Study Further Implicates Poultry Processing in Coastal Pollution
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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.
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