say smallmouth bass and sunfishare stressed populations which succumb to a variety of pathogens and parasites when stressed beyond their tolerance. "Evidence includes:
• Gill lesions, suggesting that ammonia, diatoms, or other irritants may be leading to respiratory problems.
• Massive proliferation of internal parasites in bile ducts, leading to destruction of large portions of the liver.
• Macrophage aggregates in a variety of internal organs - increase in response to both infectious agents and contaminants.
• Moderate to high incidence of intersex in male smallmouth bass, suggestive of exposure to estrogenic compounds."
What's next?
All the studying seems to have ruled out water quality and likely fishviruses, but DEQ says more research will continue on things like:
• Effects and relationships of combinations of water quality constituents - "Even though no individual constituent appears responsible for the fishkills, how might different combinations of chemicals behave? Are combinations of chemicals additive? Synergistic? Could they have secondary effects as stressors? What differences exist between the rivers experiencing fishkills and rivers with no kills?" DEQ will explore.
• Biological pathogens - "Further work is needed to determine if organisms such as the bacterium Areomonas salmonicida are functioning as primary pathogens," the report states. "Are there other bacteria or viruses that have not yet been identified?
• Fish health - Additional measurements of tissue and histology, blood chemistry, hormones, organ function, and infestation and role of parasites are needed, the report said. "Sample sizes must be adequate for statistical comparisons between sites, species, age groups, and sex of specimens. Sufficientnumbers of specimens need to be collected from reference streams and fishkill areas. Do the fishresponses such as intersex have a bearing on fishkills? Are measurable, sublethal effects occurring in other members of the aquatic community, such as benthic macroinvertebrates?"
Only more research will ultimately get closer to explaining the problem, DEQ says.
Kain will speak at a meeting of the Cowpasture River Preservation Association in Clifton Forge this Saturday, May 3. Citizens are welcome to attend Kain's presentation.
It begins at 7 p.m. at Lone Start Advent Christian Church. For more information, contact Caroline Bott at directorcrpa@ gmail.com, (540) 460-0268.
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