Dinitrogen fixation rates in the Bay of Bengal during summer monsoon

• Published in: Environmental Research Communications
• Main Authors: Saxena, Himanshu, Sahoo, Deepika, Khan, Mohammad Atif, Kumar, Sanjeev, Sudheer, A K, Singh, Arvind
• Other Authors: DST-INSPIRE, Deapartment of Space
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: IOP Publishing 2020
• Subjects: Northwest Atlantic
• Online Access: http://dx.doi.org/10.1088/2515-7620/ab89fa; https://iopscience.iop.org/article/10.1088/2515-7620/ab89fa; https://iopscience.iop.org/article/10.1088/2515-7620/ab89fa/pdf

Abstract Biological dinitrogen (N 2 ) fixation exerts an important control on oceanic primary production by providing bioavailable form of nitrogen (such as ammonium) to photosynthetic microorganisms. N 2 fixation is dominant in nutrient poor and warm surface waters. The Bay of Bengal is one such region where no measurements of phototrophic N 2 fixation rates exist. The surface water of the Bay of Bengal is generally nitrate-poor and warm due to prevailing stratification and thus, could favour N 2 fixation. We commenced the first N 2 fixation study in the photic zone of the Bay of Bengal using 15 N 2 gas tracer incubation experiment during summer monsoon 2018. We collected seawater samples from four depths (covering the mixed layer depth of up to 75 m) at eight stations. N 2 fixation rates varied from 4 to 75 μ mol N m −2 d −1 . The contribution of N 2 fixation to primary production was negligible (<1%). However, the upper bound of observed N 2 fixation rates is higher than the rates measured in other oceanic regimes, such as the Eastern Tropical South Pacific, the Tropical Northwest Atlantic, and the Equatorial and Southern Indian Ocean.