The effect of temperature oscillations and sediment texture on fecal indicator bacteria survival in sediments

Authors: SMITH, JACLYN - University Of Maryland; STOCKER, MATTHEW - Oak Ridge Institute For Science And Education (ORISE); Pachepsky, Yakov

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2019
Publication Date: 11/14/2019
Citation: Smith, J.E., Stocker, M.D., Pachepsky, Y.A. 2019. The effect of temperature oscillations and sediment texture on fecal indicator bacteria survival in sediments. Water, Air, and Soil Pollution. 230(11):270. https://doi.org/10.1007/s11270-019-4278-7.
DOI: https://doi.org/10.1007/s11270-019-4278-7

Interpretive Summary: The microbial quality of recreational, irrigation and other types of waters is evaluated by concentrations of fecal indicator organisms Escherichia coli and enterococci. These bacteria enter water sources via several pathways including flux from sediments. Survival of the fecal indicators in sediments is the important process to interpret the microbial water quality data. Such survival has been intensively studied, but the temperatures in all published to-date experiments have been kept constant, whereas diurnal oscillations are always present in natural conditions. The objective of this work was to find out whether and how temperature oscillations affect the survival of the fecal indicators entering sediment with manure. Experiments in microcosms showed that oscillations affect the survival in sandy sediments but not in clayey sediments. Both indicator organisms survived much better in clayey than in sandy sediments. Results of this work will be useful for researchers concerned with designing experiments on indicator organism survival, and for consultants using models to interpret the microbial water quality data and relate them to waste management in the vicinity of the fresh water source.

Technical Abstract: Fecal indicator bacteria (FIB) inhabiting stream sediments have become a concern with regards to recreational and irrigation water quality. Sediments contain higher concentrations of E. coli and other FIB than the overlying water column. The objective of this work was to evaluate the effect of temperature oscillations on the populations of both E. coli and enterococci in sediments and the water column. The study was conducted in a microcosm system with flow-through chambers representing a small stream with two different sediment textures. Bovine manure was freshly collected and mixed with both clayey and sandy sediment. Temperatures within the chambers oscillated from 17° to28°C which is representative of a diurnal summer temperature range for Maryland; the control chambers were kept at 22°C. The effect of temperature oscillation differed dependent on the sediment texture. Bacterial populations in the sandy sediment immediately increased before net die-off began. Conversely, in the chambers with the clayey sediments there was no immediate increase in concentrations in the oscillation chambers as compared to the controls. There was a significantly higher population of both E. coli and enterococci within the oscillation sandy texture chambers compared to the control constant temperature chambers; that was not the case in clayey sediment chambers. The die-off rates in the sandy sediments were greater than those in the clayey sediments; in the latter, bacteria populations remained almost constant throughout the experiment. Temperature oscillations should be simulated in experiments designed to estimate and compare inactivation rates for fecal indicator bacteria in sediments for future inferences on microbial water quality.