Denitrification potential of the Northern Arabian Gulf--an experimental study.

The study aims to establish denitrification potential of the Northern Arabian Gulf (NAG), as nitrogen critically affects the ocean productivity, obliterates acidity, oxidative capacity and radiative transfer capability of atmosphere. The experimental study was conducted by taking cores from intertidal zones from two different sites in North and South, referred as sites N and S; representing two distinct environmental milieu. The experiment was conducted in controlled laboratory conditions simulating the tidal cycles. Multiple cores were taken and loaded with seawater with different N concentrations, the redox potential was established for each condition. Redox potential was significantly lower at 10 cm depth compared to the surface in all cores (P < 0.001). The redox potential at surface and at 10 cm depth was significantly lower at site S compared to site N (P < 0.001; F = 714.2), suggesting anaerobic sediments at site S. Effects of nitrate spiked seawater on denitrification under nonflooded and flooded conditions at the two sites were also studied. Three-way ANOVA analysis indicated that site, nitrate concentration, and flooding had significant main and interactive effects on the rate of denitrification. The results suggest that under ambient nitrate concentrations (0.03 mg NO(3)-N l(-1)), 6.3 ± 2.1 g NO(3)-N ha day can be denitrified by inter-tidal zone sediments. At a nitrate concentration of 1 mg NO(3)-N l(-1), 92 ± 16 g NO(3)-N ha day may be denitrified whilst at a very high nitrate load of 10 mg NO(3)-N l(-1), the sediments may attain a rate of denitrification close to 404 ± 78 g NO(3)-N ha day.