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Title:   Author  item
                                            Shelton, Danielitem
                                            Pachepsky, Yakovitem
                                            KIEFER, LYNDA - Bluewave Microbicsitem
                                            Blaustein, Ryanitem
                                            McCarty, Gregoryitem
                                            Dao, Thanh
  Submitted to: Water Research
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 4/8/2014
                                    Publication  Date: 4/18/2014
                                    Citation: Shelton, D.R., Pachepsky, Y.A., Kiefer, L., Blaustein, R.A., McCarty, G.W., Dao, T.H. 2014. Response of coliform populations in streambed sediment and water column to changes in nutrient concentrations in water. Water Research. 59:316-324.Interpretive Summary: The bacterium E.coli is commonly used as an indicator to evaluate the potential for microbial pathogenic contamination of surface waters. E. coli enter waters and bottom sediments via runoff or deposition from wildlife and/or farm animals. These E. coli typically die; however, rainfall events which result in nutrient runoff to streams can promote growth of E. coli in bottoms sediments.  This may affect the validity of using E. coli as indicator of microbial contamination. Very little is known regarding the effect of nutrient additions on the growth and survival of E. coli in water and sediment. In this study, we compared the die-off rates of E. coli entering stream sediments with bovine animal waste before and after nutrient additions to the water. The die-off rates were different. The nutrient addition resulted in E. coli growth both in water and in sediment, although growth in sediments was observed only at the highest nutrient concentration. Results of this work are important to researchers and practitioners in the fields of watershed management and irrigation in that it clearly indicates that growth of E. coli populations in sediments should be accounted for to correctly interpret microbial water quality monitoring data.
                                Technical Abstract: Aims: The focus of this work was to observe the response of water column and sediment coliform population to the change in nutrient concentrations in the water column. 
Methods and Results: The survival experiments were conducted in flow-through chambers containing sandy sediments. Bovine faeces were collected fresh and introduced into sediment. Sixteen days later, the same fecal material was autoclaved and diluted to provide three levels - 1X, 0.5X, and 0.1X of nutrient concentrations - spike in water column. Total coliforms, E. coli, and total aerobic heterotrophic bacteria concentrations were monitored in water and sediment.
Bacteria responded to the nutrient spike with initial growth both in the water column and in sediment. The response of bacteria concentrations in water column was nonlinear, with no significant changes at 0.1 and .5X spikes, but a substantial change at 1X spike. Bacteria in sediment responded to the spikes at all added nutrient levels. Coliform inactivation rates both in sediment and in water after the initial growth occurred, were not significantly different from the inactivationl rates before spike. 
Conclusion: These results indicate that introduction of nutrients into the water column results in nonlinear response of E. coli concentrations both in water and in sediments, followed by the inactivation with the same rate as before nutrients introduction. 
Significance and Impact of the Study: As sediments increasingly become recognized as reservoirs of indicator and pathogen microorganisms, understanding of the persistence of indicator organisms becomes important for assessment and predictions of microbial water quality.


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