A preliminary study on estimating extra-cellular nitrate reductase activities in estuarine systems

• Main Author: H.K. Pant
• Format: Article
• Language: English
• Published: EDP Sciences 2009-07-01
• Series: Knowledge and Management of Aquatic Ecosystems
• Subjects: nitrate reductase; estuarine waters; water quality; nitrous oxide
• Online Access: http://www.kmae-journal.org/index.php?option=article&access=standard&Itemid=129&url=/articles/kmae/pdf/2009/01/kmae09004.pdf

Enzymes catalyzing ammonium (NH4+)/nitrate (NO3–) into nitrous oxide (N2O)/molecular nitrogen (N2), play critical roles in water quality management. The objective of this paper was to investigate the role of extra-cellular enzymes in cycling of nitrogen (N) in aquatic systems. It appears that N in estuaries, salt marshes, etc., does not stay long enough to be available for uptake, thus, creating N limited conditions. This study showed that indigenous extra-cellular nitrate reductase along with others involved in N transformations in the waters/sediments of estuarine systems can cause complete removal of NH4+ and NO3– from the waters and available NH4+ and NO3– from the sediments. These results indicate that due to high extra-cellular nitrate reductase and other enzymes associated with N transformations in sediments/waters, substantial amounts of NH4+ and NO3– can be quickly lost from the systems as N2O and/or nitric oxide (NO), in turn, creating N limited conditions in estuarine systems. Such high activities of indigenous nitrate reductase and others are useful in removing readily bioavailable N from the systems, thereby avoidance of eutrophic conditions. However, they might contribute in increasing the N2O, a potent greenhouse gas with global warming potential (GWP) of 296, in the atmosphere.