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Arthur T Knackerbracket has found the following story:

by David Malmquist, The College of William & Mary

Excess nitrogen is a major threat to water quality in coastal waters worldwide. Found in treated wastewater, farm and lawn fertilizers and combustion exhaust, it fuels blooms of algae that shade submerged grasses and suck oxygen from the water when they die and decay.

A new study by researchers at William & Mary's Virginia Institute of Marine Science provides additional evidence that wastewater from a poultry processing plant has a particularly significant impact on water quality and nutrient cycling. That's because it contains not only lots of nitrogen, but antibiotics and byproducts of the process the plants use to treat their wastewater. These byproducts are thought to inhibit the growth and activity of microbes that would otherwise help remove nitrogen from tidal creeks before it can enter coastal systems.

The researchers, VIMS Ph.D. student Miguel Semedo and Professor Bongkeun Song, say their study is the first to evaluate poultry-industry impacts on water quality and nutrient cycling using genetic, microbial and remote-sensing techniques. Results of their work appear in the January issue of Environmental Science & Technology. The study was supported through the Fulbright Program and Semedo's graduate fellowship from Virginia Sea Grant.

Microbes remove nitrogen from aquatic ecosystems through a process called denitrification. "Microbes perform a number of ecosystem functions," says Semedo, now a post-doctoral researcher at the University of Porto's Interdisciplinary Centre of Marine and Environmental Research (CIIMAR) in Matosinhos, Portugal. "Denitrification is one of the most vital, as it has the potential to remove excess nitrogen from the system."

Denitrifying microbes have unique genes that control the denitrification process, a series of steps that transforms nitrate and nitrite—inorganic forms of nitrogen found in wastewater—into gaseous forms such as nitric oxide, nitrous oxide and dinitrogen. The latter compounds are unusable by most organisms and thus contribute little or nothing to over-fertilization of coastal waters.

Semedo and Song conducted the study in two tidal creeks on Virginia's Eastern Shore—one with a poultry processing plant in its headwaters and one without. The creeks drain into the coastal lagoons that lie between the mainland of the Delmarva Peninsula and its offshore barrier islands.

The pair measured nitrogen levels in the headwaters, middle, and mouth of each creek on four occasions between November 2016 and September 2017. They also collected sediment samples for laboratory analysis at VIMS, as denitrifying microbes generally live in muds on the creek bottom. In the lab, they identified the species of microbes present, noted which contained the genes known to control denitrification and subjected microbes from the uncontaminated "control" creek to water from the creek impacted by poultry-plant effluent.

Their field results showed clear evidence that nitrogen levels were higher in the contaminated creek.

"The levels of nitrate in the bottom waters of the impacted creek were significantly higher than those in the reference creek across all stations in most seasons," says Song.

"On average," adds Semedo, "nitrate levels in the impacted creek were 34 times higher at the headwaters station, 47 times higher at midstream, and 23 times higher near the mouth."

Journal Reference:

More information: Miguel Semedo et al. From Genes to Nitrogen Removal: Determining the Impacts of Poultry Industry Wastewater on Tidal Creek Denitrification, Environmental Science & Technology (2019). DOI: 10.1021/acs.est.9b03560

Original Submission