Year: 2009
Type: dissertation
Abstract: Enterococci are fecal indicator bacteria (FIB) that are used worldwide for water\nquality assessment. However, evidence of high densities and extended survival of\nenterococci in sediments and submerged aquatic vegetation (SAV) has caused uncertainty\nabout their reliability in predicting human health risks from recreational activities in\nenvironmental waters. To address the concern that sediments and SAV may harbor large\nreservoirs of enterococci that can affect water column concentrations, aquatic mesocosms\nand environmental sampling were employed to investigate patterns of enterococci\ndensities and population structure across the Tampa Bay watershed.\nIn mesocosm experiments and environmental samples, SAV harbored higher\ndensities of enterococci, per mass of substrate, than sediments, and sediments harbored\nhigher densities than water. Population structure assessed by BOX-PCR genotyping was\nrelatively unique in each sample, although slight similarities among samples suggested\ngrouping primarily by location rather than substrate or season. Strain diversity was\nhighly variable, and many samples had low diversity, including nearly monoclonal\nstructure throughout the mesocosm experiments and in several of the environmental\nsamples. Several strains were highly abundant and cosmopolitan (found across sites,\nseasons, and substrates), and may represent highly naturalized and reproducing indicator\nbacteria populations that are not directly related to pollution events.\nWhen the enterococci densities were viewed from the perspective of the entire\naquatic system, SAV-associated enterococci did not comprise a major proportion of the\ntotal population, due to the typically large differences in volume of each substrate (SAV\nvs. sediments vs. water). Instead, the largest proportions of enterococci were typically\nfound in the water or the sediments, depending on the relative volume of substrate or the\nenterococci density associated with each substrate. Modeling results illustrate that the\nrelative importance of each substrate in terms of FIB populations can shift dramatically\nover time and space due to changes such as vegetation cover, tidal cycles, and bacteria\ndensities. Furthermore, at several sites within the watershed, estimates of sediment and\nbacteria resuspension from sediments were very low, suggesting that this process rarely,\nif ever, significantly affects water column concentrations of enterococci in the watershed.
Author: Brian D. Badgley
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W76724583