Denitrification in Aquatic and Marine Environments

Our interest in denitrification stems from our work with membrane inlet mass spectrometry and our development of an instrument that is capable of rapid, high precision measurements of dissolved gases (http://www.hpl.umces.edu/dga/DGAhome.htm).  The instrumentation allows for the direct measurement of N₂, the product of denitrification at the required precision of <0.1%.  Our work is currently focusing on denitrification associated with sediments in the Choptank River, a brackish subestuary of the Chesapeake Bay. 

Kana, T.M., M. B. Sullivan, J.C. Cornwell and K. Groszkowski. 1998. Denitrification in estuarine sediments determined by membrane inlet mass spectrometry. Limnol Oceanogr. 43:334-339.

Abstract

Steady-state and transient-state denitrification rates were measured in sediment cores from a brackish river of the Chesapeake Bay using high precision membrane inlet mass spectrometry. Denitrification was independent of salinity over the range of 1-13 ppt and directly dependent on nitrate concentration over the range of 0-200 µM in the overlying water. Denitrification was observed when the water colunm nitrate concentration was <1 µM, indicating that nitrification in the sediments was occurring. There was no detectable lag in the response of denitrification to an abrupt increase in nitrate in the overlying water column. Moreover, the enhanced rate under nitrate enrichment was either stable or changed slowly over periods of days. Thus, the microbial flora remained poised to utilize increased nitrate supplies, suggesting that the denitrifiers were facultative. An analysis based on diffusion theory supports a view that denitrification was controlled by properties that affected the physical transport of nitrate from the water to the sites of denitrification. Our results indicate that denitrification in this river can respond rapidly and directly to episodic events that cause changes in water column nitrate concentration.