Denitrification Gene Density Across a Wastewater-Impacted Riparian Buffer Zone.

Riparian buffers are a best management practice used extensively to protect water bodies from agriculturally-generated nitrate pollution. In particular, the biological process of denitrification has been shown to be a sink for this nitrate. Denitrification results in the reduction of nitrate under anoxic conditions to either nitrous oxide or dinitrogen gases in a multi-step enzymatic pathway. Despite the vast knowledge of the relationship between riparian buffers and denitrification, there is a paucity of information of the riparian buffer microbial community structure and composition which drives this biological process. Our studies, focused on a riparian buffer of the southeastern Coastal Plain, have demonstrated its importance in buffering a contiguous stream from the impact associated with an adjoining swine wastewater spray field. Using Real Time PCR analysis, we investigated the density of several genes involved in the nitrification and denitrification process and correlate them with incomplete and total denitrification using the denitrification enzyme assay. In particular, the gene density for nosZ, responsible for the conversion of nitrous oxide to dinitrogen gas was high, suggesting that most of the denitrification-related emissions should be attributable to complete denitrification.