Seasonal variations in nitrogen (N₂) fixation and denitrification rates were estimated in the sediment of Sundarban mangrove ecosystem, India. The mean rate of microbial N₂ fixation (16.53 ηmol N fixed/ hr/ g dry wt of sediment) was relatively higher than the mean rate of denitrification (14.72 ηmol N₂O-N /hr/dry wt of sediment) in the mangrove sediment throughout the study, suggesting satisfactory fertility of this ecoregion in terms of sediment nitrogen. Sediment from the deeper parts of this ecosystem showed higher N₂ fixation rate (18.23 ηmol N fixed/ hr/ g dry wt of sediment) than the surface sediment (10.17 ηmol N fixed/ hr/ g dry wt of sediment). Similar trend was observed for the denitrification rate in all the seasons. The ratio of N₂ fixation to denitrification rate showed an increasing trend with depth. The results depicted that under higher anoxic condition bacteria would prefer N₂ fixation over denitrification and would ultimately enhance the nitrogen storage capacity of this mangrove ecosystem. Although population of free living N₂ fixing bacteria decreased with increase in depth, the rate of N₂ fixation showed a reverse trend, during the study period. These results suggested that anoxic condition and low level of nitrate-nitrogen content could stimulate the enzyme activity responsible for N₂ fixation in this particular ecosystem.

中文翻译：

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探索印度桑达尔班红树林生态系统中的N2固定和反硝化过程

估计印度Sundarban红树林生态系统的沉积物中氮（N ₂）固定和反硝化速率的季节性变化。在整个红树林沉积物中，微生物固氮的平均速率（16.53ηmolN ₂固定/ hr / g沉积物干重）相对高于平均反硝化率（14.72ηmolN ₂ ON / hr /沉积物干重）。该研究表明，就沉积物氮而言，该生态区的肥力令人满意。来自该生态系统较深部分的沉积物显示出较高的N ₂固着率（18.23ηmolN固定/ hr / g沉积物干重）比表面沉积物（10.17ηmolN固定/ hr / g沉积物干重）。在所有季节中，反硝化率均观察到类似趋势。N ₂固着率与反硝化率的比值随深度的增加而增加。结果表明，在缺氧条件下，细菌会更喜欢N _2的固定而不是反硝化作用，并最终提高该红树林生态系统的氮存储能力。尽管自由生活的N ₂固定细菌的数量随着深度的增加而减少，但N ₂的发生率在研究期间，注视显示出相反的趋势。这些结果表明缺氧条件和低水平的硝酸盐-氮含量可以刺激在该特定生态系统中负责N ₂固定的酶活性。