July 23, 2008 -- The Shenandoah River is a major tributary to the Potomac River, and it is an important source of drinking water for people in Virginia, Maryland, and the District of Columbia; however, severe fish kill events have been documented in this river and its tributaries since 2004. Theories abound as to the cause of the fish kills, and new proteomics analysis has helped to better explain the mortality rates.
A new study in the journal of Environmental Toxicology and Chemistry uses proteomics, the study of proteins expressed by a specific genome, to analyze the cause(s) of these events. Current environmental stressors include eutrophication, increasing temperature, and chemical contamination, and this watershed hosts many industries, such as rayon producers, the nation's top turkey-producing county, and pharmaceutical manufacturers, which together dispense at least 23 significant types of industrial contaminants.
Proteomics results from analysis of fish currently living in the river system show a particular impact on the immune system; metabolism, circulation, and respiration also have been affected. Because of the geographic extent, targets (mature adult fish), and variable responses, the fish appear to be affected by long-term exposure to sublethal toxic substances. In a four-month period in 2005, an 80% mortality of adult smallmouth bass and redbreast sunfish was observed.
Immunoglobulin proteins, which provide evidence of previous immune system challenges from sources such as bacteria and parasites, are elevated in all areas of the river tested (mainstem, North Fork, and South Fork), and higher leucocyte numbers in the mainstem and North Fork indicate either more vigorous immune systems or a response to greater immune system challenges. Judging by visible lesions and previous fish kill events, the latter is more likely. Fish from the South Fork locality show many of the same results as fish from the other two areas, but fish from the South Fork also show a complete absence of p40phox, which assists in respiratory burst responses and ultimately in cell metabolism and antioxidant defenses.
The combination of proteins that have been enhanced or suppressed suggests certain culprits, including arsenic exposure resulting from the poultry industry and fertilizer/herbicides from agricultural applications.
The study is "Utilization of protein expression profiles as indicators of environmental impairment of smallmouth bass (Micropterus dolomieu) from the Shenandoah River, Virginia, USA." The article appears in Environmental Toxicology and Chemistry, Volume 27, Issue 8, 2008, published by Allen Press.
Full text of the article is available at http://www.allenpress.com/pdf/ENTC27.8-8618-27-8-1756.pdf
Environmental Toxicology and Chemistry is a publication of the Society of Environmental Toxicology and Chemistry.
###
