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Chapter 6 : Physical and Biological Factors Influencing Environmental Sources of Fecal Indicator Bacteria in Surface Water
Category: Applied and Industrial Microbiology; Environmental Microbiology
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Early studies that examined the survival of fecal indicator bacteria (FIB) in water and their potential impact on water quality were focused on the influence of point source (sewage) contamination and dilution in the nearshore coast. Wave action is one of the primary means by which Escherichia coli and other enteric bacteria may be transported from distant source water to beach sand. Alderisio and DeLuca found that the potential impact of fecal coliforms from bird feces is not only related to the numbers and types of birds, but also to the duration and time of day that the birds roost on the surface water and their defecation rates. Microbial occurrence, survival, and growth in natural environments such as soil, sediments, and water are influenced by various physical, chemical, and biological factors, the extent of which may vary by environment. A section in the chapter addresses how environmental factors, such as temperature, moisture, predation, and competition, influence the population dynamics of FIB in the environment. A number of complex and often interrelated physical processes control the levels of FIB in nearshore waters including turbulent diffusion and dispersion, alongshore transport, dilution, advection, sedimentation, and resuspension. These physical processes control the distribution of FIB in recreational water, which influences estimates of nearshore beach water quality.
Schematic representation of the major pathways contributing to apparent FIB in surface water. The balance (i.e., net FIB) often represents the culturable bacteria recovered in water samples and does not account for their source(s).
E. coli populations within a 60-by-60-cm plot of forested top soil were eliminated to near extinction; within a few days, E. coli concentrations exceeded the original population and persisted for up to 5 weeks, ranging from log 2.4 to 4.8 CFU/g dry weight soil. Reprinted with permission ( Whitman et al., 2006 ).