Nitrogen Uptake Rates during Spring in the NE Arabian Sea

Naveen Gandhi, R. Ramesh, R. Srivastava, M. S. Sheshshayee, R. M. Dwivedi, Mini Raman
2010 International Journal of Oceanography  
We present new data on N uptake rates and f-ratios in the north-eastern (NE) Arabian Sea, where significant amounts of Trichodesmium were present in spring, 2006. The measured total nitrogen uptake rates ranged from 0.34 to 1.58 mmol N . fixation associated with Trichodesmium varied from 0.002 to 0.54 mmol N estimated from the abundance of Trichodesmium and specific fixation rates of 1.5 pmol N trichome. Inclusion of fixation rates significantly changes f-ratios particularly in the coastal
more » ... in the coastal stations. Nitrogen isotopic data of surface suspended particles suggest that recently fixed nitrogen contributes as high as ~79% of the nitrogen in surface suspended particles. In addition, water column gained ~30 mmol N in the form of nitrate, likely due to nitrification of ammonium released by Trichodesmium. For better estimations, direct measurement of fixation is recommended.
doi:10.1155/2010/127493 fatcat:f4eq26q3tje6tnlrgrvym5snhe