Citation:

Li, X., L. Peed, Mano Sivaganesan, C. Kelty, C. Nietch, AND O. Shanks. Evidence of Genetic Fecal Marker Interactions between Water Column and Periphyton in Artificial Streams. ACS Omega. American Chemical Society, Washington, DC, 3(8):10107-10113, (2018). https://doi.org/10.1021/acsomega.8b01785

Impact/Purpose:

Periphyton is a complex mixture of algae, microbes, inorganic sediment, and organic matter that is attached to submerged surfaces in most flowing freshwater systems. This community is a key component of stream ecology and is also known to absorb pollutants from the water column, resulting in improved water quality. However, it remains uncertain what the role of periphyton is in the fate and transport of genetic fecal indicators suspended in the water column. An indoor mesocosm study was conducted to simultaneously measure genetic fecal indicators in the water column and in the associated periphyton when subject to wastewater point source loading. The experiment was conducted over 16-weeks and organized into periphyton colonization and wastewater loading periods. Treated waste water effluent was pumped directly from a treatment facility adjacent to the experimental stream facility. Inflow and outflow surface water grabs were paired with the collection of periphyton samples taken from the mesocosm substrates on a weekly basis. Samples were analyzed with three genetic fecal indicator qPCR assays targeting E. coli (EC23S857), enterococci (Entero1), and Bacteroidales (GenBac3), as well as, two human host-associated fecal pollution markers (HF183 and HumM2). In addition, periphyton dry mass was measured. During wastewater effluent loading, genetic markers were detected in periphyton at frequencies up to 100% (EC23S857, Entero1, and GenBac3), 59.4% (HF183), and 21.9% (HumM2) confirming sequestration from the water column. Mean net flux shifts in water column inflow and outflow genetic indicator concentrations further supported interactions between the periphyton and water column under test conditions. In addition, positive correlations were observed between periphyton dry mass and genetic marker concentrations ranging from r = 0.693 (Entero1) to r = 0.911 (GenBac3). Overall, findings support the notion that genetic markers suspended in the water column can be trapped by periphyton suggesting that the benthic environment in flowing freshwater systems may be an important factor to consider for water quality management with molecular indicators.  

Description:

Periphyton is a complex mixture of algae, microbes, inorganic sediment, and organic matter that is attached to submerged surfaces in most flowing freshwater systems. This community is a key component of stream ecology and is also known to absorb pollutants from the water column, resulting in improved water quality. However, it remains uncertain what the role of periphyton is in the fate and transport of genetic fecal indicators suspended in the water column. An indoor mesocosm study was conducted to simultaneously measure genetic fecal indicators in the water column and in the associated periphyton when subject to wastewater point source loading. The experiment was conducted over 16-weeks and organized into periphyton colonization and wastewater loading periods. Treated waste water effluent was pumped directly from a treatment facility adjacent to the experimental stream facility. Inflow and outflow surface water grabs were paired with the collection of periphyton samples taken from the mesocosm substrates on a weekly basis. Samples were analyzed with three genetic fecal indicator qPCR assays targeting E. coli (EC23S857), enterococci (Entero1), and Bacteroidales (GenBac3), as well as, two human host-associated fecal pollution markers (HF183 and HumM2). In addition, periphyton dry mass was measured. During wastewater effluent loading, genetic markers were detected in periphyton at frequencies up to 100% (EC23S857, Entero1, and GenBac3), 59.4% (HF183), and 21.9% (HumM2) confirming sequestration from the water column. Mean net flux shifts in water column inflow and outflow genetic indicator concentrations further supported interactions between the periphyton and water column under test conditions. In addition, positive correlations were observed between periphyton dry mass and genetic marker concentrations ranging from r = 0.693 (Entero1) to r = 0.911 (GenBac3). Overall, findings support the notion that genetic markers suspended in the water column can be trapped by periphyton suggesting that the benthic environment in flowing freshwater systems may be an important factor to consider for water quality management with molecular indicators.  

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