Evidence of Genetic FecalMarker Interactions between Water Column and Periphytonin Artificial Streams

摘要

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 natural community is known to absorb pollutants from the water column, resulting in improved water quality. However, the role of periphyton in the fate and transport of genetic fecal markers suspended in the water column remains unclear. As application of genetic-based methodologies continues to increase in freshwater settings, it is important to identify any interactions that could potentially confound water quality interpretations. A 16 week indoor mesocosm study was conducted to simultaneously measure genetic fecal markers in the water column and in the associated periphyton when subject to wastewater source loading. Treated wastewater 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 quantitative real-time polymerase chain reaction assaystargeting Escherichia coli (EC23S857),enterococci (Entero1), and Bacteroidales (GenBac3),as well as, two human host-associated fecal pollution markers (HF183and HumM2). In addition, periphyton dry mass was measured. Duringwastewater effluent loading, genetic markers were detected in periphytonat frequencies up to 100% (EC23S857, Entero1, and GenBac3), 59.4%(HF183), and 21.9% (HumM2) confirming sequestration from the watercolumn. Mean net-flux shifts in water column inflow and outflow geneticindicator concentrations further supported interactions between theperiphyton and water column. In addition, positive correlations wereobserved between periphyton dry mass and genetic marker concentrationsranging from r = 0.693 (Entero1) to r = 0.911 (GenBac3). Overall, findings support the notion that geneticmarkers suspended in the water column can be trapped by periphyton,further suggesting that the benthic environment in flowing freshwatersystems may be an important factor to consider for water quality managementwith molecular methods.