Nutrient stoichiometry (N:P) controls nitrogen fixation and distribution of diazotrophs in a tropical eutrophic estuary
2020
Jabir, Thajudeen | Vipindas, Puthiya Veettil | Jesmi, Yousuf | Valliyodan, Sudheesh | Parambath, Prabhakaran Meethal | Singh, Arvind | Abdulla, Mohamed Hatha
Nitrogen fixation and its ecological regulation are poorly understood in the tropical estuaries, which are highly influenced by anthropogenic disturbances. In this study, we investigated the role of nutrient stoichiometry in the diversity, abundance and activity of N₂-fixing bacterial community and their seasonal variations in the water column of a tropical eutrophic estuary (Cochin estuary). The N₂ fixation rates in the estuary ranged from 0.1 to 2.0 nmol N₂ l⁻¹ h⁻¹, with higher activity during post-monsoon and lower during monsoon. The rates are appeared to be primarily controlled by dissolved inorganic nitrogen and phosphorous (N:P) ratio. Clone library analysis of nitrogenase (nifH) gene revealed that the major N₂ fixing phylotypes belong to Cluster I and Cluster III diazotrophs. The overall findings of this study suggest that monsoon induced seasonal changes in nutrient stoichiometry control the distribution and activity of diazotrophs in a tropical estuary.
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