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Fecal material also contains nutrients and organic matter. Nutrient addition to surface waters, particularly phosphorus and nitrogen, can increase algal growth, decrease water clarity, and increase ammonia concentrations which can be toxic to fish. The increased organic matter also serves as a food source for bacteria and other microorganisms, resulting in lower oxygen levels in the water, and often no oxygen in deeper bottom waters.
In the Middle River watershed, the source of E. coli contamination is felt to be primarily due to livestock. Augusta County has the second greatest number of cows in Virginia and is the leading beef cattle, sheep and lamb producer. It is also one of Virginia’s largest poultry producers.
A riparian buffer is the area of trees and other vegetation along a river that serves to protect these waters from agricultural runoff. The larger the buffer, the better. Riparian buffers filter out pathogens, absorb nutrients and block sediment and other contaminants like pesticides from reaching the river. The presence of E. coli is a strong indicator that the riparian buffers along a river are not adequate and/or that livestock have direct access to the river.
E. coli monitoring gives us a broad understanding of a river’s health.
~ Tom Shapcott, 2020 E. Coli Committee Chair
E. coli is short for Escherichia coli. This is a type of bacteria commonly found in the intestines of animals and humans. The presence of E. coli in water is a strong indication of animal waste or human sewage contamination each of which may contain many types of disease-causing organisms.
E. coli may be directly deposited in our waters by animals or humans. But, also, during rainfalls, snow melts, or other types of precipitation, E. coli may be washed into creeks, rivers, streams, lakes, or groundwater.
Although most strains are harmless some strains may produce a powerful toxin and can cause severe illness. So, even though E. coli in water may not be directly harmful itself, it does indicate an increased likelihood of other harmful pathogens (disease-causing microbes) in the water.
Scientists use the presence of E. coli as an indicator to monitor for the potential presence of more harmful microbes such as Cryptosporidium, Giardia, Shigella, and norovirus. Pathogens often co-occur with indicators of fecal contamination. Because it is not feasible to test waters for each possible type of disease-causing bacterium or parasite, fecal indicator bacteria such as E. coli are sampled to indicate the statistical likelihood of contracting a disease by ingesting or recreating in waters.
Extensive studies have demonstrated that E. coli concentrations are one of the best predictors of gastrointestinal illnesses associated with swimming in untreated surface waters. However, what is considered the “safe” E. coli level in water bodies is much debated.