From Genes to Nitrogen Removal: Determining the Impacts of Poultry Industry Wastewater on Tidal Creek Denitrification

The intensification of the poultry industry in the last decades has led to a sharp increase in the number of animal processing plants discharging wastewater to water bodies. These discharges may have a significant effect on environmental quality and on important ecosystem functions, such as denitrification. We conducted a seasonal survey and a microcosm experiment in an impacted and a reference tidal creek to investigate the impacts of wastewater discharge from a poultry processing plant on sedimentary microbial communities, denitrification activity, and nitrate removal. Denitrification potential was measured using slurry incubations, and the microbial community was examined with 16S rDNA MiSeq sequencing and quantitative polymerase chain reaction of denitrification genes. The lowest denitrification rates were observed in the impacted creek, especially near the wastewater discharge, and denitrification inhibition by impacted creek water was clearly observed in the microcosm experiment. Denitrification rates were associated with changes in the microbial community composition and gene abundance. Estimated nitrate removal was lower in the impacted creek, and higher chlorophyll levels were observed in a downstream coastal bay through remote sensing. This study demonstrates denitrification inhibition by wastewater discharge from a poultry processing plant with potential consequences to coastal eutrophication.