Seasonality of E. coli and enterococci concentrations in creek water, sediment, and periphyton

Authors: STOCKER, MATTHEW - Orise Fellow; SMITH, JACLYN - University Of Maryland; HERNANDEZ, CAESAR - University Of Texas - El Paso; MACARISIN, DUMITRU - Food And Drug Administration(FDA); Pachepsky, Yakov

Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2019
Publication Date: 8/30/2019
Citation: Stocker, M.D., Smith, J.E., Hernandez, C., Macarisin, D., Pachepsky, Y.A. 2019. Seasonality of E. coli and enterococci concentrations in creek water, sediment, and periphyton. Water, Air, and Soil Pollution. 230(9):223. https://doi.org/10.1007/s11270-019-4263-1.
DOI: https://doi.org/10.1007/s11270-019-4263-1

Interpretive Summary: Fecal bacteria can indicate the possible presence of pathogenic microorganisms in irrigation, recreation, and other types of water. The presence of fecal bacteria is often related to the waste application and management practices in the areas close to the water source, and changes in those practices are called for or mandated. However, fecal bacteria can live and multiply in natural media contacting and affecting water, such as bottom sediment and periphyton, the latter being a thin layer of biological material covering submerged rocks. While knowledge was gained recently about the fecal bacteria in bottom sediments, nothing is known about the fecal bacteria in periphyton. The objective of this work was to carry out the first study showing the magnitude and seasonality of the fecal bacteria populations in periphyton. We studied a small creek and discovered concentrations of fecal bacteria in periphyton higher than in sediment and substantially higher than in creek water. This pioneer study is expected to stimulate research on the effect of periphyton on the microbial quality of water for irrigation and recreation.

Technical Abstract: Environmental reservoirs of fecal indicator bacteria (FIB) are attracting attention because of the complications they present when for the assessment of the microbial quality of water. FIB can survive and even grow in these reservoirs which means FIB measured in the water column may not have originated directly from a fecal source. Along with sediment, periphyton, i.e. aquatic biofilms growing on submerged rocks, have been shown to harbor large populations of FIB in the environment. Little is known about the spatial and temporal dynamics of FIB in periphyton. The objective of this work was to document levels of the common FIB, E. coli and enterococci, in creek periphyton during the summer and winter. FIB were measured in water, sediment, and periphyton during two summer and winter sampling dates at 5 sites along a 2.8 km stretch of creek in Beltsville, Maryland. Significant differences in FIB by site were only observed for E. coli in water at one time point. Levels of FIB significantly declined from summer to winter in all media. FIB concentrations ranged from 10^2 to 10^4 in the summer and from 10^0 to 10^4 CFU gdw-1 in the winter. When compared with the same unit of CFU gdw-1, periphyton contained higher concentrations of FIB than the sediment. Variability of FIB was in the order of water < sediment < periphyton. Levels of E. coli and enterococci measured in the same sample showed significant positive correlation in all media (Spearman correlation coefficients 0.87, 0.48, 0.70, for water, sediment, and periphyton, respectively). Results from this work show that fecal bacteria can persist in creek periphyton which may act as both a reservoir for fecal pathogens as well as a probably source of fecal bacteria to the water column.